[Federal Register Volume 76, Number 12 (Wednesday, January 19, 2011)]
[Proposed Rules]
[Pages 3392-3420]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-469]

[[Page 3391]]


Part IV

Department of the Interior


Fish and Wildlife Service


50 CFR Part 17

Endangered and Threatened Wildlife and Plants; Endangered Status for 
the Sheepnose and Spectaclecase Mussels; Proposed Rule

  Federal Register / Vol. 76 , No. 12 / Wednesday, January 19, 2011 / 
Proposed Rules  

[[Page 3392]]



Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R3-ES-2010-0050; MO 92210-0-0008-B2]
RIN 1018-AV93

Endangered and Threatened Wildlife and Plants; Endangered Status 
for the Sheepnose and Spectaclecase Mussels

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
list two freshwater mussels, the spectaclecase mussel (Cumberlandia 
monodonta) and sheepnose (Plethobasus cyphyus) as endangered under the 
Endangered Species Act of 1973, as amended (Act). If we finalize this 
rule as proposed, it would extend the Act's protections to these 
species throughout their ranges, including sheepnose in Alabama, 
Illinois, Indiana, Iowa, Kentucky, Minnesota, Mississippi, Missouri, 
Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin, 
and spectaclecase in Alabama, Arkansas, Illinois, Indiana, Iowa, 
Kentucky, Kansas, Minnesota, Missouri, Nebraska, Ohio, Tennessee, 
Virginia, West Virginia, and Wisconsin. We determined that critical 
habitat for these species is prudent, but not determinable at this 
time. The Service seeks data and comments from the public on this 
proposed listing rule.

DATES: We will consider comments and information we receive from all 
interested parties by March 21, 2011. We must receive requests for 
public hearings, in writing, at the address shown in the FOR FURTHER 
INFORMATION CONTACT section by March 7, 2011.

ADDRESSES: You may submit comments by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the instructions for submitting comments on docket number FWS-
     U.S. mail or hand-delivery: Public Comments Processing, 
Attn: FWS-R3-2010-0050; Division of Policy and Directives Management; 
U.S. Fish and Wildlife Service; 4401 North Fairfax Drive, Suite 222; 
Arlington, VA 22203.
    We will post all comments on http://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see Public Comments section below for more information).

FOR FURTHER INFORMATION CONTACT: Richard Nelson, Field Supervisor, at 
the U.S. Fish and Wildlife Service, Rock Island, Illinois Ecological 
Services Field Office, 1511 47th Avenue, Moline, IL 61265 (telephone 


Public Comments

    Our intent is to use the best available commercial and scientific 
data as the foundation for all endangered and threatened species 
classification decisions. We request comments or suggestions from other 
concerned governmental agencies, the scientific community, industry, or 
any other interested party concerning this proposed rule to list the 
spectaclecase and sheepnose mussels as endangered. We particularly seek 
comments concerning:
    (1) Biological, commercial trade, or other relevant data concerning 
any threats (or lack thereof) to the species and regulations that may 
be addressing those threats.
    (2) Additional information concerning the ranges, distributions, 
and population sizes of the species, including the locations of any 
additional populations of these species.
    (3) Any additional information on the biological or ecological 
requirements of these species.
    (4) Current or planned activities in the areas occupied by these 
species and possible impacts of these activities on the species and 
their habitats.
    (5) Potential effects of climate change on these species and their 
    (6) The reasons why areas should or should not be designated as 
critical habitat as provided by section 4 of the Act (16 U.S.C. 1531 et 
seq.), including whether the benefits of designation would outweigh 
threats to the species that designation could cause (e.g., exacerbation 
of existing threats, such as overcollection), such that the designation 
of critical habitat is prudent.
    (7) Specific information on:
     What areas contain physical and biological features 
essential for the conservation of these species;
     What areas are essential to the conservation of these 
species and
     Special management considerations or protection that 
proposed critical habitat may require.
    Please note that submissions merely stating support for or 
opposition to the action under consideration without providing 
supporting information, although noted, will not be considered in 
making a determination, as section 4(b)(1)(A) of the Act directs that 
determinations as to whether any species is an endangered or threatened 
species must be made ``solely on the basis of the best scientific and 
commercial data available.''
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. We will not 
accept comments sent by e-mail or fax or to an address not listed in 
the ADDRESSES section. Comments must be submitted to http://www.regulations.gov before 11:59 (Eastern Time) on the date specified 
in the DATES section. We will not consider hand-delivered comments that 
we do not receive, or mailed comments that are not postmarked, by the 
date specified in the DATES section.
    We will post your entire comment--including your personal 
identifying information--on http://www.regulations.gov. If you provide 
personal identifying information in your comment, you may request at 
the top of your document that we withhold this information from public 
review. However, we cannot guarantee that we will be able to do so.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on http://www.regulations.gov, or by 
appointment, during normal business hours at the Rock Island, Illinois 
Ecological Services Field Office (see the FOR FURTHER INFORMATION 
CONTACT section).

Public Hearing

    The Act provides for one or more public hearings on this proposal, 
if requested. Requests must be received by March 7, 2011. Such requests 
must be made in writing and be addressed to the Field Supervisor at the 
address provided in the FOR FURTHER INFORMATION CONTACT section. We 
will schedule public hearings on this proposal, if any are requested, 
and announce the dates, times, and places of those hearings, as well as 
how to obtain reasonable accommodations, in the Federal Register and 
local newspapers at least 15 days before the hearing.
    Persons needing reasonable accommodations to attend and participate 
in a public hearing should contact the Rock Island, Illinois Ecological 
Services Field Office by telephone at 309-757-5800, as soon as 
possible. To allow sufficient time to process requests, please call no 
later than one week before the hearing date. Information regarding this 
proposed rule is available in alternative formats upon request.

[[Page 3393]]


Species Descriptions

    The spectaclecase (Cumberlandia monodonta) is a member of the 
mussel family Margaritiferidae and was originally described as Unio 
monodonta Say, 1829. The type locality is the Falls of the Ohio (on the 
Ohio River in the vicinity of Louisville, Kentucky, and adjacent 
Indiana), and the Wabash River (probably the lower portion in Illinois 
and Indiana) (Parmalee and Bogan 1998, p. 49). Parmalee and Bogan 
(1998, p. 49) summarized the synonymy of the spectaclecase. The species 
has been placed in the genera Unio, Margaritana, Alasmidonta, 
Margarita, Margaron, and Margaritifera at various times in history. 
Ortmann (1912, p. 13) placed it in the monotypic (a taxonomic group 
with only one biological type) genus Cumberlandia in the family 
Margaritiferidae. Currently recognized synonymy includes Unio 
soleniformis (Lea). Smith (2001, p. 43) reassigned the spectaclecase to 
the Holarctic genus Margaritinopsis based on shell and gill characters. 
However, the Service will defer to the Committee on Scientific and 
Vernacular Names of Mollusks of the Council of Systematic 
Malacologists, American Malacological Union (Turgeon et al. 1998), on 
whether the genus Margaritinopsis is accepted as valid for the 
spectaclecase. Until an official decision is made, the Service will use 
the commonly accepted Cumberlandia for the genus of this species. 
Spectaclecase is the accepted common name for Cumberlandia monodonta 
(Turgeon et al. 1998, p. 32).
    The spectaclecase is a large mussel that reaches at least 9.25 
inches (23.5 centimeters (cm)) in length (Havlik 1994, p. 19). The 
shape of the shell is greatly elongated, sometimes arcuate (curved), 
and moderately inflated, with the valves being solid and moderately 
thick, especially in older individuals (Parmalee & Bogan 1998, p. 49). 
Both anterior and posterior ends of the shell are rounded with a 
shallow depression near the center of shell (Baird 2000, p. 6; Parmalee 
& Bogan 1998, p. 49). The anterior end is higher than the posterior end 
(Baird 2000, p. 6). The posterior ridge is low and broadly rounded 
(Parmalee & Bogan 1998, p. 50). Year-one specimens have heavy ridges 
running parallel with the growth arrests, which are shell lines that 
indicate slower periods of growth, thought to be laid down annually 
(Baird 2000, p. 6). The periostracum (external shell surface) is 
somewhat smooth, rayless, and light yellow, greenish-tan, or brown in 
young specimens, becoming rough and dark brown to black in old shells 
(Parmalee & Bogan 1998, p. 50). The shell commonly will crack 
posteriorly when dried (Oesch 1984, p. 31).
    Internally, the single pseudocardinal tooth (a triangular tooth-
like structure along the hinge line of the internal portion of the 
shell) is simple and peg-like in the right valve, fitting into a 
depression in the left (Parmalee & Bogan 1998, p. 50). The lateral 
teeth are straight and single in the right valve, and double in the 
left valve but become fused with age into an indistinct raised hinge 
line (Parmalee & Bogan 1998, p. 50). The soft anatomy was described by 
Williams et al. (2008, pp. 497-498). The color of the nacre (interior 
covering of the shell) is white, occasionally granular and pitted, 
mostly iridescent in young specimens, but becoming iridescent 
posteriorly in older shells (Parmalee & Bogan 1998, p. 50). There are 
no differences between the sexes in the shells of this species (Baird 
2000, p. 19). Key characters for distinguishing the spectaclecase from 
other mussels are its large size, elongate shape, arcuate ventral 
margin, dark coloration, roughened periostracum, poorly developed 
teeth, and white nacre (Oesch 1984, pp. 31-32). No other North American 
mussel species has this suite of characters.
    The sheepnose (Plethobasus cyphyus) is a member of the mussel 
family Unionidae and was originally described as Obliquaria cyphya 
Rafinesque, 1820. The type locality is the Falls of the Ohio (Parmalee 
& Bogan 1998, p. 175) on the Ohio River in the vicinity of Louisville, 
Kentucky, and adjacent Indiana. Parmalee and Bogan (1998, p. 175) 
summarized the synonymy of the species. Over the years, the name of 
this species has been variably spelled cyphya, scyphius, cyphius, 
cyphia, cyphyum, and ultimately cyphyus. Over the years the species has 
been placed in the genera Obliquaria, Unio, Pleurobema, Margarita, and 
Margaron. It was ultimately placed in the genus Plethobasus by Ortmann 
(1919, pp. 65-66) where it remains today (Turgeon et al. 1998, p. 35). 
The Service recognizes Unio aesopus and U. compertus as synonyms of 
Plethobasus cyphyus. Sheepnose is the accepted common name for 
Plethobasus cyphyus as established by the Committee on Scientific and 
Vernacular Names of Mollusks of the Council of Systematic 
Malacologists, American Malacological Union (Turgeon et al. 1998, p. 
35). The Service also recognizes ``bullhead'' and ``clear profit'' as 
older common names for the sheepnose.
    Key characters useful for distinguishing the sheepnose from other 
mussels are its color, the occurrence of central tubercles, and its 
general shape. Oesch (1984, p. 120) and Parmalee and Bogan (1998, p. 
176), describe the sheepnose as a medium-sized mussel that reaches 
nearly 5 inches (13 cm) in length. The shell is elongate ovate in 
shape, moderately inflated, and with thick, solid valves. The anterior 
end of the shell is rounded, but the posterior end is somewhat bluntly 
pointed to truncate. The dorsal margin of the shell is nearly straight, 
while the ventral margin is uniformly rounded or slightly convex. The 
posterior ridge is gently rounded, becoming flattened ventrally and 
somewhat biangular. There is a row of large, broad tubercular swellings 
on the center of the shell extending from the beak to the ventral 
margin. A broad, shallow sulcus (depression on furrow on the outside 
surface of shell) lies between the posterior ridge and central row. 
Beaks are elevated, high, and placed near the anterior margin. Juvenile 
beak sculpture consists of a few concentric ridges at the tip of the 
beaks. The periostracum is generally smooth, shiny, rayless, and light 
yellow to a dull yellowish brown. Concentric ridges resulting from 
growth arrests are usually darker.
    Oesch (1984, p. 120) describes the internal anatomy of the 
sheepnose as the left valve having two heavy, erect, roughened, 
somewhat triangular, and divergent pseudocardinal teeth. The right 
valve has a large, triangular, roughened pseudocardinal tooth. The 
lateral teeth are heavy, long, slightly curved, and serrated. The beak 
cavity is shallow to moderately deep. The soft anatomy was described by 
Williams et al. (2008, p. 94). The color of the nacre is generally 
white, but may be pinkish to cream-colored and iridescent posteriorly. 
There are no differences between the sexes in the shells of this 
species. The shell of the sheepnose is extremely hard and was given the 
name ``clear profit'' by early commercial shellers, being too hard to 
cut into buttons (Wilson & Clark 1914, p. 57). The species also 
preserves well in archaeological material (Morrison 1942, p. 357).

Life History

    The general biology of the spectaclecase and sheepnose are similar 
to other bivalve mollusks belonging to the families Margaritiferidae 
and Unionidae, order Unioniformes or Unionoida. Adult mussels 
suspension-feed, spending their entire lives partially or completely 
buried within the substrate (Murray and Leonard 1962, p. 27). Adults 
feed on algae, bacteria, detritus, microscopic animals, and dissolved 
organic material (Christian et

[[Page 3394]]

al. 2004, pp. 108-109; Nichols & Garling 2000, p. 873; Silverman et al. 
1997, p. 1859; Strayer et al. 2004, pp. 430-431). Recent evidence 
suggests that adult mussels may also deposit feed on particles in the 
sediment (Raikow & Hamilton 2001, p. 520). For their first several 
months, juvenile mussels employ foot (pedal) feeding, consuming 
bacteria, algae, and detritus (Yeager et al. 1994, p. 221).
    As a group, mussel longevity varies tremendously with some species 
living only about 4 years (Haag & Rypel 2010, p. 5) but possibly up to 
100 to 200 years in other species (Ziuganov et al. 2000, p. 102). 
However, the vast majority of species live a few decades (Haag & Rypel 
2010, pp. 4-6). Baird (2000, pp. 54, 59, 67) aged 278 specimens of the 
spectaclecase in Missouri by sectioning the hinge ligament, as most 
margaritiferids are aged. The maximum age determined was 56 years, but 
he surmised that some large individuals may have been older. A very 
large specimen (9.25 inches (23.5 cm)) from the St. Croix River, 
Minnesota and Wisconsin, was estimated (based on external growth ring 
counts) to be approximately 70 years old (Havlik 1994, p. 19). 
Sheepnose longevity has been reported as being nearly 30 years (Watters 
et al. 2009, p. 221). Thick shelled mussels from large rivers, like 
sheepnose, are thought to live longer than other species (Stansbery 
1961, p. 16).
    Mussels tend to grow relatively rapidly for the first few years, 
and then slow appreciably at sexual maturity, when energy presumably is 
being diverted from growth to reproductive activities (Baird 2000, pp. 
66-67). In spectaclecase, the biggest change in growth rate appears to 
occur at 10 to15 years of age, which suggests that significant 
reproductive investment does not occur until they reach 10 years of age 
(Baird 2000, pp. 66-67).
    Margaritiferids and unionids have an unusual mode of reproduction. 
With very few exceptions, their life cycle includes a brief, obligatory 
parasitic stage on a host organism, typically fish. Eggs develop into 
microscopic larvae (glochidia) within special gill chambers of the 
female. The female expels the mature glochidia, which must attach to an 
appropriate host species (generally a fish) to complete development. 
Host specificity varies among margaritiferids and unionids. Some 
species appear to use a single host, while others can transform on 
several host species. Following successful infestation, glochidia 
encyst (enclose in a cyst-like structure), remain attached to the host 
for several weeks, and then drop off as newly transformed juveniles. 
For further information on the life history of freshwater mussels, see 
Williams et al. 2008.
    Mussel biologists know relatively little about the specific life-
history requirements of the spectaclecase and sheepnose. Most mussels, 
including the spectaclecase and sheepnose, have separate sexes. Age at 
sexual maturity of the spectaclecase was estimated to be 4 to 5 years 
for males and 5 to 7 years for females, with sex ratios approximating 
50:50 (Baird 2000, p. 24). The spectaclecase life cycle includes a 
parasitic phase; however, despite extensive investigation, the host 
species is not yet known. The spectaclecase is thought to release 
glochidia from early April to late May in the Meramec and Gasconade 
Rivers, Missouri (Baird 2000, p. 26). Gordon and Smith (1990, p. 409) 
reported the species as producing two broods, one in spring or early 
summer and the other in the fall, also based on Meramec River 
specimens. In the Meramec and Gasconade Rivers, however, Baird (2000, 
pp. 26-27) found no evidence of two spawns in a given year.
    Age at sexual maturity for the sheepnose is unknown, but given its 
estimated longevity, probably occurs after a few years. The sheepnose 
is thought to be a short-term brooder, with egg fertilization taking 
place in early summer (Parmalee & Bogan 1998, p. 177; Williams et al. 
1998, p. 498), and glochidial release presumably occurring later in the 
summer. Hermaphroditism occurs in many mussel species (van der Schalie 
1966, p. 77), but is not known for the sheepnose. If hermaphroditism 
does occur in the sheepnose, it may explain the occurrence of small, 
but persistent populations over long periods of time.
    Glochidia of spectaclecase and sheepnose are released in 
conglutinates (gelatinous structures containing numerous glochidia and 
analogous to cold capsules). Spectaclecase glochidia lack hooks (teeth-
like structures that presumably function to pierce through skin tissue 
of the host) and are the smallest glochidia known of any North American 
freshwater mussel; they measure approximately 0.0024 inches (0.06 mm) 
in both length and height (Baird 2000, p. 22). Tens to hundreds of 
thousands of glochidia may occur in each conglutinate. Based on eight 
Missouri spectaclecase specimens, the number of conglutinates released 
per female varied from 53 to 88, with a mean of 64.5 (Baird 2000, p. 
23). Total fecundity (reproductive potential, including glochidia and 
ova) in Baird's (2000, p. 27) Missouri study varied from 1.93 to 9.57 
million per female. In mussels, fecundity is related positively to body 
size and inversely related to glochidia size (Bauer 1994, pp. 940-941). 
The reproductive potential of the spectaclecase is therefore 
phenomenal. However, the fact that extant populations are generally 
skewed towards larger adults strongly indicates that survival rates to 
the adult stage must be extraordinarily low.
    Researchers in Wisconsin observed female spectaclecase under 
boulders in the St. Croix River simultaneously releasing their 
conglutinates (Heath 2008, pers. comm.). The spectaclecase 
conglutinates are entrained along a transparent, sticky mucous strand 
up to several feet in length (Lee & Hove 1997, p. 9). Baird (2000, p. 
29) observed the release of loose glochidia and small fragments of 
conglutinates. Based on his observations, he hypothesized that 
conglutinates sometimes contain mostly immature glochidia, and that 
conglutinates containing mostly immature glochidia may be aborted when 
    Sheepnose conglutinates are narrow and lanceolate in outline, solid 
and red or pink in color, and discharged in unbroken form (Oesch 1984, 
pp. 118-119). Discharge of sheepnose conglutinates have been observed 
in late July (Ortmann 1911, p. 306) and August (Williams et al. 2008, 
p. 498). Ortmann (1911, p. 306) described them as being pink and 
``lying behind the posterior end of the shell, which were greedily 
devoured by a number of minnows.'' Sheepnose glochidia are semicircular 
in outline, with the ventral margin obliquely rounded, hinge line long, 
and medium in size. The length (0.009 inches (0.23 mm)) is slightly 
greater than the height (0.008 inches (0.20 mm)) (Oesch 1984, p. 119). 
Several hundred glochidia probably occur in each conglutinate. Judging 
from the size of the glochidia, total fecundity (including glochidia 
and ova) per female sheepnose is probably in the tens of thousands.
    Like many freshwater mussels, the complex life histories of the 
spectaclecase and sheepnose have many vulnerable components that may 
prevent successful reproduction or recruitment of juveniles into 
existing populations. Glochidia must come into contact with a specific 
host species for their survival to be ensured. Without the proper host, 
the glochidia will perish. The host(s) for the spectaclecase is 
unknown, although over 60 species of fish, amphibians, and crayfish 
have been tested in the lab during host suitability studies (Baird 
2000, pp. 23-24; Henley & Neves 2006, p. 3; Hove et al. 2009b, pp. 22-
23; Hove et al. 1998,

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pp. 13-14; Hove et al. 2008, p. 4; Knudsen & Hove 1997, p. 2; Lee & 
Hove 1997, pp. 9-10). Two of 690 wild-collected fish checked by Baird 
(2000, p. 24) had spectaclecase glochidia attached to their gills; 
these fish were the bigeye chub (Hybopsis amblops) and pealip redhorse 
(Moxostoma pisolabrum). However, these fish are not confirmed as hosts, 
because the encysted glochidia had not grown measurably and glochidial 
transformation was not observed (Baird 2000, p. 24). Spectaclecase 
populations are oftentimes highly aggregated (see Habitat) with many 
apparently even-aged individuals, suggesting that glochidia may excyst 
simultaneously from a host (Gordon & Layzer 1989, p. 19). Additional 
host work is underway to test the wild-collected fish species that were 
found with encysted spectaclecase glochidia (pealip redhorse and bigeye 
chub), as well as to test additional species of fish and other aquatic 
organisms for suitability. Host information is needed so that existing 
populations can be artificially cultured for potential population 
augmentation and reintroduction efforts.
    Little is known regarding host fish of the sheepnose. Until 
recently the only cited host for this species came from a 1914 report 
that found glochidia naturally attached to sauger (Sander canadense) in 
the wild. No confirmation of successful transformation was recorded in 
this early report (Surber 1912, p. 110; Wilson 1914, pp. 338-340). 
However, recent laboratory studies at the Genoa National Fish Hatchery, 
the University of Minnesota, and Ohio State University have 
successfully transformed sheepnose glochidia on fathead minnow 
(Pimephales promelas), creek chub (Semotilus atrromaculatus), central 
stoneroller (Campostoma anomalum), and brook stickleback (Culaea 
inconstans) (Watters et al. 2005, pp. 11-12; Brady 2008, pers. comm.; 
Watters 2008, pers. comm.). Although these are identified as suitable 
hosts in laboratory studies, natural interactions between the 
aforementioned fishes and the sheepnose seem rare and infrequent due to 
habitat preferences. Fish that frequent medium to large rivers near 
mussel beds, like the sauger, may act as hosts in the natural 


    The spectaclecase generally inhabits large rivers, and is found in 
microhabitats sheltered from the main force of current. It occurs in 
substrates from mud and sand to gravel, cobble, and boulders in 
relatively shallow riffles and shoals with a slow to swift current 
(Baird 2000, pp. 5-6; Buchanan 1980, p. 13; Parmalee & Bogan 1998, p. 
50). According to Stansbery (1967, pp. 29-30), this species is usually 
found in firm mud between large rocks in quiet water very near the 
interface with swift currents. Specimens have also been reported in 
tree stumps, in root masses, and in beds of rooted vegetation (Oesch 
1984, p. 33). Similar to other margaritiferids, spectaclecase 
occurrences throughout much of its range tend to be aggregated (Gordon 
& Layzer 1989, p. 19), particularly under slab boulders or bedrock 
shelves (Baird 2000, p. 6; Buchanan 1980, p. 13; Parmalee & Bogan 1998, 
p. 50), where they are protected from the current. Up to 200 specimens 
have been reported from under a single large slab in the Tennessee 
River at Muscle Shoals, Alabama (Hinkley 1906, p. 54). Unlike most 
species that move about to some degree, the spectaclecase may seldom if 
ever move except to burrow deeper and may die from stranding during 
droughts (Oesch 1984, p. 17).
    The sheepnose is primarily a larger-stream species occurring 
primarily in shallow shoal habitats with moderate to swift currents 
over coarse sand and gravel (Oesch 1984, p. 121). Habitats with 
sheepnose may also have mud, cobble, and boulders. Sheepnose in larger 
rivers may occur at depths exceeding 6 m (Williams et al. 2008, p. 


    A recent genetic study (Monroe et al. 2007, pp. 7-13) indicates 
that much of the remaining genetic variability in the spectaclecase is 
represented in each of the remaining large populations, and that these 
populations do not appear to differ significantly from one another. 
Genetics studies of sheepnose are currently under investigation; 
however, no conclusions were available at the time of publication (Roe 
2010, pers. comm.).

Species Distribution

    We use the term ``population'' here in a geographical and not 
genetic sense, defining it as all individuals of the spectaclecase or 
sheepnose living in one stream. Using the term in this way allows the 
status, trends, and threats to be discussed comparatively across 
streams where the species occur. In using this term we do not imply 
that their populations are currently reproducing and recruiting or that 
they are distinct genetic units. We considered populations of the 
spectaclecase and sheepnose as extant if live or fresh-dead specimens 
have been observed or collected since 1990. A ``population cluster'' 
refers to where two or more adjacent stream populations of a species 
occur without a barrier (for example, a dam and impoundment) between 
    Following are generalized sets of criteria that were used to 
categorize the relative status of populations of spectaclecase and 
sheepnose. The status of a population is considered ``improving'' if: 
(1) There is evidence that habitat degradation appears insignificant, 
(2) live or fresh dead mussel abundance has improved during post-1990 
surveys, or (3) ample evidence of recent recruitment has been 
documented during post-1990 surveys. The status of a population is 
considered ``stable'' if: (1) There is little evidence of significant 
habitat loss or degradation, (2) live or fresh dead mussel abundance 
has been fairly consistent during post-1990 surveys, or (3) evidence of 
relatively recent recruitment has been documented during post-1990 
surveys. The status of a population is considered ``declining'' if: (1) 
There is ample evidence of significant habitat loss or degradation, (2) 
live or fresh dead mussel numbers have declined during recent surveys, 
or (3) no evidence of relatively recent recruitment has been documented 
during recent surveys. The status of a population is considered 
``extirpated'' if: (1) All known suitable habitat has been destroyed, 
or (2) no live or fresh dead mussels of any age have been located 
during recent surveys. The status of a population is considered 
``unknown'' if the available information is inadequate to place the 
population in one of the above four categories. In a few cases, 
additional information not listed above may have been used to 
categorize a population.

Spectaclecase Historical Range and Distribution

    The spectaclecase occurred historically in at least 44 streams in 
the Mississippi, Ohio, and Missouri River basins (Butler 2002a, p. 6, 
Heath 2008, pers. comm.). Its distribution comprised portions of 15 
States (Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, 
Minnesota, Missouri, Nebraska, Ohio, Tennessee, Virginia, West 
Virginia, and Wisconsin). Historical occurrence by stream system (with 
tributaries) include the: upper Mississippi River system (Mississippi 
River (St. Croix, Chippewa, Rock, Salt, Illinois (Des Plaines, Kankakee 
Rivers), Meramec (Bourbeuse, Big Rivers), Kaskaskia Rivers; Joachim 
Creek)); lower Missouri River system (Missouri River (Platte, River Aux 
Vases, Osage (Sac, Marais des Cygnes Rivers), Gasconade (Osage Fork, 
Big Piney River) Rivers)); Ohio River system (Ohio River

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(Muskingum, Kanawha, Green, Wabash Rivers)); Cumberland River system 
(Cumberland River (Big South, Caney Fork; Stones, Red Rivers)); 
Tennessee River system (Tennessee River (Holston, Nolichucky, Little, 
Little Tennessee, Clinch (Powell River), Sequatchie, Elk, Duck 
Rivers)); lower Mississippi River system (Mulberry, Ouachita Rivers).

Spectaclecase Current Range and Distribution

    Extant populations of the spectaclecase are known from 19 streams 
in 11 States (Butler 2002b, p. 7). These include the following stream 
systems (with tributaries):
     Upper Mississippi River system (Mississippi River (St. 
Croix, Meramec (Bourbeuse, Big Rivers) Rivers));
     Lower Missouri River system (Sac and Gasconade (Osage 
Fork, Big Piney River) Rivers);
     Lower Ohio River system (lowermost Ohio River (Kanawha, 
Green Rivers));
     Cumberland River system (Cumberland River);
     Tennessee River system (Tennessee River (Nolichucky, 
Clinch, Duck Rivers)); and
     Lower Mississippi River system (Mulberry, Ouachita 
    The 19 extant spectaclecase populations occur in the following 11 
States (with streams):
     Alabama (Tennessee River),
     Arkansas (Mulberry, Ouachita Rivers),
     Illinois (Mississippi, Ohio Rivers),
     Iowa (Mississippi River),
     Kentucky (Ohio, Green Rivers),
     Minnesota (Mississippi, St. Croix Rivers),
     Missouri (Mississippi, Meramec, Bourbeuse, Big, Gasconade, 
Sac, Big Piney Rivers; Osage Fork),
     Tennessee (Tennessee, Clinch, Nolichucky, Duck Rivers; 
Caney Fork),
     Virginia (Cumberland, Clinch Rivers),
     West Virginia (Kanawha River), and
     Wisconsin (Mississippi, St. Croix Rivers).

Spectaclecase Population Estimates and Status

    Based on historical and current data, the spectaclecase has 
declined significantly rangewide and is now known from only 19 of 44 
streams (Table 1), representing a 57 percent decline. The species is 
presumed extirpated from thousands of river miles and from numerous 
reaches of habitat in which it occurred historically, including long 
reaches of upper Mississippi, Ohio, Cumberland, and Tennessee Rivers 
and many other streams and stream reaches. Of the 19 extant 
populations, 6 are represented by only one or two recent specimens each 
and are likely declining and some may be extirpated. Populations in 
Mississippi and Clinch Rivers have recently experienced significant 
population declines. Most surviving populations face significant 
threats and with few exceptions are highly fragmented and restricted to 
short stream reaches. The spectaclecase is considered extirpated from 
Indiana, Kansas, Nebraska, and Ohio. The only relatively strong 
populations remaining are in the Meramec and Gasconade Rivers in 
Missouri and in the St. Croix River in Minnesota and Wisconsin.

                Table 1--Spectaclecase Status in All Streams of Historical or Current Occurrence
                                                                           Date of Last Live
           River Basin                  Stream          Current Status        Observation          Comments
Upper Mississippi River.........  Mississippi River.  declining.........  2009..............  ..................
                                  St. Croix River...  stable............  2008..............  ..................
                                  Chippewa River....  extirpated........  1989..............  ..................
                                  Rock River........  extirpated........  ~1970.............  ..................
                                  Salt River........  extirpated........  1980..............  ..................
                                  Illinois River....  extirpated........  ~1914.............  ..................
                                  Des Plaines River.  extirpated........  ~1921.............  ..................
                                  Kankakee River....  extirpated........  1906..............  ..................
                                  Meramec River.....  stable............  2003..............  ..................
                                  Bourbeuse River...  stable............  1997..............  ..................
                                  Big River.........  stable............  2002..............  ..................
                                  Kaskaskia River...  extirpated........  ~1970.............  ..................
                                  Joachim Creek.....  extirpated........  ~1965.............  ..................
Lower Missouri River............  Missouri River....  extirpated........  ~1914.............  ..................
                                  Platte River......  extirpated........  ~1917.............  ..................
                                  River Aux Vases...  extirpated........  ~1974.............  ..................
                                  Osage River.......  extirpated........  1980..............  ..................
                                  Sac River.........  declining.........  2001..............  ..................
                                  Marais des Cygnes   extirpated........  unknown...........  relic shell
                                   River.                                                      observed in 1998.
                                  Gasconade River...  stable............  2007..............  ..................
                                  Big Piney River...  unknown...........  2004..............  ..................
                                  Osage Fork........  unknown...........  1999..............  ..................
Ohio River......................  Ohio River........  declining.........  1994..............  single individual
                                  Muskingum River...  extirpated........  unknown...........  relic shell
                                                                                               observed in 1995.
                                  Kanawha River.....  unknown...........  2005..............  two live
                                  Green River.......  unknown...........  2006..............  ..................
                                  Wabash River......  extirpated........  1970..............  ..................
Cumberland River................  Cumberland River..  unknown...........  2008..............  single individual
                                  Big South Fork....  extirpated........  1911..............  ..................
                                  Caney Fork........  extirpated........  1988..............  ..................
                                  Stones River......  extirpated........  1968..............  ..................
                                  Red River.........  extirpated........  1966..............  ..................
Tennessee River.................  Tennessee River...  unknown...........  2001..............  ..................
                                  Holston River.....  extirpated........  1981..............  ..................
                                  Nolichucky River..  unknown...........  1991..............  ..................

[[Page 3397]]

                                  Little River......  extirpated........  ~1911.............  ..................
                                  Little Tennessee    extirpated........  unknown...........  relic shell
                                   River.                                                      observed in 1980,
                                                                                               previous record
                                  Clinch River......  declining.........  2005..............  ..................
                                  Powell River......  extirpated........  ~1978.............  ..................
                                  Sequatchie River..  extirpated........  ~1925.............  ..................
                                  Elk River.........  extirpated........  unknown...........  relic shell
                                                                                               observed in 1998.
                                  Duck River........  declining.........  1999..............  single individual
Lower Mississippi River.........  Mulberry River....  unknown...........  ~1995.............  single individual
                                  Ouachita River....  declining.........  2000..............  two individuals

    Based on collections made over 100 years ago, the spectaclecase was 
historically widespread and locally common in many streams rangewide. 
The spectaclecase is often absent from archaeological shell middens 
(Morrison 1942, p. 353) and is generally difficult to find due to its 
habit of occurring under rocks or ledges and burrowing deep into the 
substrate (Parmalee 1967, p. 25). Therefore, the chance of casually 
finding the species where population numbers are low is remote.
    The spectaclecase was considered a rare species by mussel experts 
as early as 1970 (Stansbery 1970, p. 13), when the first attempt was 
made to compile a list of imperiled mussels. The spectaclecase is 
considered widely distributed but absent from many areas where it 
formerly occurred (Cummings & Mayer 1992, p. 22). The American 
Malacological Union and American Fisheries Society consider the 
spectaclecase to be threatened (Williams et al. 1993, p.10). Six of the 
19 streams (or big river reaches) considered to harbor extant 
populations of the spectaclecase are represented by one or two recent 
specimens (for example, Ohio, Kanawha, Cumberland, Duck, Ouatchita, and 
Mulberry Rivers), exemplifying the species' imperiled status rangewide.
    In some streams, the last reported records for the spectaclecase 
occurred decades ago (for example, Rock, Des Plaines, Kaskaskia, 
Platte, Wabash, Stones, Red, and Little Rivers; River Aux Vases; Big 
South Fork). Parmalee (1967, p. 25) considered the spectaclecase to be 
``rare and of local occurrence'' in Illinois in the 1960s, but that it 
had ``[a]pparently already been extirpated from the Illinois and 
Kankakee Rivers.'' The only records known from some streams are relic 
specimens collected around 1975 (for example, Marais des Cygnes, 
Muskingum, and Elk Rivers).
    Although quantitative historical abundance data for the 
spectaclecase is rare, generalized relative abundance (the percent 
abundance of a species, divided by the total abundance of all mussel 
species combined) was sometimes noted in the historical literature and 
can be inferred from museum lots. The following is a summary of what is 
known about the relative abundance and trends of presumably extant 
spectaclecase populations by stream system.

Upper Mississippi River System

    The spectaclecase was historically known from 13 streams in the 
upper Mississippi River system. Currently, only four streams in the 
system are thought to have extant spectaclecase populations.
    Mississippi River mainstem: In 1907, Bartsch found spectaclecase at 
approximately nine of the 140 sampled sites from what are now 
Mississippi River Pools (MRP) 9 to 22 (Havlik 2001b, p. 10). Grier 
(1922, p. 11) did not find spectaclecase in sampled portions of MRP 4 
to 6. Van der Schalie and van der Schalie (1950, p. 456), reporting on 
studies from the upper Mississippi River to the Missouri River mouth, 
stated that no live spectaclecase were found in their study of 254 
sites during 1930-31. Havlik and Stansbery (1977, p. 12) thought the 
spectaclecase had disappeared from MRP 8 by the 1920s. Thiel (1981, p. 
10) found only shell material in MRP 11 in a survey that spanned MRP 3 
to 11 conducted during 1977 to 1980. Whitney et al. (1997, p. 12) 
recorded a single individual during 1994-1995 in MRP 15, for a density 
of 0.004 per square foot (sq. ft) (0.04 per square meter (sq. m)). 
Helms (2008, p. 8) found eight live individuals and numerous shells 
during a recent search of MRP 19, representing the most recent and 
numerous collection of the species in the Mississippi River.
    The spectaclecase is thought to be extant in at least four pools of 
the Mississippi River mainstem, albeit in very low numbers. Records 
include MRP 15 (Quad Cities area, Illinois and Iowa; in 1998), MRP 16 
(Muscatine area, Iowa and Illinois in 1997), MRP 19 (Burlington area, 
Illinois and Iowa in 2009), and MRP 22 (Quincy, Illinois and Hannibal, 
Missouri, area in 1996). Populations may still persist in MRP 9 and 10 
where specimens were found in the 1980s (Heath 2010a, pers. comm.). 
Only a relic spectaclecase shell was found in MRP 3 above the St. Croix 
River confluence in 2001, and none were found in subsequent surveys 
(Kelner 2008, pers. comm.). In general, spectaclecase population levels 
in the upper Mississippi River appear to have always been fairly small 
and difficult to locate, and are now of questionable long-term 
    St. Croix River: The northernmost and one of the three most 
significant extant populations of the spectaclecase occurs in the St. 
Croix River, Minnesota and Wisconsin. The population is primarily found 
in the middle reaches of the river in Chisago and Washington Counties, 
Minnesota, and Polk and St. Croix Counties, Wisconsin (river miles (RM) 
17 to 118). Havlik (1994, p. 19) reported spectaclecase in the St. 
Croix Wild River State Park portion of the river (approximately RM 62 
to 65) and the reproducing population below the St. Croix Falls Dam at 
St. Croix Falls, Wisconsin (dam located at approximately RM 52). 
Additional survey work in the lower river at Afton State Park 
(approximately RM 7 to 9) failed to find the spectaclecase (Havlik 
1994, p. 19).
    Hornbach (2001, p. 218) reported 68 live specimens from 4 of 16 
river reaches. Relative abundance for the spectaclecase varied from 
0.67 percent from RM 78 to 92 (20 live spectaclecase among 17 species 
collected), 0.008 percent from RM 63 to 78 (41 live, 24

[[Page 3398]]

species), 0.0006 percent from RM 42 to 52 (6 live, 33 species), and 
0.003 percent from RM 40 to 42 (1 live, 21 species). Reaches where the 
spectaclecase is extant are fragmented by the pool formed from the 
power dam at St. Croix Falls.
    Baird (2000, p. 70) presented a length-frequency histogram for the 
spectaclecase in the St. Croix River using data from an unpublished 
1989 study. The 962 specimens were fairly evenly distributed over the 
length scale, indicating multiple age classes including healthy numbers 
of young spectaclecase recruiting into the population. Baird (2000, p. 
70) used growth curves determined from his Missouri study of the 
species to estimate the ages of spectaclecase of known size in the St. 
Croix River. The percentage of newly recruited individuals (less than 
or equal to 10 years of age) in the St. Croix was 40 percent-- 
considerably higher than that noted from the Gasconade (10.4 percent) 
and Meramec (2.8 percent) Rivers in Missouri, two other streams with 
abundant spectaclecase populations that he studied. The St. Croix 
spectaclecase population, while among the largest known, may also be 
the healthiest based on this metric. The spectaclecase is currently 
distributed from RM 17 to 118 and appears to be recruiting from RM 17 
to 54 (downstream of the St. Croix Falls Dam) (Heath 2008, pers. 
    The long-term health of mussel populations in the St. Croix may be 
in jeopardy, however. Hornbach et al. (2001, pp. 12-13) determined that 
juvenile mussel density had suffered a statistically significant 
decline at three of four lower St. Croix sites sampled in the 1990s and 
in 2000. Zebra mussels also threaten the spectaclecase and other mussel 
populations in the lower St. Croix River. A 2000 survey at 20 sites on 
the lowermost 24 miles of the St. Croix River estimated that nearly one 
percent of the mussels were infested with zebra mussels (Kelner & Davis 
2002, p. 36).
    Meramec River: The Meramec River flows into the Mississippi River 
downstream of St. Louis in east-central Missouri. Its spectaclecase 
population represents one of the best remaining rangewide. In the late 
1970s, Buchanan (1980, p. 13) reported this species from 31 sites, 19 
with live individuals. Live or fresh dead individuals occurred from RM 
17.5 to 145.7. Buchanan (1980, p. 6) considered it to be common in the 
lower 108 miles (174 km) of the Meramec River, but locally abundant 
from RM 17.5 to 84. In 1997, Roberts and Bruenderman (2000, pp. 39, 
44), using similar sampling methods as Buchanan (1980, pp. 4-5), 
resurveyed the Meramec River system and collected spectaclecase from 23 
sites, 19 of which had live individuals. They found the largest 
populations between RM 56.7 and 118.8. Among 17 sites where 
spectaclecase were found during both surveys, the species was less 
abundant at nine sites and more abundant at five sites in 1997. At 
three sites, only relic shells were found during both surveys. In the 
1970s, Buchanan (1980, p. 10) reported finding 456 live individuals 
among the 17 shared sites, whereas Roberts and Bruenderman (2000, p. 
44) recorded only 198. A reduction in spectaclecase numbers (260 to 33) 
at RM 59.5 accounted for most of the overall decrease in abundance 
between the studies. Confounding the decrease in numbers among shared 
survey sites, Roberts and Bruenderman (2000, p. 44) surveyed three 
sites between RM 56.7 and 118.8 that were unsampled by Buchanan (1980, 
pp. 1-69) and found 500, 538, and 856 live spectaclecase. The most 
specimens found at a single site in the earlier study was 260 (RM 
59.5). Currently, the population in the Meramec River stretches over 
much of the mainstem, a distance of over 100 miles (161 km) from RM 
18.5 to 120.4.
    The spectaclecase represented 28 percent of all mussels sampled in 
the Meramec River in 1997 (Roberts & Bruenderman 2000, p. 39). Baird 
(2000, pp. 62, 68,77) extensively studied the demographics of the 
Meramec River spectaclecase population in the late 1990s. The mean 
estimated age of the population was 32 years. Individuals less than 10 
years of age comprised only 2.8 percent of the Meramec population 
sampled (a total of 2,983 individuals). At the four sites he 
intentionally selected for their large spectaclecase populations, 
densities ranged from 0.01 to 0.12 per sq. ft (0.1 to 1.3 per sq. m) 
while estimated population numbers at these sites ranged from 933 to 
22,697. Baird (2000, p. 71) thought that conditions for spectaclecase 
recruitment in the Meramec had declined in the past 20 to 30 years, but 
the causes were undetermined. The prevalence of larger adults in the 
Meramec population may be cause for concern, as it appears to indicate 
a low level of recruitment in the population.
    Bourbeuse River: The Bourbeuse River is a northern tributary of the 
Meramec River joining it at RM 68. Its spectaclecase population was 
sampled in 1997 at a single site (RM 10.3), and 7 live individuals were 
found (Roberts & Bruenderman 2000, p. 91). Sampling near the mouth (RM 
0.4), Buchanan (1980, p. 16) found only relic shells. The Bourbeuse 
population is probably dependent on the much larger Meramec population 
for long-term sustainability.
    Big River: Another Meramec tributary with a population of the 
spectaclecase, the Big River flows northward into the Meramec River at 
RM 38. The spectaclecase is only known from the lower end (RM 1.3), 
where 14 live specimens were found in 1997 (Roberts & Bruenderman 2000, 
p. 96). At RM 0.4, Buchanan (1980, p. 13) found only relic shells. 
Similar to the Bourbeuse River population, the population in the Big 
River is probably dependent on the much larger Meramec population for 
sustainability. The Meramec River system, including the lower 
Bourbeuse, lower Big, and Meramec River mainstems, can be considered a 
single spectaclecase population cluster.

Lower Missouri River System

    The spectaclecase was historically known from 10 streams in the 
Missouri River system. Currently, only four of these streams are 
thought to have extant populations.
    Sac River: The Sac River is a large tributary to the Osage River. 
The spectaclecase was considered extirpated in the 2002 status review 
of the species (Butler 2002a). However, three old, live individuals 
were collected at two sites during a survey of the Sac River in 2004 
(Hutson & Barnhart 2004, p. 17). The same survey revealed ``numerous'' 
relic shells from six other sites, indicating that the spectaclecase 
may have been relatively abundant at one time. Prior to the 2004 
survey, the spectaclecase had not been collected from this river since 
1978 (Bruenderman 2001, pers. comm.). Given the age of the live 
individuals and the abundance of shell material, Hutson & Barnhart 
(2004, p. 17) predicted the species would ``soon be extirpated'' from 
the river.
    Gasconade River: The Gasconade River is a southern tributary of the 
Missouri River in south-central Missouri and flows into the mainstem 
east of Jefferson City. When Stansbery (1970, p. 13) included this 
species in the first compiled list of imperiled mussels, he noted that 
``the only population of substantial size presently known is found in 
the Gasconade River.'' In 1994, Buchanan found over 1,000 individuals 
between RM 7 and 84 (Buchanan 1994, pp. 5, 8-13). Today, one of the 
three best spectaclecase populations remaining rangewide occurs in the 
Gasconade. The spectaclecase population occurs over approximately 200 
miles (322 km) of the mainstem from RM 4.9 upstream (Bruenderman et al. 
2001, p. 54). Baird (2000, pp. 61, 71) studied the demographics of the 
Gasconade River spectaclecase

[[Page 3399]]

population in the late 1990s. Based on his limited number of sampling 
sites, this species comprised about 20 percent of the entire mussel 
fauna in this system. The mean estimated age of the population was 25 
years. Individuals less than 10 years of age comprised 10.4 percent of 
the Gasconade population sampled (n = 2,111), indicating a significant 
level of recent recruitment.
    Historically, Stansbery (1967, p. 29) noted that ``[t]he size of 
some aggregation[s] * * * is impressive,'' and that ``the number of 
individuals may reach a density of well over a dozen per square foot.'' 
Both statements are probably in reference to the Gasconade River, 
Missouri, population, which he had described in the text of his note. 
Densities at the four sites Baird (2000, pp. 61, 71) intentionally 
selected for their large spectaclecase populations ranged from 0.03 to 
0.06 per sq. ft (0.3 to 0.6 per sq. m); estimated population numbers at 
these selected sites ranged from 2,156 to 4,766. Baird (2000, p. 71) 
thought that conditions for spectaclecase recruitment in the Gasconade 
River had declined in the past 20 to 30 years, but the causes were 
    Big Piney River: The Big Piney River, a southern tributary of the 
Gasconade River, harbors a small population of the spectaclecase. 
Although overlooked during a 1999 survey (Bruenderman et al. 2001, pp. 
14, 28), 15 individuals were collected from the lower mainstem (RM 24) 
in 2004 (Barnhart et al. 2004, p. 5). The status of the population is 
unknown, but it is probably dependent on the much larger source 
population in the Gasconade River for sustainability (McMurray 2008, 
pers. comm.).
    Osage Fork: The Osage Fork is a southwestern headwater tributary of 
the Gasconade River. The spectaclecase is known from the lower portion 
of this Gasconade River tributary, specifically from RM 13.9. Sampling 
in the Osage Fork in 1999 yielded 26 live individuals from this site 
(Bruenderman et al. 2001, p. 9). Relative abundance of the 
spectaclecase in the Osage Fork was 3.9 percent, and catch-per-unit 
effort was 1.3 per person-hour. This population is thought to be 
stable, but it may also be dependent on the much larger source 
population in the Gasconade River for long-term sustainability. The 
Gasconade River system, including the lower Big Piney, lower Osage 
Fork, and Gasconade mainstems, can be considered a single population 

Ohio River System

    The spectaclecase's continued existence in the Ohio River is 
extremely uncertain. Once known from five rivers, it has been 
extirpated from two, and two of the remaining three are recently 
represented by only one or two individuals each.
    Ohio River: The Ohio River is the largest eastern tributary of the 
Mississippi River, with its confluence marking the divide between the 
upper and lower portions of the Mississippi River system. Historically, 
the spectaclecase was documented from the Ohio River from the vicinity 
of Cincinnati, Ohio, to its mouth. Although no specimens are known from 
the mainstem upstream of Cincinnati, populations are known from two 
upstream tributaries, the Muskingum and Kanawha Rivers. Nearly all 
spectaclecase records from the Ohio River were made around 1900 or 
before (Schuster 1988, p. 186). The only recent record is for a single 
live individual found in an abandoned gill net near the Illinois shore 
in 1994 (Cummings 2008, pers. comm.). If a population of the 
spectaclecase continues to occur in the Ohio River, its future 
persistence is extremely doubtful and continued existence seriously 
threatened by the exotic zebra mussel.
    Kanawha River: The Kanawha River is a major southern tributary of 
the Ohio River that drains much of West Virginia. The spectaclecase was 
not known from this stream until 2002, when a single, very old, live 
individual was discovered near Glasgow, Kanawha County (Zimmerman 2002, 
pers. comm.). Another live individual was found in the same vicinity in 
2005, as well as two additional weathered shells in 2006 (Clayton 
2008a, pers. comm.). This site is approximately 20 miles (32.2 km) 
downstream of Kanawha Falls, below which is the only significant mussel 
bed known from the Kanawha River. It is doubtful that a recruiting 
spectaclecase population occurs in the Kanawha River due to the small 
number of individuals found and their advanced age.
    Green River: The Green River is a lower Ohio River tributary in 
west-central Kentucky. The spectaclecase has been collected sparingly 
in the Green River. That it was not reported in early collections made 
in the system is indicative of the difficulty in finding specimens 
(Price 1900, pp. 75-79). Stansbery (1965, p. 13) was the first to find 
it in the mid-1960s at Munfordville, Hart County, where he reported 47 
mussel species collected over a several-year period in the early 1960s. 
More recently, from 1987 to 1989, Cicerello and Hannan (1990, p. 20) 
reported single fresh dead specimens at six sites and relic specimens 
from an additional five sites in Mammoth Cave National Park (MCNP). A 
single specimen was recorded from MCNP, Edmonson County, in 1995. 
Sampling conducted from 1996 to 1998 located fresh dead specimens at 
two sites above MCNP, with a relic shell at a third site farther 
upstream (Cicerello 1999, pp. 17-18). At least one fresh dead specimen 
was reported from MCNP in 2001, as well as several live individuals in 
2005 and 2006 (Layzer 2008, pers. comm.).
    A small spectaclecase population remains in the upper Green River 
from below Lock and Dam 5 upstream through MCNP, Edmonson County, into 
western Hart County. Most recent specimens have been reported from the 
upstream portion of this reach, where it is generally distributed from 
MCNP upstream to western Hart County. Its distribution is much more 
sporadic and localized in the lower portion of this reach due to the 
pooling effect of two locks and dams (5 and 6). In 2001, a concerted 
effort (approximately 15 person-hours) to locate rare mussels below 
Lock and Dam 5 and at other sites downstream failed to find 
spectaclecase (live or shell), although a fresh dead shell had been 
collected in this area in 1993 (Cicerello 2008, pers. comm.). The 
occurrence of variable-sized individuals in the 1990s indicates 
different year classes but not necessarily recent recruitment 
(Cicerello 2008, pers. comm.). The long-term sustainability of the 
Green River population, primarily limited to an approximately 15-mile 
(24-km) reach of the river, is therefore questionable, and its status 
is unknown.

Cumberland River System

    With few exceptions, most records of the spectaclecase in the 
Cumberland River system were made before the 1920s. It was historically 
known from the mainstem and four tributaries but appears currently to 
be restricted to the lowermost Cumberland River a few miles above its 
confluence with the Ohio River.
    Cumberland River mainstem: The Cumberland River is a large southern 
tributary of the lower Ohio River. The spectaclecase was considered 
``not rare'' in the Cumberland River by Hinkley and Marsh (1885, p. 6), 
whereas it was found at six sites by Wilson and Clark (1914, pp. 17, 
19) during their survey primarily for commercial species in the 
Cumberland River system. In a 1947-1949 survey of the Kentucky portion 
of the upper Cumberland River, Neel and Allen (1964, p. 453) reported 
live specimens only from one of six mainstem sites that they sampled 
below Cumberland Falls. Neel and Allen (1964, p. 432) considered it to 
be ``uncommon'' in the lower Cumberland River (where they did not 
sample), a

[[Page 3400]]

statement possibly based on its sporadic occurrence as reported by 
Wilson and Clark (1914, pp. 17, 19). One of the last mainstem records 
is that of a single live specimen found in the cold tailwaters of Wolf 
Creek Dam, Kentucky, near the Tennessee border in 1982 (Miller et al. 
1984, p. 108). This was one of only two live mussels found during a 
survey of the dewatered river reach below the dam, the mussel community 
having been eliminated from decades of cold water releases. The most 
recent record is of a single live individual found at RM 10 below 
Barkley Lock and Dam in 2008 (Fortenbery 2008, p. 9). A thorough search 
of the area yielded no additional individuals.

Tennessee River System

    The spectaclecase was originally known from the Tennessee River and 
nine of its stream systems. Ortmann (1924, p. 60) reported that the 
spectaclecase was ``frequent[hellip] in the upper Tennessee,'' while 
acknowledging in an earlier paper (Ortmann 1918, p. 527) that it was 
locally abundant in parts of the upper Tennessee River system, but 
noted that it was ``generally regarded as a rare species'' rangewide.
    Hundreds of miles of large river habitat on the Tennessee mainstem 
have been converted under nine reservoirs, with additional dams 
constructed in tributaries historically harboring this species (for 
example, Clinch, Holston, and Elk Rivers). Watters (2000, p. 262) 
summarizes the tremendous loss of mussel species from various reaches 
of the Tennessee. The spectaclecase is now known only from the 
Tennessee mainstem and three of its tributaries. Despite this fact, the 
Tennessee River system continues to represent one of the last 
strongholds of the spectaclecase rangewide.
    Tennessee River mainstem: The Tennessee River is the largest 
tributary of the Ohio River, draining portions of seven states. The 53-
mile (85-km) stretch of river in northwestern Alabama collectively 
referred to as the Muscle Shoals historically harbored 69 species of 
mussels, making it among the most diverse mussel faunas ever known 
(Garner & McGregor 2001, p. 155). The historical spectaclecase 
population in this reach was thought to be phenomenal given the amount 
of historical habitat that was available and literature accounts of the 
period. Hinkley (1906, p. 54), in 1904, considered the spectaclecase 
``plentiful,'' noting 200 individuals under a single slab boulder. 
Twenty years later, Ortmann (1925, p. 327) stated that ``this species 
must be, or have been, abundant'' at Muscle Shoals based on the 
``considerable number of dead shells'' he observed. In these quotes he 
predicted the demise of the spectaclecase. The construction of three 
dams (Wilson in 1925, Wheeler in 1930, Pickwick Landing in 1940) 
inundated most of the historical habitat, leaving only small habitat 
remnants (Garner & McGregor 2001, p. 155). The largest remnant habitat 
remaining is the Wilson Dam tailwaters, a reach adjacent to and 
downstream from Florence, Alabama.
    With the exception of 1976-1978 when it was ``collected 
infrequently'' from below Wilson Dam (Gooch et al. 1979, p. 90), no 
collections of the spectaclecase were reported at Muscle Shoals from 
1931 to 1995 despite surveys conducted in 1956-1957, 1963-1964, and 
1991 (Garner & McGregor 2001, p. 156).
    Elsewhere along the Tennessee mainstem, a specimen was recently 
reported from the Guntersville Dam tailwaters in northern Alabama 
(Butler 2002a, p. 17). From 1997-1999, 10 live, 1 fresh dead, and 4 
relic spectaclecase were reported from three sites in this river reach 
based on Ohio State University Museum (OSUM) records. The species is 
found only occasionally in the lower Tennessee River below Pickwick 
Landing Dam in southeastern Tennessee, having been unreported in 
various surveys (for example, Scruggs 1960, p. 12; van der Schalie 
1939, p. 456). Yokley (1972, p. 61) considered it rare, having only 
found fresh dead specimens in his 3-year study. Hubbs and Jones (2000, 
p. 28) reported two live specimens found in 1998 at RM 170, Hardin 
County. The current status of these small populations is unknown 
(Garner 2008, pers. comm.; Hubbs 2008, pers. comm.).
    Clinch River: The Clinch River is a major tributary of the upper 
Tennessee River in southwestern Virginia and northeastern Tennessee. 
B[ouml]pple and Coker (1912, p. 9) noted numerous spectaclecase shells 
in muskrat middens in a portion of the Clinch that is now inundated by 
Norris Reservoir. Ortmann (1918, p. 527) reported the spectaclecase as 
being locally abundant in the lower Clinch River, again in an area 
mostly flooded by Norris Reservoir. Oddly, he failed to find this 
species upstream of Claiborne County, yet, in later years, one of the 
spectaclecase's largest known populations was identified in this reach. 
The species was locally common at sites in the upper Clinch River, 
according to OSUM records from the 1960s. Ahlstedt (1991a, p. 98) 
considered this species to be relatively rare in the Clinch River based 
on survey work conducted during 1978 to 1983. He recorded 78 live 
specimens from 22 sites between RM 151 and 223, for an average of 3.5 
per site. The spectaclecase population reported by Ahlstedt (1991a, pp. 
89-90) from the lower Clinch River between Melton Hill and Norris Dam 
(11 specimens from 4 sites between RM 45 and 73) was considered to be 
small but stable. Once considered abundant in the Clinch River at 
Speers Ferry, Scott County, Virginia (Bates & Dennis 1978, pp. 18-19), 
the species is now extremely rare at this site (Neves 1991, p. 264).
    Currently, the species is locally common in the Tennessee River 
system only in the upper Clinch River, and populations are primarily 
restricted to the Tennessee portion of that stream. Despite low numbers 
(0.02 per sq. ft (0.2 per sq. m)) detected in quantitative sampling 
(428; 2.7 sq. ft (0.25 sq. m) quadrats) in 1994 (Ahlstedt & Tuberville 
1997, pp. 73, 81), the upper Clinch River in Tennessee may still yield 
two to three dozen specimens under individual slab boulders. Three 
individuals were collected at RM 223.6 in Virginia in 2005, and one old 
individual was collected in 2007 at RM 270.8, representing the farthest 
upstream record for the species (Eckert 2008, pers. comm.). The upper 
Clinch River population is considered to be reproducing, with fairly 
young individuals occasionally found, but overall the population 
appears to be declining (Ahlstedt 2008, pers. comm.). The recent 
occurrence of a disjunct population in the lower Clinch River 
(separated from the upper Clinch River population by Norris Reservoir) 
was recently verified (Fraley 2008, pers. comm.). The specimens sampled 
likely recruited since the Norris Dam gates closed in 1936 (Fraley 
2008, pers. comm.), despite the cold tailwaters that destroyed the 
majority of the mussel fauna in this once incredibly diverse river 
    Nolichucky River: The Nolichucky River is a tributary of the lower 
French Broad River, in the upper Tennessee River system in North 
Carolina and Tennessee. The spectaclecase population in this river was 
once sizable, judging from museum lots (for example, 23 fresh dead, 
OSUM 1971:0372). Sampling at 41 Nolichucky River sites in 1980, 
Ahlstedt (1991b, pp. 136-137) reported 8 live spectaclecase from 6 
sites between RM 11.4 to 31.9. A small population of the spectaclecase 
also persists in a relatively short reach of the lower river (Ahlstedt 
2008, pers. comm.). The current status of the Nolichucky River 
population is unknown.
    Duck River: The Duck River is wholly in Tennessee and represents 
the farthest downstream significant tributary of the

[[Page 3401]]

Tennessee River, joining it in the headwaters of Kentucky Reservoir. A 
single spectaclecase, representing a new drainage record, was found 
live in lower Duck River, Hickman County, in 1999 (Hubbs 1999, p. 1; 
Powell 2008, pers. comm.). Since then, at least two individuals from 
the lower part of the river in Humphreys County have been documented, 
and several relic specimens have been reported farther upstream (Hubbs 
2008, pers. comm.; Powell 2008, pers. comm.). These records cover an 
approximately 20-mile (32-km) reach of river, with the live individual 
reported from the lower end of this reach. The spectaclecase is 
considered extremely rare in the Duck River, and its status is unknown.

Lower Mississippi River System

    The spectaclecase was apparently never widely distributed in the 
lower Mississippi River system. Records from only two streams are 
known, both from Arkansas.
    Mulberry River: The Mulberry River is a tributary of the Arkansas 
River in northwestern Arkansas. Other than the Ouachita River records, 
the only other record of the spectaclecase in the lower Mississippi 
River system is a single specimen found in the mid-1990s in the 
Mulberry River. There is some uncertainty regarding the validity of 
this record, as the collectors were not experienced malacologists, and 
no specimen or photograph is available to substantiate the record. This 
record is, however, accepted as valid (Harris et al. 2009, p. 67; 
Harris 2010, pers. comm.). The status of the spectaclecase in the 
Mulberry River is unknown.
    Ouachita River: The Ouachita River flows into lower Red River, a 
major western tributary of the lower Mississippi River, draining 
portions of Arkansas and Louisiana. This species was first reported in 
this portion of its range from the Ouachita River, southwestern 
Arkansas, in the early 1900s (Wheeler 1918, p. 121). Spectaclecase 
records in the Ouachita span a three-county reach of river. Only two 
live specimens were found in the mid-1990s, both in the lower portion 
of Ouachita County. A single relic shell (paired valves) was found in 
Montgomery County, at the upper end of its Ouachita River range in 
2000. The population is considered very small and declining (Harris et 
al. 2009, p. 67; Harris 2010).

Summary of Extant Spectaclecase Populations

    The spectaclecase appears to be declining rangewide, with the 
exception of a few significant populations. Its occurrence in the St. 
Croix, Meramec, Gasconade, and Clinch Rivers represent the only 
sizable, sustainable, and reproducing populations remaining, although 
the Clinch River population appears to be in decline. The spectaclecase 
has been eliminated from three-fifths of the total number of streams 
from which it was historically known (19 streams currently compared to 
44 streams historically). This species has also been eliminated from 
long reaches of former habitat in thousands of miles of the Illinois, 
Ohio, Cumberland, and other rivers, and from long reaches of the 
Mississippi and Tennessee Rivers. In addition, the species is no longer 
known from the States of Ohio, Indiana, Kansas, and Nebraska. The 
extirpation of this species from numerous streams and stream reaches 
within its historical range signifies that substantial population 
losses have occurred.

Sheepnose Historical Range and Distribution

    Historically, the sheepnose occurred in the Mississippi, Ohio, 
Cumberland, and Tennessee River systems and their tributaries, totaling 
at least 77 streams (including 1 canal) (Butler 2002b). Its 
distribution comprised portions of 14 States (Alabama, Illinois, 
Indiana, Iowa, Kentucky, Minnesota, Mississippi, Missouri, Ohio, 
Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin). 
Historical occurrence by stream system (with tributaries) include the 
     Upper Mississippi River system (Mississippi River 
(Minnesota, St. Croix, Chippewa (Flambeau River), Wisconsin, Rock, 
Iowa, Des Moines, Illinois (Des Plaines, Kankakee, Fox, Mackinaw, 
Spoon, Sangamon (Salt Creek) Rivers; Quiver Creek; Illinois and 
Michigan Canal), Meramec (Bourbeuse, Big Rivers), Kaskaskia, Saline, 
Castor, Whitewater Rivers));
     Lower Missouri River system (Little Sioux, Little Blue, 
Gasconade (Osage Fork) Rivers);
     Ohio River system (Ohio River (Allegheny (Hemlock Creek), 
Monongahela, Beaver (Duck Creek), Muskingum (Tuscarawas, Walhonding 
(Mohican River), Otter Fork Licking Rivers), Kanawha, Scioto, Little 
Miami, Licking, Kentucky, Salt, Green (Barren River), Wabash 
(Mississinewa, Eel, Tippecanoe, Vermillion, Embarras, White (East, West 
Forks White River) Rivers) Rivers);
     Cumberland River system (Cumberland River (Obey, Harpeth 
Rivers; Caney Fork));
     Tennessee River system (Tennessee River (Holston (North 
Fork Holston River), French Broad (Little Pigeon River), Little 
Tennessee, Clinch (North Fork Clinch, Powell Rivers), Hiwassee, Duck 
Rivers)); and
     Lower Mississippi River system (Hatchie, Black, Yazoo (Big 
Sunflower River), Big Black Rivers).

Sheepnose Current Range and Distribution

    Extant populations of the sheepnose are known from 24 rivers in all 
14 States of historical occurrence. Current populations occur in the 
following systems (with tributaries):
     Upper Mississippi River system (Mississippi River 
(Chippewa (Flambeau River), Wisconsin, Kankakee, Meramec (Bourbeuse 
River) Rivers));
     Lower Missouri River system (Osage Fork, Gasconade River); 
Ohio River system (Ohio River (Allegheny, Muskingum (Walhonding River), 
Kanawha, Licking, Kentucky, Tippecanoe, Eel, Green Rivers));
     Tennessee River system (Tennessee River (Holston, Clinch, 
Duck (Powell River) Rivers)); and
     Lower Mississippi River system (Big Sunflower River).
    The 24 extant sheepnose populations occur in the following 14 
States (with streams):
     Alabama (Tennessee River),
     Illinois (Mississippi, Kankakee, Ohio, Wabash Rivers),
     Indiana (Ohio, Tippecanoe, Eel Rivers),
     Iowa (Mississippi River),
     Kentucky (Ohio, Licking, Kentucky, Green Rivers),
     Minnesota (Mississippi River),
     Mississippi (Big Sunflower River),
     Missouri (Mississippi, Meramec, Bourbeuse, Osage Fork 
Gasconade Rivers),
     Ohio (Ohio, Muskingum Rivers),
     Pennsylvania (Allegheny River),
     Tennessee (Tennessee, Holston, Clinch, Powell, Duck 
     Virginia (Clinch, Powell Rivers),
     West Virginia (Ohio, Kanawha Rivers), and
     Wisconsin (Mississippi, St. Croix, Chippewa, Flambeau, 
Wisconsin Rivers).
    The sheepnose was last observed from over two dozen streams decades 
ago (e.g., Minnesota, Rock, Iowa, Illinois, Des Plaines, Fox, Mackinaw, 
Spoon, Castor, Little Sioux, Little Blue, Monongahela, Beaver, Scioto, 
Little Miami, Salt, Mississenewa, Vermilion, Embarras, White, Obey, 
Harpeth, North Fork Holston, French Broad, North Fork Clinch Rivers; 
Caney Fork). According to Parmalee and Bogan (1998, p. 177) and Neves 
(1991, pp. 280-281), the sheepnose has been extirpated

[[Page 3402]]

throughout much of its former range or reduced to isolated populations. 
The only records known from some streams are archeological specimens 
(for example, Little Pigeon, Big Black, Yazoo Rivers; Saline River).

Sheepnose Population Estimates and Status

    The sheepnose has been eliminated from two-thirds of the total 
number of streams from which it was historically known (24 streams 
currently occupied compared to 77 streams historically) (Table 2). This 
species has also been eliminated from long reaches of former habitat 
including thousands of miles of the Mississippi, Wisconsin, Illinois, 
Ohio, Cumberland, and Tennessee Rivers and dozens of other streams and 
stream reaches.
    Based on the population designation criteria (see Species 
Distribution section, above), of the 24 sheepnose populations that are 
considered extant, 11 are thought to be stable and 8 are considered 
declining (Table 2). Five other populations (Walhonding, Gasconade, 
Muskingum, Osage Fork, and Duck Rivers) are considered extant, but the 
status of these populations is unknown.

                                Table 2--Sheepnose Status at Historical Locations
                                                                             Date of last
           River basin                  Stream          Current status        observation          Comments
Upper Mississippi River.........  Mississippi River.  Declining.........  2008..............  ..................
                                  Minnesota River...  Extirpated........  ~1944.............  ..................
                                  St. Croix River...  Extirpated........  1988..............  ..................
                                  Chippewa/Flambeau   Stable............  ~1994.............  ..................
                                  Wisconsin River...  Declining.........  2002..............  ..................
                                  Rock River........  Extirpated........  1926..............  ..................
                                  Iowa River........  Extirpated........  1925..............  Relic shell
                                                                                               collected in
                                  Des Moines River..  Extirpated........  ~1915.............  ..................
                                  Illinois River....  Extirpated........  1940..............  Relic shell
                                                                                               collected in
                                  Des Plaines River.  Extirpated........  ~1970.............  ..................
                                  Kankakee River....  Stable............  2007..............  ..................
                                  Fox River.........  Extirpated........  ~1913.............  ..................
                                  Mackinaw River....  Extirpated........  ~1970.............  ..................
                                  Spoon River.......  Extirpated........  1929..............  ..................
                                  Sangamon River....  Extirpated........  ~1919.............  Relic shell
                                                                                               collected in
                                  Salt Creek........  Extirpated........  Unknown...........  Relic shell
                                                                                               collected in
                                  Quiver Creek......  Extirpated........  1881..............  ..................
                                  Illinois and        Extirpated........  ?.................  ..................
                                   Michigan (I & M)
                                  Meramec River.....  Stable............  2002..............  ..................
                                  Bourbeuse River...  Declining.........  1997..............  ..................
                                  Big River.........  Extirpated........  1978..............  ..................
                                  Kaskaskia River...  Extirpated........  1970..............  ..................
                                  Saline River......  Extirpated........  ?.................  ..................
                                  Castor River......  Extirpated........  ~1965.............  ..................
                                  Whitewater River..  Extirpated........  1970s.............  ..................
Lower Missouri River............  Little Sioux River  Extirpated........  1916..............  ..................
                                  Little Blue River.  Extirpated........  ~1915.............  ..................
                                  Gasconade River...  Unknown...........  ~1965.............  ..................
                                  Osage Fork........  Unknown...........  1999..............  Represented by
                                                                                               single specimen,
                                                                                               presumably near
Ohio River......................  Ohio River........  Stable............  2007..............  ..................
                                  Allegheny River...  Improving.........  2008..............  ..................
                                  Hemlock Creek.....  Extirpated........  Unknown...........  Relic shell
                                                                                               collected in
                                  Monongahela River.  Extirpated........  ~1897.............  ..................
                                  Beaver River......  Extirpated........  ~1910.............  ..................
                                  Duck Creek........  Extirpated........  1930..............  ..................
                                  Muskingum River...  Unknown...........  1993..............  ..................
                                  Tuscarawas River..  Extirpated........  Unknown...........  Relic shell
                                                                                               collected in
                                  Walhonding River..  Unknown...........  1993..............  ..................
                                  Mohican River.....  Extirpated........  1977..............  ..................
                                  Otter Fork Licking  Extirpated........  1973..............  ..................
                                  Kanawha River.....  Stable............  2005..............  ..................
                                  Scioto River......  Extirpated........  1963..............  ..................
                                  Little Miami River  Extirpated........  ~1953.............  ..................
                                  Licking River.....  Declining.........  1998..............  ..................
                                  Kentucky River....  Declining.........  1996..............  ..................
                                  Salt River........  Extirpated........  ~1900.............  ..................
                                  Green River.......  Improving.........  2007..............  ..................
                                  Barren River......  Extirpated........  Unknown...........  Relic shell
                                                                                               collected in
                                  Wabash River......  Extirpated........  1988..............  ..................
                                  Mississinewa River  Extirpated........  1899..............  ..................
                                  Eel River.........  Declining.........  1997..............  ..................
                                  Tippecanoe River..  Stable............  1995..............  ..................
                                  Vermillion River..  Extirpated........  Unknown...........  ..................
                                  Embarras River....  Extirpated........  1953..............  ..................
                                  White River.......  Extirpated........  1913..............  ..................
                                  East White River..  Extirpated........  1969..............  ..................

[[Page 3403]]

                                  West Fork White     Extirpated........  1908..............  Relic shell
                                   River.                                                      collected in
Cumberland River................  Cumberland River..  Extirpated........  1987..............  ..................
                                  Obey River........  Extirpated........  1939..............  ..................
                                  Harpeth River.....  Extirpated........  ?.................  ..................
                                  Caney Fork River..  Extirpated........  Unknown...........  Relic shell
                                                                                               collected in
Tennessee River.................  Tennessee River...  Stable............  2004..............  ..................
                                  Holston River.....  Declining.........  2007..............  ..................
                                  North Fork Holston  Extirpated........  1913..............  ..................
                                  French Broad River  Extirpated........  1914..............  ..................
                                  Little Pigeon       Extirpated........  Unknown...........  ..................
                                  Little Tennessee    Extirpated........  Unknown...........  Relic shell
                                   River.                                                      collected in
                                  Clinch River......  Stable............  2006..............  ..................
                                  North Fork Clinch   Extirpated........  ~1921.............  ..................
                                  Powell River......  Stable............  2004..............  ..................
                                  Hiwassee..........  Extirpated........  Unknown...........  Relic shell
                                                                                               collected in
                                  Duck River........  Unknown...........  2003..............  Record represented
                                                                                               by single
Lower Mississippi River.........  Hatchie River.....  Extirpated........  1983..............  ..................
                                  Black River.......  Extirpated........  Unknown...........  ..................
                                  Yazoo River.......  Extirpated........  Unknown...........  ..................
                                  Big Sunflower       Declining.........  2000..............  ..................
                                  Big Black River...  Extirpated........  Unknown...........  ..................

    Historically, the sheepnose was fairly widespread in many 
Mississippi River system streams, although rarely common. 
Archaeological evidence on relative abundance indicates that it has 
been an uncommon or even rare species in many streams for centuries 
(Morrison 1942, p. 357; Patch 1976, pp. 44-52; Parmalee et al. 1980, p. 
101; Parmalee et al. 1982, p. 82; Parmalee and Bogan 1986, pp. 28, 30; 
Parmalee and Hughes 1994, pp. 25-26), and relatively common in only a 
few (Bogan 1990, p. 135).
    Museum collections of this species are almost always few in number 
(Cummings 2010, pers. comm.), with the exception of the 1960s 
collections from the Clinch and Powell Rivers, Tennessee and Virginia. 
Moderate numbers of individuals were also commonly recorded 
historically from the upper Muskingum River system in Ohio and the 
lower Wabash River in Indiana and Ohio, based on museum lots. Schuster 
and Williams (1989, p. 21) reported the species as being not common in 
the Ohio River, while Cummings and Mayer (1992, p. 50) considered it 
rare throughout its range. The American Malacological Union considers 
the sheepnose to be threatened (Williams et al. 1993, p. 13).
    Some known populations of the sheepnose are represented by the 
collection of a single specimen. Other populations have seen a dramatic 
range decline (for example, reduced from several hundred river miles to 
a single bed of a river system) or we have limited recent information 
on population status. The following summaries focus primarily on those 
populations for which we have sufficient information to make status and 
trend determinations, and less on those populations that are nearly 
extirpated, have no recruitment, or are of unknown status.

Upper Mississippi River System

    Judging from the archeological record, the sheepnose may have been 
common at some sites on the Mississippi River (Bogan 1990, p. 135) but 
over the past century it has become a rare species throughout the 
mainstem (Grier 1922, pp. 13-31; van der Schalie and van der Schalie 
1950, pp. 454-457). Robust populations may have been found in some 
tributary rivers. The sheepnose has been extirpated from eight 
Mississippi River tributaries (Minnesota, Rock, Iowa, Des Moines, 
Kaskaskia, Saline, Castor, and Whitewater Rivers) and all but one 
Illinois River tributary (the Kankakee River). Today, the sheepnose is 
extant (though in low numbers) in ten mainstem pools, and six tributary 
rivers of the Upper Mississippi River System.
    Mississippi River mainstem: Sheepnose populations in the mainstem 
of the Upper Mississippi River are declining. Despite the discovery of 
a juvenile in Mississippi River Pool (MRP) 7 in 2001, recruitment is 
limited at best. The mainstem population is comprised of a few old 
individuals spread across a very large geographic range (MRP 3 through 
MRP 24 a distance of over 550 river miles (880 river km)) (Thiel 1981, 
p. 10; Havlik and Marking 1981, p. 32; Whitney et al. 1996, p. 17; 
Helms and Associates, Ecological Specialists Inc. 2008, p. 16). The 
status of this species in the Mississippi River is highly jeopardized 
(Butler 2002b, p. 7).
    Pools with extant populations include MRP 3 (last seen live or 
fresh dead in 2000-01), MRP 4 (2008), MRP 7 (2001), MRP 11 (2007), MRP 
14 (2006-07), MRP 15 (2005-06), MRP 16 (2003), MRP 17 (2004), MRP 20 
(1992), and MRP 24 (1999). The 2001 MRP 7 record was for a live 
juvenile 1.3 inches (3.3 cm) long and estimated to be 3 years old 
(Davis 2008, pers. comm.).
    St. Croix River: The St. Croix River population is isolated and 
comprised of old individuals with little to no recruitment (Heath 
2010b, pers. comm.). Currently, the population is thought to be 
restricted to the lowermost mainstem below RM 1 in Washington County, 
Minnesota, and Pierce County, Wisconsin (Heath 2010b, pers. comm.). 
Three live individuals were collected in 1988, during a mussel 
relocation project for the U.S. Highway 10 bridge immediately upstream 
of the confluence with the Mississippi River (Heath 1989, p. 16). 
Hornbach (2001, p. 218) analyzed mussel collections throughout the St. 
Croix River and found that the sheepnose was absent in 15 of the 16 
river reaches he sampled, only noting the 1988 occurrence. One 
historical occurrence is known from the vicinity of RM 53 in 1930; 
however, this is the only known record upstream of RM 1 (Heath 2010b, 
pers. comm.). Because

[[Page 3404]]

there have been no recent collections in the St. Croix River since 
1988, this population is most likely extirpated.
    Chippewa/Flambeau River: The sheepnose population in the Chippewa 
River is extant in much of the river system including the lower end of 
its tributary, the Flambeau River. This population is stable with 
documented recruitment (Butler 2002b, p. 8). Balding and Balding (1996, 
p. 5) reported 50 live specimens sampled from 1989-1994, but more 
recent collections have expanded sites of occurrence to 20 of 67 sites 
in the middle and upper portions of the Chippewa River, with a relative 
abundance of 0.8 percent (Balding 2001, pers. comm.). Balding (1992, p. 
166) found 12 live specimens and 31 dead shells from 5 of 37 sites in 
the lower river. Additional survey work extended the number of sites 
where it was found live to 10 of 45 (Balding 2001, pers. comm.). The 
Flambeau River supports a small sheepnose population below its lowest 
dam and near its confluence with the Chippewa River (lower 8 miles (13 
km) of river), and is most likely dependent on the source population in 
the Chippewa River. The Chippewa River sheepnose population is 
considered one of the best known extant populations. The Flambeau River 
supports a small sheepnose population below its lowest dam and near its 
confluence with the Chippewa River (lower 8 miles (13 km) of river), 
and is most likely dependent on the source population in the Chippewa 
    Wisconsin River: The sheepnose is declining in the Wisconsin River. 
Historical records for the sheepnose are available throughout the lower 
335 miles (539 km) of the 420-mile (676-km) Wisconsin River (Heath 
2010c, pers. comm.). In July 2002, 20 live specimens were found in a 
dense mussel bed near Port Andrew (Seitman 2008, pers. comm.). 
Currently, the sheepnose is primarily confined to RM 133.7 downstream 
(a reduction of over 201 river miles (232 km)). The sheepnose 
population is probably recruiting in the river, primarily in the lower 
section (below RM 82) (Heath 2010b, pers. comm.). It is unknown if the 
middle river population, from RM 93 to 133.7, is recruiting because 
only three living individuals have been found in recent years (Heath 
2010c, pers. comm.).
    Kankakee River: The sheepnose once occurred along the lower two-
thirds of the Kankakee River, an Upper Illinois River tributary, in 
Indiana and Illinois (Wilson and Clark 1912, p. 47; Lewis and Brice 
1980, p. 4). The sheepnose has been extirpated from the channelized 
portion of the Kankakee in Indiana but persists in the Illinois portion 
of the river where it appears stable, with evidence of recent 
recruitment (Butler 2002b, p. 9). Records since 1986 identify the 
sheepnose in the Kankakee River from the Iroquois River confluence 
downstream approximately 30 river miles (48 km) (Cummings 2010, pers. 
comm.; Helms and Associates 2005, p. 3). A mussel relocation effort for 
a pipeline crossing in the Kankakee River in July 2002 found 11 
sheepnose individuals, representing 0.32 percent of the total mussels 
relocated (Helms 2004, p. D-1). Subsequent monitoring of the site in 
2004 and 2007 located four new individuals. One individual collected in 
2004 measured 1.6 inches (40 mm) and was estimated to be a juvenile of 
3 years of age.
    Meramec River: The Meramec River flows into the Mississippi River 
downstream of St. Louis and drains east-central Missouri. The Meramec 
sheepnose population is stable and recruiting, and represents one of 
the best rangewide (Butler 2002b, p. 9). Two studies (Buchanan 1980, p. 
4; Roberts & Bruenderman 2000, p. 20) extensively surveyed the mussel 
fauna of the Meramec River. The most notable difference in the results 
of these studies was the reduced range in which sheepnose were found. 
Buchanan (1980, p. 34) found live or fresh dead individuals from RM 4.5 
to 145.7 (141.2 river miles (227.2 km)), whereas Roberts and 
Bruenderman (2000, p. 20) found live or fresh dead individuals from RM 
25.6 to 91.3 (65.7 river miles (105.7 km)). The trend data from the 
late 1970s to 1997 indicate that the sheepnose declined 75.5 river 
miles (121.5 km) in total range within the Meramec River. The extent of 
the population in the lower end appears to be shrinking upriver (Butler 
2002b, p. 10).
    In 2002, a site associated with a railroad crossing in St. Louis 
County at RM 28 yielded 43 live specimens over 3 days of sampling, 
including at least one gravid female (Roberts 2008, pers. comm.). 
Collectively, these data reinforce the level of importance of the 
Meramec population for the sheepnose rangewide. Although the existing 
population has been described as stable and recruitment has been 
documented in the system (Butler 2002b, pp. 11-12), the population has 
shrunk by half of its former geographic range over the past 30 years.
    Bourbeuse River: The Bourbeuse River sheepnose population is 
distributed in the downstream 90 river miles (145 km) of the river 
(Buchanan 1980, p. 34), but is considered rare. Although recruitment 
has been documented in the Bourbeuse River, the sheepnose population is 
considered declining (Roberts and Bruenderman 2000, p. 130; Roberts 
2010, pers. comm.). In the late 1970s, Buchanan (1980, p. 10) found the 
sheepnose to represent 0.1 percent of the Bourbeuse River mussel fauna, 
with 10 live specimens sampled from 7 sites. Based on data collected by 
Buchanan (1980, p. 34) and additional survey work in 1980, live or 
fresh-dead individuals were found in the Bourbeuse from RM 6.5 to 90.0. 
Data from a resurvey of the Bourbeuse River collected in 1997 yielded 
nine live sheepnose from four sites (Roberts and Bruenderman 2000, p. 
39) and fresh dead shells were located at an additional site. Sheepnose 
relative abundance was 0.4 percent. Live or fresh dead sheepnose were 
found between RM 1.4 to 66.3. This comparison indicates a decrease in 
the number of extant sites (7 to 4) and a range contraction of 18 river 
miles (29 km). The sheepnose in the Meramec and Bourbeuse Rivers 
represents a population cluster.

Lower Missouri River System

    Osage Fork Gasconade River: The Lower Missouri River system 
population is represented by a single sheepnose specimen and is near 
extirpation. This individual was located in 1999 at RM 21.2 in the 
Osage Fork, a tributary to the Gasconade River (Bruenderman et al. 
2001, p. 14). It is the only known record for sheepnose in the 
Gasconade River drainage for over 25 years.

Ohio River System

    Historically, the sheepnose was documented from the entire length 
of the Ohio River (its type locality), and was first collected there in 
the early 1800s. Ohio River sampling of 664 river miles (1,068 km) 
along the northern border of Kentucky yielded 41 sheepnose (Williams 
1969, p. 58). Most of these (29) were found in the upper portions of 
river (from RM 317 to 538), but the population extended downstream to 
RM 871. Relative abundance was 0.7 percent for the entire reach 
sampled. Currently, the mainstem Ohio River and 10 tributary streams 
have extant sheepnose populations.
    Ohio River mainstem: The sheepnose is generally distributed, but 
rare, in most mainstem pools of the Ohio River. The population appears 
to be more abundant in the lower section of the river with a smaller 
population in the upper Ohio River pools (McGregor 2008, pers. comm.; 
Schuster and Williams 1989, p. 24; Zeto et al. 1987, p. 184). Long term 
monitoring data from 1993 to 2007 at RM 176 shows the sheepnose is 
usually collected each survey,

[[Page 3405]]

recruitment is occurring, and the species comprises 1.0 percent of the 
mussels at the site (relative abundance) (Morrison 2008, pers. comm.). 
Live sheepnose have also been collected in recent years at RM 725 and 
RM 300 (Morrison 2008, pers. comm.). The population in the lower Ohio 
River mainstem is viable with documented recruitment, but the 
population overall continues to show signs of decline (Butler 2002b, p. 
    Allegheny River: The Allegheny River drains northwestern 
Pennsylvania and western New York and joins the Monongahela River at 
Pittsburgh to form the Ohio River. A recruiting and improving 
population of sheepnose exists within the middle Allegheny River 
(Villella 2008, pers. comm.). Sampling efforts from 2006-2008 at 63 
sites over 78 miles (125 km) of river produced sheepnose at 18 sites. A 
total of 244 individuals of 7 different age classes were collected 
(Villella 2008, pers. comm.) providing ample evidence of recent 
    Kanawha River: The Kanawha River is a major southern tributary of 
the Ohio River draining much of West Virginia and with headwaters in 
Virginia and North Carolina. The Kanawha River harbors a small, but 
recruiting and stable, population of sheepnose in Fayette County, West 
Virginia (Butler 2002b, p. 14). The Kanawha population appears to be 
limited to 5 river miles (8 km) immediately below Kanawha Falls 
(Clayton 2008c, pers. comm.). Sheepnose collections from this reach in 
1987 resulted in a density of 0.013 per sq. m (0.140 per sq. ft), and 
collections from 2005 found a density of 0.016 per sq. m (0.172 per sq. 
ft) (Clayton 2008c, pers. comm.).
    Licking River: The sheepnose is known from the lower half of the 
Licking River, a southern tributary of the Ohio River in northeastern 
Kentucky. Currently, the species is known from roughly five sites in 
the middle Licking River (McGregor 2008, pers. comm.). There is no 
documented evidence of recent recruitment, and, therefore, the 
sustainability of the population is unknown. It is possible this 
population represents a population cluster with the Ohio River.
    Green River: The Green River is a lower Ohio River tributary in 
west-central Kentucky. Currently, a recruiting and improving population 
remains over an approximately 25 river mile (40 river km) reach in the 
upper Green River from the vicinity of Mammoth Cave National Park 
upstream into Hart County (Butler 2002b, p. 15). An investigation of 
muskrat middens from 2002 and 2003 revealed 42 sheepnose shells, with 
39 of the 42 between 1.2 and 2.2 inches (3.0 and 5.6 cm) in length and 
described as juveniles (Layzer 2008, pers. comm.). Sampling over the 
past several years (2005-2007) has documented a number of beds 
experiencing recruitment (McGregor 2008, pers. comm.).
    Tippecanoe River: The Tippecanoe River drains the central portion 
of northern Indiana in the upper Wabash River system. This population 
of sheepnose is considered stable with relatively recent recruitment 
(Butler 2002b, p. 17). Survey work between 1987 and 1995 documented 
sheepnose at 14 sites throughout the river and extended the known range 
of the species upstream into Marshall County (Butler 2002b, p. 17). The 
sheepnose is now known from 45 miles (72 km) of the Tippecanoe River 
(Ecological Specialists, Inc. 1993, pp. 80-81; Cummings and Berlocher 
1990, pp. 84, 98; Cummings 2008, pers. comm.; Fisher 2008, pers. 
    Kentucky, Wabash, Eel, Muskingum, and Walhonding Rivers: In 
addition to the aforementioned populations, sheepnose in the Ohio River 
system are known from the Kentucky, Wabash, and Eel Rivers, which are 
each represented by two or fewer specimens collected in the past 25 
years. Populations of the sheepnose in these three river systems are 
considered to be declining and may be nearing extirpation (Butler 
2002b, p. 15-16). A population cluster in two additional rivers, the 
Muskingum River and its tributary, the Walhonding River, have unknown 
populations. Although Watters and Dunn (1995, p. 240) documented 
recruitment in the lower Muskingum River in the mid-1980s, the 
sheepnose population in the river is extremely small, and distribution 
has been reduced to only the lower portion of the river where six 
individuals were collected in 1992 (Watters and Dunn 1995, pp. 253-

Cumberland River System

    Historical sheepnose records in the system are known from 
throughout the mainstem downstream of Cumberland Falls and three of its 
tributaries (Obey, Harpeth, and Caney Fork Rivers). Wilson and Clark 
(1914, pp. 15-19, 57) reported the species to be generally uncommon 
from 14 mainstem sites from what is now Cumberland Reservoir, Kentucky, 
downstream to Stewart County, Tennessee, a distance of nearly 500 miles 
(~805 km). Sheepnose was last documented in the Tennessee portion of 
the river during the early 1980s (Butler 2002b, p. 67).
    The only recent record for the Cumberland River is from 1987, at 
the extreme lower end of the river near its confluence with the Ohio 
River, below Barkley Dam (Butler 2002b, p. 18). This population may be 
influenced by the lower Ohio River sheepnose population (Butler 2002b, 
p. 18) and represents a population cluster. Surveys conducted in 2007-
2009 found no sheepnose (Hubbs, 2010, pers. comm.) and so this 
population may be extirpated.

Tennessee River System

    The sheepnose was originally known from the Tennessee River and 10 
of its tributary streams. Historically, Ortmann (1925, p. 328) 
considered the sheepnose to occur ``sparingly'' in the lower Tennessee 
River, and to be ``rare'' in the upper part of the system (Ortmann 
1918, p. 545). Hundreds of miles of large river habitat on the 
Tennessee River mainstem have been converted under nine reservoirs, 
with additional dams constructed in tributaries historically harboring 
the sheepnose (for example, Clinch, Holston, Little Tennessee, Hiwassee 
Rivers) (Tennessee Valley Authority 1971, p. 5). Sheepnose populations 
currently persist in limited reaches of the Tennessee River mainstem 
and four tributaries.
    Tennessee River mainstem: The 53-mile (85-km) stretch of river in 
northwestern Alabama referred to as the Muscle Shoals, historically 
harbored 69 species of mussels, making it the most diverse mussel fauna 
ever known (Garner and McGregor 2001, pp. 155-157). However, with the 
construction of three dams (Wilson in 1925, Wheeler in 1930, and 
Pickwick Landing in 1940) most of the historical habitat was inundated, 
leaving only small, flowing habitat remnants (Garner and McGregor 2001, 
p. 158).
    The species is found only occasionally in the lower Tennessee River 
below Pickwick Landing Dam in southwestern Tennessee. Scruggs (1960, p. 
11) recorded a relative abundance of 0.2 percent, while Yokley (1972, 
p. 64) considered it to be ``very rare'' in this reach (relative 
abundance of 0.1 percent). Yokley reported only two specimens that were 
each estimated to be 20 or more years old.
    The sheepnose persists in the tailwaters of Guntersville, Wilson, 
Pickwick Landing, and Kentucky Dams on the mainstem Tennessee River, 
where it is considered uncommon (Garner & McGregor 2001, p. 165; Gooch 
et al. 1979, p. 9). These populations are considered stable overall but 
with very limited recruitment (Garner and McGregor 2001, p. 165; 
McGregor 2008, pers. comm.). The species has been found in low numbers 
over the past 80 years from relic habitat in the Wilson Dam tailwaters, 
a several-mile reach

[[Page 3406]]

adjacent to and downstream from Florence, Alabama (Butler 2002b, pp. 
    Clinch River: The Clinch River in southwestern Virginia and 
northeastern Tennessee is one of the largest and most significant 
tributaries of the upper Tennessee River system. Based on archeological 
evidence, the sheepnose was ``extremely rare'' in the lower Clinch 
River (Parmalee and Bogan 1986, p. 28). As of 2002, the largest lots of 
museum material available for the sheepnose had been from the Clinch 
River and its tributary, the Powell River (Watters 2010, pers. comm.). 
Individual Clinch River museum lots collected during 1963 to 1969 
include 36, 39, 70, and 82 fresh dead specimens. The sheepnose 
population in the Clinch River currently occurs over approximately 60 
river miles (96 km) from northern Scott County, Virginia downstream 
into Hancock County, Tennessee, and is considered stable with recently 
documented recruitment (Eckert 2008, pers. comm.). Survey work between 
1979 and 1994 (Ahlstedt & Tuberville 1997, p. 73) reported low 
densities of 0.009 to 0.018 individuals per sq. ft. (0.1 to 0.2 per sq. 
m). Sampling efforts in 2005 and 2006 reported densities from two sites 
(RM 223.6 and 213.2) in Scott County, Virginia, of 0.021 and 0.006 
individuals per sq. m (0.226 and 0.064 per sq. ft), respectively 
(Eckert 2008, pers. comm.). Relative abundance for sheepnose at these 
locations was 1.5 percent and 1.0 percent, respectively.
    Powell River: The largest sheepnose collection (OSUM) known 
rangewide was collected in the Powell River, the Clinch River's largest 
tributary, and included 6 live and 141 fresh dead specimens. Today, the 
sheepnose population in the Powell River is considered stable, and 
recruitment has been documented. In 1979, Ahlstedt (1991b, pp. 129-130) 
reported 45 live specimens from 17 of 78 sites (an average 2.6 
individuals per site). Ahlstedt and Tuberville (1997, p. 96) conducted 
quantitative sampling in the Powell between 1979 and 1994, and found 
the sheepnose at densities of 0.01 to 0.08 per sq. m (0.107 and 0.861 
per sq. ft). Sampling efforts in 2004 reported densities from two sites 
in Lee County, Virginia (RM 120.3 and 117.3), of 0.012 and 0.017 
individuals per sq. m (0.129 and 0.183 per sq. ft), respectively 
(Eckert 2008, pers. comm.). Relative abundance for sheepnose was 0.82 
percent and 0.99 percent, respectively.
    Duck River: The Duck River population is recently represented by 
the collection of single 10+ year old animal in 2003. The sheepnose was 
likely always rare in the Duck River and, previous to 2003, the species 
was thought to be extirpated. The current status of the population is 
    Holston River: In July 2002, sampling in Holston River produced 
live sheepnose at 16 of 20 sites sampled below the Cherokee Dam. This 
reach extended from Nance Ferry to Monday Island (RM 14.6), Jefferson 
and Knox Counties (Fraley 2008, pers. comm.). A total of 206 specimens 
were found with an overall relative abundance of 18.2 percent among the 
18 species reported live from this reach. The collection was comprised 
of extremely old individuals with no recently recruited individuals 
being found. Although the population appeared significant in numbers, 
the lack of recruitment in this population is indicative of a remnant 
population on its way to extirpation (Butler 2002b, p. 19). In 2007, 
Tennessee Valley Authority biologists located sheepnose in the Holston 
River while conducting fish surveys; however, no additional mussel 
survey work has been completed in the area since 2002 (Baxter 2010, 
pers. comm.).

Lower Mississippi River System

    The sheepnose was apparently never widely distributed in the lower 
Mississippi River system. The only verified records are for Hatchie 
River in Tennessee and the Delta region in Mississippi. The only 
records for the Yazoo and Big Black Rivers are from archeological sites 
(Butler 2002b, p. 21). The sheepnose population in the Big Sunflower 
River, Mississippi, is the only one remaining in the lower Mississippi 
River system. Once abundant judging from museum and archeological 
records, there is now only a small declining population in the Big 
Sunflower River (Jones 2008, pers. comm.). The population is believed 
to be limited to a 12- to 15-mile (19- to 24-km) reach upstream of 
Indianola in Sunflower County, Mississippi. Although no juvenile 
mussels have been found in recent sampling efforts, variably-sized 
individuals indicate some, possibly very low, level of recruitment in 
the population (Jones 2008, pers. comm.).

Summary of Extant Sheepnose Populations

    The sheepnose has experienced a significant reduction in range, and 
many of the extant populations are disjunct, isolated, and appear to be 
declining. The extirpation of this species from over 50 streams (more 
than 65 percent) within its historical range indicates that substantial 
population losses have occurred. In the majority of streams with extant 
populations, the sheepnose appears to be uncommon at best. Only in the 
Allegheny and Green Rivers is the species considered to be improving in 
population status. Several other extant populations are thought to 
exhibit some level of stability and have experienced relatively recent 
recruitment (Chippewa/Flambeau, Meramec, Ohio, Tippecanoe, Clinch, and 
Powell Rivers). Given the compilation of current distribution, 
abundance, and status trend information, the sheepnose appears to 
exhibit a high level of imperilment.

Previous Federal Actions

    We identified the spectaclecase and sheepnose as candidate species 
in a notice of review published in the Federal Register on May 4, 2004 
(69 FR 24875). The spectaclecase and sheepnose remained candidate 
species in subsequent notices, including: May 11, 2005 (70 FR 24869), 
September 12, 2006 (71 FR 53755), December 6, 2007 (72 FR 69033), 
December 10, 2008 (73 FR 75176), and November 9, 2009 (74 FR 57804). A 
candidate species is a species for which we have on file sufficient 
information on biological vulnerability and threats to support issuing 
a proposed rule to list the species as endangered or threatened.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1533), and its implementing 
regulations at 50 CFR part 424, set forth the procedures for adding 
species to the Federal lists of Endangered and Threatened Wildlife and 
Plants. Under section 4(a)(1) of the Act, we may determine a species to 
be endangered or threatened due to one or more of the following five 
factors: (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) the inadequacy of existing regulatory 
mechanisms; or (E) other natural or manmade factors affecting its 
continued existence. Listing actions may be warranted based on any of 
the above threat factors, singly or in combination. Each of these 
factors is discussed below.

A. The Present or Threatened Destruction, Modification, or Curtailment 
of Its Habitat or Range.

    The decline of mussels such as the spectaclecase and sheepnose is 
primarily the result of habitat loss and degradation (Neves 1991, pp. 
252, 265). Chief among the causes of decline are impoundments, 
channelization, chemical contaminants, mining, oil and

[[Page 3407]]

gas development, and sedimentation (Neves 1991, pp. 252, 260-261; Neves 
1993, pp. 1-7; Neves et al. 1997, pp. 63-72; Strayer et al. 2004, pp. 
435-437; Watters 2000, pp. 261-268; Williams et al. 1993, p. 7). These 
threats to mussels in general (and spectaclecase and sheepnose where 
specifically known) are individually discussed below.
Dams and Impoundments
    Dams eliminate or reduce river flow within impounded areas, trap 
silts and cause sediment deposition, alter water temperature and 
dissolved oxygen levels, change downstream water flow and quality, 
decrease habitat heterogeneity, affect normal flood patterns, and block 
upstream and downstream movement of species (Layzer et al. 1993, pp. 
68-69; Neves et al. 1997, pp. 63-64; Watters 2000, pp. 261-264). Within 
impounded waters, decline of freshwater mollusks has been attributed to 
sedimentation, decreased dissolved oxygen, and alteration in resident 
fish populations (Neves et al. 1997, pp. 63-64; Pringle et al. 2009, 
pp. 810-815; Watters 2000, pp. 261-264). Dams significantly alter 
downstream water quality and habitats (Allen & Flecker 1993, p. 36), 
and negatively affect tailwater mussel populations (Layzer et al. 1993, 
p. 69; Neves et al. 1997, p. 63; Watters 2000, pp. 265-266). Below 
dams, mussel declines are associated with changes and fluctuation in 
flow regime, scouring and erosion, reduced dissolved oxygen levels and 
water temperatures, and changes in resident fish assemblages (Layzer et 
al. 1993, p. 69; Neves et al. 1997, pp. 63-64; Pringle et al. 2009, pp. 
810-815; Watters 2000, pp. 265-266; Williams et al. 1992, p. 7). The 
decline and imperilment of freshwater mussels in several tributaries 
within the Tennessee, Cumberland, Mississippi, Missouri, and Ohio River 
basins have been directly attributed to construction of numerous 
impoundments in those river systems (Hanlon et al. 2009, pp. 11-12; 
Layzer et al. 1993, pp. 68-69; Miller et al. 1984, p. 109; Neves et al. 
1997, pp. 63-64; Sickel et al. 2007, pp. 71-78; Suloway 1981, pp. 237-
238; Watters 2000, pp. 262-263; Watters & Flaute 2010, pp. 3-7; 
Williams & Schuster 1989, pp. 7-10).
    Population losses due to impoundments have likely contributed more 
to the decline and imperilment of the spectaclecase and the sheepnose 
than any other factor. Large river habitat throughout nearly all of the 
range of both species has been impounded, leaving generally short, 
isolated patches of vestigial habitat in the area below dams. 
Navigational locks and dams, (for example, on the upper Mississippi, 
Ohio, Allegheny, Muskingum, Kentucky, Green, and Barren Rivers), some 
high-wall dams (for example, on the Wisconsin, Kaskaskia, Walhonding, 
and Tippecanoe Rivers), and many low-head dams (for example, on the St. 
Croix, Chippewa, Flambeau, Wisconsin, Kankakee, and Bourbeuse Rivers) 
have contributed significantly to the loss of sheepnose and 
spectaclecase habitat (Butler 2002a, pp. 11-20 2002b, pp. 9-25).
    The majority of the Tennessee and Cumberland River main stems and 
many of their largest tributaries are now impounded. There are 36 major 
dams located in the Tennessee River system and about 90 percent of the 
Cumberland River downstream of Cumberland Falls (RM 550 (RKM 886)) is 
either directly impounded by U.S. Army Corps of Engineers (Corps) 
structures or otherwise impacted by cold tail water released from 
several dams. Major Corps impoundments on Cumberland River tributaries 
(for example, Stones River and Caney Fork) have inundated an additional 
100 miles (161 km) or more of spectaclecase and sheepnose habitat. 
Coldwater releases from Wolf Creek, Dale Hollow (Obey River), and 
Center Hill (Caney Fork) Dams continue to degrade spectaclecase and 
sheepnose habitat in the Cumberland River system. Layzer et al. (1993, 
p. 68) reported that 37 of the 60 pre-impoundment mussel species of the 
Caney Fork River have been extirpated. Watters (2000, pp. 262-263) 
summarizes the tremendous loss of mussel species from various portions 
of the Tennessee and Cumberland River systems. Approximately one-third 
of the historical sheepnose and spectaclecase streams are in the 
Tennessee and Cumberland River systems.
    Navigational improvements on the Ohio River began in 1830, and now 
include 21 lock and dam structures stretching from Pittsburgh, 
Pennsylvania, to Olmsted, Illinois, near its confluence with the 
Mississippi River. Historically, habitat now under navigational pools 
once supported up to 50 species of mussels, including the spectaclecase 
and sheepnose. Tributaries to the Ohio River, such as the Green and 
Allegheny rivers, were also altered by impoundments. A series of six 
locks and dams was constructed on the lower half of the Green River 
decades ago and extend upstream to the western boundary of Mammoth Cave 
National Park (MCNP). The upper two locks and dams destroyed 
spectaclecase habitat, particularly Lock and Dam 6, which flooded the 
central and western portions of MCNP. Approximately 30 river miles (48 
km) of mainstem habitat were also eliminated with the construction of 
the Green River Dam in 1969. Locks and dams were also constructed on 
the lower reaches of the Allegheny, Kanawha, Muskingum, and Kentucky 
Rivers which disrupted historical riverine habitat for the sheepnose.
    Similarly, dams impound most of the upper Mississippi River and 
many of its tributaries. A series of 29 locks and dams constructed 
since the 1930s in the mainstem resulted in profound changes to the 
nature of the river, primarily replacing a free-flowing alluvial (flood 
plain) system with a stepped gradient (higher pool area to riffle area 
ratio) river. Modifications fragmented the mussel beds where 
spectaclecase and sheepnose were found in the Mississippi River, 
reduced stable riverine habitat, and disrupted fish host migration and 
habitat use.
    Dams and impoundments have fragmented and altered stream habitats 
throughout the Sac River Basin in the lower Missouri River system. 
Stockton Dam impounds 39 miles (63 km) of the upper Sac River and the 
Truman Dam inundates about 8 miles (13 km) of the lower Sac River and 
its tributaries (Hutson & Barnhart 2004, p. 7). The rarity of live 
spectaclecase in the Sac River, coupled with the large number of dead 
shells observed in a recent study, suggests that this species has 
decreased since the river was impounded, and that spectaclecase may 
soon be extirpated from the Sac River system (Hutson & Barnhart 2004, 
p. 17).
    Dam construction has a secondary effect of fragmenting the ranges 
of aquatic mollusk species, leaving relict habitats and populations 
isolated by the structures as well as by extensive areas of deep 
uninhabitable, impounded waters. These isolated populations are unable 
to naturally recolonize suitable habitat that is impacted by temporary, 
but devastating events, such as severe drought, chemical spills, or 
unauthorized discharges (Cope et al. 1997, pp. 235-237; Layzer et al. 
1993, pp. 68-69; Miller & Payne 2001, pp. 14-15; Neves et al. 1997, pp. 
63-75; Pringle et al. 2009, pp. 810-815; Watters 2000, pp. 264-265, 
268; Watters & Flaute 2010, pp. 3-7).
    Nonpoint source pollution from land surface runoff originates from 
virtually all land use activities and includes sediments; fertilizer, 
herbicide, and pesticide residues; animal or human wastes; septic tank 
leakage and gray water discharge; and oils and greases. Nonpoint source 
pollution can cause excess sedimentation, nutrification, decreased 
dissolved oxygen

[[Page 3408]]

concentration, increased acidity and conductivity, and other changes in 
water chemistry that can negatively impact freshwater mussels. Land use 
types around the sheepnose and spectaclecase populations include 
pastures, row crops, timber, and urban and rural communities.
    Excessive sediments are believed to impact riverine mollusks 
requiring clean, stable streams (Brim Box & Mosa 1999, p. 99; Ellis 
1936, pp. 39-40). Impacts resulting from sediments have been noted for 
many components of aquatic communities. For example, sediments have 
been shown to affect respiration, growth, reproductive success, and 
behavior of freshwater mussels, and to affect fish growth, survival, 
and reproduction (Waters 1995, pp. 173-175). Potential sediment sources 
within a watershed include virtually all activities that disturb the 
land surface, and most localities currently occupied by the 
spectaclecase and sheepnose are affected to varying degrees by 
    Sedimentation has been implicated in the decline of mussel 
populations nationwide, and is a threat to spectaclecase and sheepnose 
(Brim Box & Mosa 1999, p. 99; Dennis 1984, p. 212; Ellis 1936, pp. 39-
40; Fraley & Ahlstedt 2000, pp. 193-194; Poole & Downing 2004, pp. 119-
122; Vannote & Minshall 1982, pp. 4105-4106). Specific biological 
impacts include reduced feeding and respiratory efficiency from clogged 
gills, disrupted metabolic processes, reduced growth rates, limited 
burrowing activity, physical smothering, and disrupted host fish 
attractant mechanisms (Ellis 1936, pp. 39-40; Hartfield & Hartfield 
1996, p. 373; Marking & Bills 1979, p. 210; Vannote & Minshall 1982, 
pp. 4105-4106; Waters 1995, pp. 173-175). In addition, mussels may be 
indirectly affected if high turbidity levels significantly reduce the 
amount of light available for photosynthesis and thus the production of 
certain food items (Kanehl & Lyons 1992, p. 7).
    Studies indicate that the primary impacts of excess sediment on 
mussels are sublethal, with detrimental effects not immediately 
apparent (Brim Box & Mosa 1999, p. 101). The physical effects of 
sediment on mussels are multifold, and include changes in suspended and 
bed material load; changes in bed sediment composition associated with 
increased sediment production and run-off in the watershed; changes in 
the form, position, and stability of channels; changes in depth or the 
width-to-depth ratio, which affects light penetration and flow regime; 
actively aggrading (filling) or degrading (scouring) channels; and 
changes in channel position that may leave mussels stranded (Brim Box & 
Mosa 1999, pp. 109-112; Kanehl & Lyons 1992, pp. 4-5; Vannote & 
Minshall 1982, p. 4106). The Chippewa River in Wisconsin, for example, 
has a tremendous bedload composed primarily of sand that requires 
dredging to maintain barge traffic on the mainstem Mississippi below 
its confluence (Thiel 1981, p. 20). The mussel diversity in the 
Mississippi River below the confluence with the Chippewa River has 
predictably declined from historical times. Lake Pepin, a once natural 
lake formed in the upper Mississippi River upstream from the mouth of 
the Chippewa River, has become increasingly silted in over the past 
century, reducing habitat for the spectaclecase and sheepnose (Thiel 
1981, p. 20).
    Increased sedimentation and siltation may explain in part why 
spectaclecase and sheepnose mussels appear to be experiencing 
recruitment failure in some streams. Interstitial spaces in the 
substrate provide crucial habitat for juvenile mussels. When clogged, 
interstitial flow rates and spaces are reduced (Brim Box & Mosa 1999, 
p. 100), thus reducing juvenile habitat. Furthermore, sediment may act 
as a vector for delivering contaminants such as nutrients and 
pesticides to streams and juveniles may ingest contaminants adsorbed to 
silt particles during normal feeding activities. Female spectaclecase 
and sheepnose produce conglutinates that attract hosts. Such a 
reproductive strategy depends on clear water during the critical time 
of the year when mussels are releasing their glochidia.
    Agricultural activities are responsible for much of the sediment 
(Waters 1995, p. 170) and chemical discharge into streams, affecting 60 
percent of the impaired river miles in the country (EPA 2007, p. 10). 
Unrestricted livestock access occurs on many streams and potentially 
threatens their mussel populations (Fraley & Ahlstedt 2000, pp. 193-
194). Grazing may reduce infiltration rates and increase runoff; 
trampling and vegetation removal increases the probability of erosion 
(Armour et al. 1991, pp. 8-10; Brim Box & Mosa 1999, p. 103). The 
majority of the remaining spectaclecase and sheepnose populations are 
threatened by some form of agricultural runoff (nutrients, pesticides, 
sediment). Copper Creek, a tributary to the Clinch River, for example, 
has a drainage area that contains approximately 41 percent agricultural 
land (Hanlon et al. 2009, p. 3). Fraley and Ahlstedt (2000, p. 193) and 
Hanlon et al. (2009, pp. 11-12) attributed the decline of the Copper 
Creek mussel fauna to an increase in cattle grazing and resultant 
nutrient enrichment and loss of riparian vegetation along the stream, 
among other factors. This scenario is similar in other parts of the 
extant range of the spectaclecase and sheepnose.
    Sedimentation and urban runoff may also be threats to the sheepnose 
in the Kankakee River system as the Chicago Metro area continues to 
expand. Declines in mussel diversity observed in the Ohio River are in 
part due to pollution from urban centers; in many of these areas the 
loss of diversity has not recovered from water quality problems that 
began prior to dam construction (Watters & Flaute 2010, pp. 3-7).
    As the spectaclecase primarily inhabits deep water along the 
outside of bends, it may be particularly vulnerable to siltation. The 
current often slackens in this habitat, more so than in riffles and 
runs where other mussel species are typically found, and suspended 
sediment settles out. Spectaclecase beds covered with a thick layer of 
silt have been observed in Missouri, often downstream from reaches with 
eroding banks (Roberts 2008, pers. comm.).
    Dredging and channelization activities have profoundly altered 
riverine habitats nationwide. Hartfield (1993, pp. 131-139), Neves et 
al. (1997, pp. 71-72), and Watters (2000, pp. 268-269) reviewed the 
specific effects of channelization on freshwater mussels. 
Channelization impacts stream physically (for example accelerated 
erosion, reduced depth, decreased habitat diversity, geomorphic 
instability, and loss of riparian vegetation) and biologically (for 
example decreased fish and mussel diversity, altered species 
composition and abundance, decreased biomass, and reduced growth rates) 
(Hartfield 1993, pp. 131-139). Channel construction for navigation 
increases flood heights (Belt 1975, p. 684), partly as a result of a 
decrease in stream length and an increase in gradient (Hubbard et al. 
1993, p. 137 (in Hartfield 1993, p. 131)). Flood events may thus be 
exacerbated, conveying into streams large quantities of sediment, 
potentially with adsorbed contaminants. Channel maintenance may result 
in profound impacts downstream (Stansbery 1970, p. 10), such as 
increases in turbidity and sedimentation, which may smother bottom-
dwelling organisms.
    Channel maintenance operations for commercial navigation have 
impacted habitat for the sheepnose and spectaclecase in many large 

[[Page 3409]]

rangewide. Periodic channel maintenance may continue to adversely 
affect this species in the upper Mississippi, Ohio, Muskingum, and 
Tennessee rivers. Further modifications to the Mississippi River 
channel are anticipated with the recently authorized Navigation and 
Environmental Sustainability Program (NESP) (Water Resources 
Development Act of 2007 (Pub. L. 110-114)), which will consist of 
construction of larger locks and other navigation improvements 
downstream of MRP 14. Continual maintenance of the Mississippi River 
navigation channel requires dredging, wing and closing dam 
reconstruction and maintenance, and bank armoring. Dredging, 
maintenance, and construction activities destabilize instream fine 
sediments are likely to adversely affect the spectaclecase and the 
sheepnose. Spectaclecase tend to inhabit relatively deep water where 
they are particularly vulnerable to siltation. The current is slower in 
this habitat than in riffles and runs, and suspended sediment settles 
out in greater volume. Dredging to maintain barge traffic on the 
Mississippi River below the mouth of the Chippewa River in Wisconsin 
has reduced mussel diversity due to the increase in unstable sand 
substrates (Thiel 1981, p. 20; U.S. Army Corps of Engineers 1996, p. 1, 
Tab 14).
    Channel maintenance dredging is also a major concern for mussel 
populations. A large amount of spoil (dredged earth and rock) was 
dumped directly on a mussel bed in the Muskingum River that included 
the sheepnose in the late 1990s (Watters 2008, pers. comm.). Thousands 
of mussels were killed as the result of this single event. Watters and 
Dunn (1995 p. 231) also noted that the lower ends of two mussel beds 
coincided with the mouths of Wolf and Bear Creeks. This led them to 
surmise that pollutants, such as sediment loads or agricultural runoff, 
in their watersheds may adversely impact mussels in the mainstem 
Muskingum River below the confluences of Wolf Creek and Bear Creek.
    Mussels require a stable substrate to survive and reproduce and are 
particularly susceptible to channel instability (Neves et al. 1997, p. 
23; Parmalee & Bogan 1998). Channel and bank degradation have led to 
the loss of stable substrates in the Meramec River Basin. Roberts and 
Bruenderman (2000, pp. 7-8, 21-23) pointed to the loss of suitable 
stable habitat as a major cause of decline in mussel abundance at sites 
previously surveyed in 1979.
    The Tennessee River was once a stronghold for the spectaclecase 
(Ortmann 1924, p. 60; 1925, p. 327), and the sheepnose was originally 
known to occur in the Tennessee River and 10 of its tributaries 
(Ortmann 1925, p. 328). The mainstem of the Tennessee River is 
maintained as a navigational channel, and a plan to deepen it has been 
proposed (Hubbs 2008, pers. comm.). Severe bank erosion is ongoing 
along some reaches of the river below Pickwick Landing Dam, with some 
sites losing several feet of stream bank per year (Hubbs 2008, pers. 
    The sheepnose population within the Big Sunflower River is 
threatened by a Corps flood control project (Jones 2008, pers. comm.). 
Dredging for this project is planned to take place downstream of 
Indianaola, but head-cutting may ultimately destabilize the substrate 
in which sheepnose now exists. This activity, coupled with other 
threats potentially affecting sheepnose (see below), may lead to 
extirpation of the population within 10 years (Jones 2008, pers. 
    The upper Kankakee River in Indiana was channelized several decades 
ago. The sheepnose is now considered extirpated from the upper 
Kankakee, and is restricted to the unchannelized portion of the river 
in Illinois (Cummings 2008, pers. comm.).
    Instream gravel mining has been implicated in the destruction of 
mussel populations (Hartfield 1993, pp. 136-138). Negative impacts 
associated with gravel mining include stream channel modifications 
(altered habitat, disrupted flow patterns, and sediment transport), 
water quality modifications (increased turbidity, reduced light 
penetration, and increased temperature), macroinvertebrate population 
changes (elimination, habitat disruption, and increased sedimentation), 
and changes in fish populations (impacts to spawning and nursery 
habitat and food web disruptions) (Kanehl & Lyons 1992, pp. 4-10).
    Heavy metal-rich drainage from coal mining and associated 
sedimentation has adversely impacted portions of the Tennessee River 
system in Virginia. Low pH commonly associated with mine runoff can 
reduce glochidial encystment (attachment) rates (Huebner & Pynnonen 
1992, pp. 2350-2353). Acid mine runoff may thus have local impacts on 
recruitment of the mussel populations close to mines.
    Coal-related toxins in the Clinch River may explain the decline and 
lack of mussel recruitment at some sites in the Virginia portion of 
that stream (Ahlstedt 2008, pers. comm.). Patterns of mussel 
distribution and abundances have been found to be negatively correlated 
with proximity to coal-mining activities (Ahlstedt & Tuberville 1997, 
pp. 74-75). Known mussel toxicants, such as polycyclic aromatic 
hydrocarbons, heavy metals (for example, copper, manganese, and zinc), 
and other chemicals from coal mining and other activities contaminate 
sediments in the Clinch River (Ahlstedt & Tuberville 1997, p. 75). 
These chemicals are toxic to juvenile mussels (Ahlstedt & Tuberville 
1997, p. 75). Pollutant inputs to the Clinch River from a coal-burning 
power plant in Carbo, Virginia, were shown to increase mortality and 
reduce cellulolytic activity (breaking down cellulose) in transplanted 
mussels (Farris et al. 1988, pp. 705-706). Site-specific copper 
toxicity studies of unionid glochidia in the Clinch River showed that 
freshwater mussels as a group were generally sensitive to copper, the 
toxic constituent of the power plant effluent (Cherry et al. 2002, p. 
596). All of these studies indicate that acid mine runoff may have 
local impacts on spectaclecase recruitment and survival in this river.
    Gravel-mining activities may also be a localized threat in some 
streams with extant sheepnose and spectaclecase populations. Gravel 
mining causes stream instability, increasing erosion, turbidity, and 
subsequent sediment deposition (Meador & Layher 1998, pp. 8-9). Gravel 
mining is common in the Meramec River system. Between 1997 and 2008, 
the Missouri Department of Natural Resources issued permits for 102 
sand- and gravel-mining sites in the Meramec River (Zeaman 2008, pers. 
comm.). Although rigid guidelines prohibited instream mining and 
required streamside buffers, a court ruling deauthorized the Corps from 
regulating these habitat protective measures. The Corps still retains 
oversight for gravel mining, but many mining operations do not fall 
under Corps jurisdiction (Roberts & Bruenderman 2000, p. 23). In the 
lower Tennessee River, mining is permitted in 18 reaches for a total of 
47.9 river miles (77.1 km) between the Duck River confluence and 
Pickwick Landing Dam, a distance of over 95 miles (153 km) (Hubbs 2008, 
pers. comm.). This is the reach where mussel recruitment has been noted 
for many rare species in recent years. These activities have the 
potential to impact the river's small sheepnose population. The 
Gasconade River and its tributaries have been subject to gravel mining 
and other channel modifying practices that accelerate channel 
destabilization. These physical habitat threats combined with poor 
water quality and agricultural

[[Page 3410]]

nonpoint source pollution are serious threats to all existing mussel 
fauna in the system.
Oil and Gas Development
    Coal, oil, and natural gas resources are present in some of the 
watersheds that are known to support sheepnose, including the Allegheny 
River. Exploration and extraction of these energy resources can result 
in increased siltation, a changed hydrograph, and altered water quality 
even at a distance from the mine or well field. Sheepnose habitat in 
larger streams can be threatened by the cumulative effects of multiple 
mines and well fields (adapted from Service 2008, p. 11).
    Coal, oil, and gas resources are present in a number of the basins 
where sheepnose occur, and extraction of these resources has increased 
dramatically in recent years, particularly in Pennsylvania and West 
Virginia. Although oil and gas extraction generally occurs away from 
the river, extensive road networks are required to construct and 
maintain wells. These road networks frequently cross or occur near 
tributaries, contributing sediment to the receiving waterway. In 
addition, the construction and operation of wells may result in the 
discharge of brine. Point source discharges are typically regulated; 
however, nonpoint inputs such as silt and other contaminants may not be 
sufficiently regulated, particularly those originating some distance 
from a waterway. In 2006, more than 3,700 permits were issued for oil 
and gas wells by the Pennsylvania Department of Environmental 
Protection, which also issued 98 citations for permit violations at 54 
wells (Hopey 2007; adapted from Service 2008, p. 12).
Chemical Contaminants
    Chemical contaminants are ubiquitous throughout the environment and 
are considered a major threat in the decline of freshwater mussel 
species (Cope et al. 2008, p. 451; Richter et al. 1997, p. 1081; 
Strayer et al. 2004, p. 436; Wang et al. 2007a, p. 2029). Chemicals 
enter the environment through both point and nonpoint discharges 
including spills, industrial sources, municipal effluents, and 
agricultural runoff. These sources contribute organic compounds, heavy 
metals, pesticides, and a wide variety of newly emerging contaminants 
to the aquatic environment. As a result, water and sediment quality can 
be degraded to the extent that mussel populations are adversely 
    Chemical spills can be especially devastating to mussels because 
they may result in exposure of a relatively immobile species to 
extremely elevated concentrations that far exceed toxic levels and any 
water quality standards that might be in effect. Some notable spills 
that released large quantities of highly concentrated chemicals 
resulting in mortality to mussels include:
     Massive mussel kills on the Clinch River at Carbo, 
Virginia occurred from a power plant alkaline fly ash pond spill in 
1967, and a sulfuric acid spill in 1970 (Crossman et al. 1973, p. 6);
     Approximately 18,000 mussels of several species, including 
750 individuals from three endangered mussel species, were eliminated 
from the upper Clinch River near Cedar Bluff, Virginia in 1998, when an 
overturned tanker truck released 1,600 gallons (6,056 liters) of a 
chemical used in rubber manufacturing (Jones et al. 2001, p. 20; 
Schmerfeld 2006, p. 12); and
     An on-going release of sodium dimethyl dithiocarbamate, a 
chemical used to reduce and precipitate hexachrome, starting in 1999 
impacted approximately 10 river miles (16 km) of the Ohio River and 
resulted in an estimated loss of one million mussels, including 
individuals from two federally listed species (DeVault 2009, pers. 
comm.; Clayton 2008b, pers. comm.).
    These are not the only instances where chemical spills have 
resulted in the loss of high numbers of mussels (Brown et al. 2005, p. 
1457; Jones et al. 2001, p. 20; Neves 1991, p. 252; Schmerfeld 2006, 
pp. 12-13), but are provided as examples of the serious threat chemical 
spills pose to mussel species. The sheepnose and spectaclecase are 
especially threatened by chemical spills because these spills can occur 
anywhere that highways with tanker trucks, industries, or mines overlap 
with sheepnose and spectaclecase distribution.
    Exposure of mussels to lower concentrations of contaminants more 
likely to be found in aquatic environments can also adversely affect 
mussels and result in the decline of freshwater mussel species. Such 
concentrations may not be immediately lethal, but over time, can result 
in mortality, reduced filtration efficiency, reduced growth, decreased 
reproduction, changes in enzyme activity, and behavioral changes to all 
mussel life stages. Frequently, procedures which evaluate the ``safe'' 
concentration of an environmental contaminant (for example, national 
water quality criteria) do not have data for freshwater mussel species 
or exclude data that are available for freshwater mussels (March et al. 
2007, pp. 2066-2067, 2073).
    Current research is now starting to focus on the contaminant 
sensitivity of freshwater mussel glochidia and newly-released juvenile 
mussels (Goudreau et al. 1993, pp. 219-222; Jacobson et al. 1997, p. 
2390; March et al. 2007, pp. 2068-2073; Valenti et al. 2006, pp. 2514-
2517; Valenti et al. 2005, pp. 1244-1245; Wang et al. 2007c, pp. 2041-
2046) and juveniles (Augspurger et al. 2003, p. 2569; Bartsch et al. 
2003, p. 2561; March et al. 2007, pp. 2068-2073; Mummert et al. 2003, 
p. 2549; Valenti et al. 2006, pp. 2514-2517; Valenti et al. 2005, pp. 
1244-1245; Wang et al. 2007b, pp. 2053-2055; Wang et al. 2007c, pp. 
2041-2046) to such contaminants as ammonia, metals, chlorine, and 
pesticides. The toxicity information presented in this section focuses 
on recent water-only laboratory acute (sudden and severe exposure) and 
chronic (prolonged or repeated exposure) toxicity tests with early life 
stages of freshwater mussels using the standard testing methodology 
published by the American Society for Testing and Materials (ASTM) 
(American Society for Testing and Materials. 2008. Standard guide for 
conducting laboratory toxicity tests with freshwater mussels E2455-06. 
In Annual Book of ASTM Standards, Vol 11.06. Philadelphia, PA, pp. 
1442-1493.) Use of this standard testing method generates consistent, 
reliable toxicity data with acceptable precision and accuracy (Wang et 
al. 2007a, p. 2035) and was used for toxicity tests on ammonia, copper, 
chlorine and select pesticides (Augspurger et al. 2007, p. 2025; 
Bringolf et al. 2007b, p. 2101; Bringolf et al. 2007c, p. 2087; Wang et 
al. 2007a, p. 2029; Wang et al. 2007b, p. 2048; Wang et al. 2007c, p. 
2036). Use of these tests has documented that, while mussels are 
sensitive to some contaminants, they are not universally sensitive to 
all contaminants (Augspurger et al. 2007, pp. 2025-2026).
    One chemical that is particularly toxic to early life stages of 
mussels is ammonia. Sources of ammonia include agricultural wastes 
(animal feedlots and nitrogenous fertilizers), municipal wastewater 
treatment plants, and industrial waste (Augspurger et al. 2007, p. 
2026) as well as precipitation and natural processes (decomposition of 
organic nitrogen) (Augspurger et al. 2003, p. 2569; Goudreau et al. 
1993, p. 212; Hickey & Martin 1999, p. 44; Newton 2003, p. 1243). 
Therefore, ammonia is considered a limiting factor for survival and 
recovery of some mussel species due to its ubiquity in aquatic 
environments and high level of toxicity, and because the highest

[[Page 3411]]

concentrations typically occur in mussel microhabitats (Augspurger et 
al. 2003, p. 2574). In addition, studies have shown that ammonia 
concentrations increase with increasing temperature and low flow 
conditions (Cherry et al. 2005, p. 378; Cooper et al. 2005, p. 381), 
which may be exacerbated by the effects of climate change, and may 
cause ammonia to become more problematic for juvenile mussels. The EPA-
established ammonia water quality criteria (EPA 1985, pp. 94-99) may 
not be protective of mussels (Augspurger et al. 2003, p. 2572; Sharpe 
2005, p. 28) under current and future climate conditions.
    Mussels are also affected by metals (Keller & Zam 1991, p. 543), 
such as cadmium, chromium, copper, mercury, and zinc, which can 
negatively affect biological processes such as growth, filtration 
efficiency, enzyme activity, valve closure, and behavior (Jacobson et 
al. 1997, p. 2390; Keller & Zam 1991, p. 543; Naimo 1995, pp. 351-355; 
Valenti et al. 2005, p. 1244). Metals occur in industrial and 
wastewater effluents and are often a result of atmospheric deposition 
from industrial processes and incinerators. Glochidia and juvenile 
freshwater mussels have recently been studied to determine the acute 
and chronic toxicity of copper to these life stages (Wang et al. 2007b, 
pp. 2048-2056; Wang et al. 2007c, pp. 2036-2047). The chronic values 
determined for copper ranged from 8.5 to 9.8 micrograms per liter (ug/
L) for survival and from 4.6 to 8.5 ug/L for growth of juveniles. These 
chronic values are below the EPA 1996 chronic water quality criterion 
of 15 ug/L (hardness 170 mg/L) for copper (Wang et al. 2007b, pp. 2052-
2055). March (2007, pp. 2066, 2073) identifies that copper water 
quality criteria and modified State water quality standards may not be 
protective of mussels.
    Mercury is another heavy metal that has the potential to negatively 
affect mussel populations, and it is receiving attention due to its 
widespread distribution and potential to adversely impact the 
environment. Mercury has been detected throughout aquatic environments 
as a product of municipal and industrial waste and atmospheric 
deposition from coal-burning plants. One recent study evaluated the 
sensitivity of early life stages of mussels to mercury (Valenti et al. 
2005, p. 1242). This study determined that for the mussel species used 
(rainbow mussel, Villosa iris) glochidia were more sensitive to mercury 
than were juvenile mussels, with the median lethal concentration value 
of 14 ug/L compared to 114 ug/L for the juvenile life stage. The 
chronic toxicity tests conducted determined that juveniles exposed to 
mercury greater than or equal to 8 ug/L exhibited reduced growth. These 
observed toxicity values are below EPA's Criteria Continuous 
Concentration and Criteria Maximum Concentration, which are 0.77 ug/L 
and 1.4 ug/L, respectively. Based on these data, we believe that EPA's 
water quality standards for mercury should be protective of juvenile 
mussels and glochidia, except in cases of illegal dumping, permit 
violations, or spills. However, impacts to mussels from mercury 
toxicity may be occurring in some streams. According to the National 
Summary Data reported by States to the EPA, 3,770 monitored waters do 
not meet EPA standards for mercury in the United States. (http://iaspub.epa.gov/waters10/attains_nation_cy.control?p_report_type=T, 
accessed 6/28/2010). Acute mercury toxicity was determined to be the 
cause of extirpation of a diverse mussel fauna for a 70-mile (112-km) 
portion of the North Fork Holston River (Brown et al. 2005, pp. 1455-
    In addition to ammonia, agricultural sources of chemical 
contaminants include two broad categories that have the potential to 
adversely impact mussel species: Nutrients and pesticides. Nutrients 
(such as nitrogen and phosphorus) can impact streams when their 
concentrations reach levels that cannot be assimilated, a condition 
known as over-enrichment. Nutrient over-enrichment is primarily a 
result of runoff from livestock farms, feedlots, and heavily fertilized 
row crops (Peterjohn & Correll 1984, p. 1471). Over-enriched conditions 
are exacerbated by low-flow conditions, such as those experienced 
during typical summer-season flows and that might occur with greater 
frequency and magnitude as a result of climate change. Bauer (1988, p. 
244) found that excessive nitrogen concentrations can be detrimental to 
the adult freshwater pearl mussel (Margaritifera margaritifera), as was 
evident by the positive linear relationship between mortality and 
nitrate concentration. Also, a study of mussel life span and size 
(Bauer 1992, p. 425) showed a negative correlation between growth rate 
and eutrophication, and longevity was reduced as the concentration of 
nitrates increased. Nutrient over-enrichment can result in an increase 
in primary productivity, and the subsequent respiration depletes 
dissolved oxygen levels. This may be particularly detrimental to 
juvenile mussels that inhabit the interstitial spaces in the substrate 
where lower dissolved oxygen concentrations are more likely than on the 
sediment surface where adults tend to live (Sparks & Strayer 1998, pp. 
    Elevated concentrations of pesticide frequently occur in streams 
due to pesticide runoff, overspray application to row crops, and lack 
of adequate riparian buffers. Agricultural pesticide applications often 
coincide with the reproductive and early life stages of mussel, and 
thus impacts to mussels due to pesticides may be increased (Bringolf et 
al. 2007a, p. 2094). Little is known regarding the impact of currently 
used pesticides to freshwater mussels even though some pesticides, such 
as glyphosate (Roundup), are used globally. Recent studies tested the 
toxicity of glyphosate, its formulations, and a surfactant (MON 0818) 
used in several glyphosate formulations, to early life stages of the 
fatmucket (Lampsilis siliquoidea), a native freshwater mussel (Bringolf 
et al. 2007a, p. 2094). Studies conducted with juvenile mussels and 
glochidia determined that the surfactant (MON 0818) was the most toxic 
of the compounds tested and that L. siliquoidea glochidia were the most 
sensitive organism tested to date (Bringolf et al. 2007a, p. 2094). 
Roundup, technical grade glyphosate isopropylamine salt, and 
isopropylamine were also acutely toxic to juveniles and glochidia 
(Bringolf et al. 2007a, p. 2097). The impacts of other pesticides 
including atrazine, chlorpyrifos, and permethrin on glochidia and 
juvenile life stages have also recently been studied (Bringolf et al. 
2007b, p. 2101). This study determined that chlorpyrifos was toxic to 
both L. siliquoidea glochidia and juveniles (Bringolf et al. 2007b, p. 
2104). The above results indicate the potential toxicity of commonly 
applied pesticides and the threat to mussel species as a result of the 
widespread use of these pesticides. All of these pesticides are 
commonly used throughout the range of the sheepnose and spectaclecase.
    A potential, but undocumented, threat to freshwater mussel species, 
including sheepnose and spectaclecase, are contaminants referred to as 
``emerging contaminants'' that are being detected in aquatic ecosystems 
at an increasing rate. Pharmaceuticals, hormones, and other organic 
contaminants have been detected downstream from urban areas and 
livestock production (Kolpin et al. 2002, p. 1202). A large potential 
source of these emerging contaminants is wastewater being discharged 
through both permitted (National Pollutant Discharge Elimination 
System, or NPDES) and non-permitted sites

[[Page 3412]]

throughout the country. Permitted discharge sites are ubiquitous in 
watersheds with sheepnose and spectaclecase populations, providing 
ample opportunities for contaminants to impact the species (for 
example, there are more than 250 NPDES sites in the Meramec River, 
Missouri system, which harbors large, but declining, populations of 
sheepnose and spectaclecase; Roberts and Bruenderman 2000, p. 78).
    The information presented in this section represents some of the 
threats from chemical contaminants that have been documented both in 
the laboratory and field and demonstrates that chemical contaminants 
pose a substantial threat to sheepnose and spectaclecase. This 
information indicates the potential for contaminants from spills that 
are immediately lethal to species, to chronic contaminant exposure, 
which results in death, reduced growth, or reduced reproduction of 
sheepnose and spectaclecase to contribute to declining sheepnose and 
spectaclecase populations.
Summary of Factor A
    The decline of the freshwater mussels in the eastern United States 
is primarily the result of the long-lasting effects of habitat 
alterations such as impoundments, channelization, chemical 
contaminants, mining, oil and gas development, and sedimentation. 
Although efforts have been made to restore habitat in some areas, the 
long-term effects of large-scale and wide-ranging habitat modification, 
destruction, and curtailment will continue into the foreseeable future.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The spectaclecase and sheepnose are not commercially valuable 
species but may be increasingly sought by collectors as they become 
rarer. Although scientific collecting is not thought to represent a 
significant threat, unregulated collecting could adversely affect 
localized spectaclecase and sheepnose populations.
    Mussel harvest is illegal in some States (for example, Indiana and 
Ohio), but regulated in others (for example, Alabama, Kentucky, 
Tennessee, and Wisconsin). These species may be inadvertently harvested 
by inexperienced commercial harvesters unfamiliar with species 
identification. Although illegal harvest of protected mussel beds 
occurs (Watters and Dunn 1995, p. 225, 247-250), commercial harvest is 
not known to have a significant impact on the spectaclecase and 
    On the basis of this analysis, we find that overutilization for 
commercial, recreational, scientific, or educational purposes is not 
now a threat to the spectaclecase or sheepnose in any portion of its 
range or likely to become a significant threat in the foreseeable 

C. Disease or Predation

    Little is known about diseases in freshwater mussels (Grizzle & 
Brunner 2007, p. 6). However, mussel die-offs have been documented in 
spectaclecase and sheepnose streams (Neves 1986, p. 9), and some 
researchers believe that disease may be a factor contributing to the 
die-offs (Buchanan 1986, p. 53; Neves 1986, p. 11). Mussel parasites 
include water mites, trematodes, oligochaetes, leeches, copepods, 
bacteria, and protozoa (Grizzle & Brunner 2007, p. 4). Generally, 
parasites are not suspected of being a major limiting factor (Oesch 
1984, p. 6), but a recent study provides contrary evidence. 
Reproductive output and physiological condition were negatively 
correlated with mite and trematode abundance, respectively (Gangloff et 
al. 2008, pp. 28-30). Stressors that reduce fitness may make mussels 
more susceptible to parasites (Butler 2007, p. 90). Furthermore, 
nonnative mussels may carry diseases and parasites that are potentially 
devastating to the native mussel fauna, including spectaclecase and 
sheepnose (Strayer 1999, p. 88).
    The muskrat (Ondatra zibethicus) is cited as the most prevalent 
mussel predator (Convey et al. 1989, p. 654-655; Hanson et al. 1989, 
pp. 15-16; Kunz 1898, p. 328). Muskrat predation may limit the recovery 
potential of endangered mussels or contribute to local extirpations of 
previously stressed populations, according to Neves and Odom (1989, p. 
940), but they consider it primarily a seasonal or localized threat. 
B[ouml]pple and Coker (1912, p. 9) noted the occurrence of ``large 
piles of shells made by the muskrats'' on an island in the Clinch 
River, Tennessee, composed of ``about one-third'' spectaclecase shells. 
Predation by muskrats may be a seasonal and localized threat to 
spectaclecase and sheepnose populations but is probably not a 
significant threat rangewide.
    Some species of fish feed on mussels (for example, common carp 
(Cyprinus carpio), freshwater drum (Aplodinotus grunniens), redear 
sunfish (Lepomis microlophus)) and potentially on this species when 
young. Various invertebrates, such as flatworms, hydra, non-biting 
midge larvae, dragonfly larvae, and crayfish, may feed on juvenile 
mussels (Neves 2008, pers. comm.). Although predation by naturally 
occurring predators is a normal aspect of the population dynamics of a 
healthy mussel population, predation may amplify declines in small 
populations of this species. In addition, the potential now exists for 
the black carp (Mylopharyngodon piceus), a mollusk-eating Asian fish 
recently introduced into the waters of the United States (Strayer 1999, 
p. 89), to eventually disperse throughout the range of the 
spectaclecase and sheepnose.
    The life cycle of freshwater mussels is intimately related to that 
of the freshwater fish they use as hosts for their parasitic glochidia. 
For this reason, diseases that impact populations of freshwater fishes 
also pose a significant threat to mussels. Viral hemorrhagic septicemia 
(VHS) disease has been confirmed from much of the Great Lakes and St. 
Lawrence River system. In June 2008, muskellunge (Esox masquinongy) 
from Clearfork Reservoir, near Mansfield, Ohio, tested positive for 
carrying VHS virus. This is the first known occurrence of VHS virus in 
the Mississippi River basin.
    The VHS virus has been implicated as a mortality factor in fish 
kills throughout the Great Lakes region. It has been confirmed in 28 
fish species, but no identified hosts for sheepnose are on the U.S. 
Department of Agriculture's Animal and Plant Health Inspection Service 
(APHIS) list of fish species susceptible to VHS (APHIS 2008, pp. 1-2). 
Since the host for spectaclecase is unknown, we do not know how VHS 
could affect reproduction for spectaclecase. If the VHS virus 
successfully migrates out of the Clearfork Reservoir and into the Ohio 
River, it could spread rapidly and cause fish kills throughout the 
Mississippi River basin. Few spectaclecase and sheepnose populations 
are currently recruiting at sustainable levels, and fish kills could 
further reduce encounters with hosts and potentially reduce 
    In summary, disease in freshwater mollusks is poorly known and not 
currently considered a threat. Although there is no direct evidence at 
this time that predation is detrimentally affecting the spectaclecase 
or sheepnose, their small populations and limited ranges leaves them 
vulnerable to threats of predation from natural or introduced 
predators. Therefore, we conclude that predation currently represents a 
threat of low magnitude, but it could potentially become a significant 
future threat to the spectaclecase and

[[Page 3413]]

sheepnose due to their small population sizes.

D. The Inadequacy of Existing Regulatory Mechanisms

    States with extant spectaclecase and sheepnose populations prohibit 
the taking of mussels for scientific purposes without a State 
collecting permit. However, enforcement of this permit requirement is 
    The level of protection that spectaclecase and sheepnose receive 
from State listing varies from State to State. The sheepnose is State-
listed in every State that keeps such a list. Collection of sheepnose 
in Pennsylvania for use as fish bait is limited to 50 individuals per 
day. The spectaclecase is State-listed in 8 of the 10 States that 
harbor extant populations. Only in Missouri and Tennessee is the 
spectaclecase not assigned conservation status and West Virginia does 
not have any State-specific legislation similar to the Act.
    Nonpoint source pollution is considered a primary threat to 
sheepnose and spectaclecase habitat; however, current laws do not 
adequately protect spectaclecase and sheepnose habitat from nonpoint 
source pollution, as the laws to prevent sediment entering water ways 
are poorly enforced. Best management practices for sediment and erosion 
control are often recommended or required by local ordinances for 
construction projects; however, compliance, monitoring, and enforcement 
of these recommendations are often poorly implemented. Furthermore, 
there are currently no requirements within the scope of Federal 
environmental laws to specifically consider the spectaclecase and 
sheepnose during Federal activities.
    Point source discharges within the range of the spectaclecase and 
sheepnose have been reduced since the inception of the Clean Water Act 
(33 U.S.C. 1251 et seq.), but this may not provide adequate protection 
for filter feeding organisms that can be impacted by extremely low 
levels of contaminants (see ``Chemical Contaminants'' discussion under 
Factor A). There is no specific information on the sensitivity of the 
spectaclecase and sheepnose to common industrial and municipal 
pollutants, and very little information on other freshwater mussels. 
Therefore, it appears that a lack of adequate research and data 
prevents existing regulations, such as the Clean Water Act 
(administered by the EPA and the Corps), from being fully used or 
    The U.S. Army Corps of Engineers retains oversight authority and 
requires a permit for gravel-mining activities that deposit fill into 
streams under section 404 of the Clean Water Act. Additionally, a Corps 
permit is required under section 10 of the Rivers and Harbors Act (33 
U.S.C. 401 et seq.) for navigable waterways including the lower 50 
miles (80 km) of the Meramec River. However, many gravel-mining 
operations do not fall under these two categories.
    Despite these existing regulatory mechanisms, the spectaclecase and 
sheepnose continue to decline due to the effects of habitat 
destruction, poor water quality, contaminants, and other factors. We 
find that these regulatory measures have been insufficient to 
significantly reduce or remove the threats to the spectaclecase and 
sheepnose, and therefore that the inadequacy of existing regulatory 
mechanisms is a threat to these species throughout all of their ranges.
    Based on our analysis of the best available information, we have no 
reason to believe that the aforementioned regulations will offer 
adequate protection to the spectaclecase and sheepnose in the 
foreseeable future.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    Natural temperature regimes can be altered by impoundments, water 
releases from dams, industrial and municipal effluents, and changes in 
riparian habitat. Critical thermal limits for survival and normal 
functioning of many freshwater mussel species are unknown. High 
temperatures can reduce dissolved oxygen concentrations in the water, 
which slows growth, reduces glycogen stores, impairs respiration, and 
may inhibit reproduction (Fuller 1974, pp. 240-241). Low temperatures 
can significantly delay or prevent metamorphosis (Watters & O'Dee 1999, 
pp. 454-455). Water temperature increases have been documented to 
shorten the period of glochidial encystment, reduce righting speed, 
increase oxygen consumption, and slow burrowing and movement responses 
(Bartsch et al. 2000, p. 237; Fuller 1974, pp. 240-241; Schwalb & Pusch 
2007, pp. 264-265; Watters et al. 2001, p. 546). Several studies have 
documented the influence of temperature on the timing of aspects of 
mussel reproduction (for example, Allen et al. 2007, p. 85; Gray et al. 
2002, p. 156; Steingraeber et al. 2007, pp. 303-309). Peak glochidial 
releases are associated with water temperature thresholds that can be 
thermal minimums or thermal maximums, depending on the species (Watters 
& O'Dee 2000, p. 136). Abnormal temperature changes may cause 
particular problems to mussels whose reproductive cycles may be linked 
to fish reproductive cycles (for example,Young & Williams 1984).
Climate Change
    It is a widely accepted fact that changes in climate are occurring 
worldwide (IPCC 2007, p. 30). Understanding the effects of climate 
change on freshwater mussels is of crucial importance, because the 
extreme fragmentation of freshwater drainage systems, coupled with the 
limited ability of mussels to migrate, will make it particularly 
difficult for mussels to adjust their range in response to changes in 
climate (Strayer 2008, p. 30). For example, changes in temperature and 
precipitation can increase the likelihood of flooding or increase 
drought duration and intensity, resulting in direct impacts to 
freshwater mussels (Golladay et al. 2004, p. 503; Hastie et al. 2003, 
pp. 40-43). Indirect effects of climate change may include declines in 
host fish stocks, sea level rise, habitat reduction, and changes in 
human activity in response to climate change (Hastie et al. 2003, pp. 
Population Fragmentation and Isolation
    Most of the remaining spectaclecase and sheepnose populations are 
small and isolated and thus are susceptible to genetic drift, 
inbreeding depression, and random or chance changes to the environment, 
such as toxic chemical spills (Avise and Hamrick 1996, pp. 463-466; 
Smith 1990, pp. 311-321; Watters and Dunn 1995, pp. 257-258 Inbreeding 
depression can result in death, decreased fertility, smaller body size, 
loss of vigor, reduced fitness, and various chromosome abnormalities 
(Smith 1990, pp. 311-321). Despite any evolutionary adaptations for 
rarity, habitat loss and degradation increase a species' vulnerability 
to extinction (Noss and Cooperrider 1994, pp. 58-62). Numerous authors 
(including Noss and Cooperrider 1994, pp. 58-62; Thomas 1994, p. 373) 
have indicated that the probability of extinction increases with 
decreasing habitat availability. Although changes in the environment 
may cause populations to fluctuate naturally, small and low-density 
populations are more likely to fluctuate below a minimum viable 
population (the minimum or threshold number of individuals needed in a 
population to persist in a viable state for a given interval) (Gilpin 
and Soule 1986, pp. 25-33; Shaffer 1981, p. 131; Shaffer and Samson 
1985, pp. 148-150).

[[Page 3414]]

    These species were widespread throughout much of the upper two-
thirds of the Mississippi River system, for example, when few natural 
barriers existed to prevent migration (via host species) among suitable 
habitats. Construction of dams, however, destroyed many spectaclecase 
and sheepnose populations and isolated others. Recruitment reduction or 
failure is a potential problem for many small sheepnose populations 
rangewide, a potential condition exacerbated by its reduced range and 
increasingly isolated populations. If these trends continue, further 
significant declines in total sheepnose population size and consequent 
reduction in long-term survivability may soon become apparent.
    Spectaclecase are long-lived (up to 70 years; Havlik 1994, p. 19) 
while sheepnose are relatively long-lived (approximately 30 years; 
Watters et al. 2009, p. 221) Therefore, it may take decades for non-
reproducing populations of both species to become extinct following 
their isolation by, for example, the construction of a dam. The 
occasional discovery of relatively young spectaclecase in river reaches 
between impoundments indicates that some post-impoundment recruitment 
has occurred. The level of recruitment in these cases, however, appears 
to be insufficient to ensure the long-term sustainability of the 
spectaclecase. Small isolated populations of spectaclecase and 
sheepnose that may now be comprised predominantly of adult specimens 
could be dying out slowly in the absence of recruitment, even without 
other threats described above. Isolated populations usually face other 
threats that result in continually decreasing patches of suitable 
    Genetic considerations for managing imperiled mussels and for 
captive propagation were reviewed by Neves (1997a, p. 1422) and Jones 
et al. (2006, pp. 527-535), respectively. The likelihood is high that 
some populations of the spectaclecase and sheepnose are below the 
effective population size (EPS) (Soule 1980, pp. 162-164) necessary to 
adapt to environmental change and persist in the long term. Isolated 
populations eventually die out when population size drops below the EPS 
or threshold level of sustainability. Evidence of recruitment in many 
populations of these two species is scant, making recruitment reduction 
or outright failure suspect. These populations may be experiencing the 
bottleneck effect of not attaining the effective population size. 
Small, isolated, below effective population size-threshold populations 
of short-lived species (most host fishes) theoretically die out within 
a decade or so, while below-threshold populations of long-lived 
species, such as the spectaclecase and sheepnose, might take decades to 
die out even given years of total recruitment failure. Without 
historical barriers to genetic interchange, small, isolated populations 
could be slowly expiring, a phenomenon termed the extinction debt 
(Tilman et al. 1994, pp. 65-66). Even given the totally improbable 
absence of anthropogenic threats, we may lose disjunct populations to 
below-threshold effective population size. However, evidence indicates 
that general degradation continues to decrease habitat patch size and 
to act insidiously in the decline of spectaclecase and sheepnose 
    Spectaclecase and sheepnose mussels' scarcity and decreased 
population size makes maintaining adequate heterogeneity problematic 
for resource managers. Neves (1997b, p. 6) warned that ``[i]f we let 
conservation genetics become the goal rather than the guidelines for 
restoring and recovering mussel populations, then we will be doomed to 
failure with rare species.'' Habitat alteration, not lack of genetic 
variability, is the driving force of population extirpation (Caro and 
Laurenson 1994, pp. 485-486; Neves et al. 1997, p. 60). Nevertheless, 
genetics issues should be considered in maintaining high levels of 
heterozygosity during spectaclecase recovery efforts. Treating disjunct 
occurrences of this wide-ranging species as a metapopulation would 
facilitate conservation management while increasing recovery options 
(for example, translocating adults or introducing infested hosts and 
propagated juveniles) to establish and maintain viable populations 
(Neves 1997b, p. 6). Due to small population size and probable 
reduction of genetic diversity within populations, efforts should be 
made to maximize genetic heterogeneity to avoid both inbreeding 
(Templeton & Read 1984, p. 189) and outbreeding depression (Avise & 
Hamrick 1996, pp. 463-466) whenever feasible in propagation and 
translocation efforts (Jones et al. 2006, p. 529).
    We find that fragmentation and isolation of small remaining 
populations of the spectaclecase and sheepnose are current and ongoing 
threats to both species throughout all of their ranges that will 
continue into the foreseeable future. Further, stochastic events may 
play a magnified role in population extirpation when small, isolated 
populations are involved.
Exotic Species
    Various exotic or nonnative species of aquatic organisms are firmly 
established in the range of the spectaclecase and sheepnose. The exotic 
species that poses the most significant threat to the spectaclecase and 
sheepnose is the zebra mussel (Dreissena polymorpha). Its invasion of 
freshwater habitats in the United States poses a threat to mussel 
faunas in many regions, and species' extinctions are expected as a 
result of its continued spread in the eastern United States (Ricciardi 
et al. 1998, p. 615). Strayer (1999, pp. 75-80) reviewed in detail the 
mechanisms in which zebra mussels impact native mussels. The primary 
means of impact is direct fouling of the shells of live native mussels. 
Zebra mussels attach in large numbers to the shells of live native 
mussels and are implicated in the loss of entire native mussel beds. 
Fouling impacts include impeding locomotion (both laterally and 
vertically), interfering with normal valve movements, deforming valve 
margins, and locally depleting food resources and increasing waste 
products. Heavy infestations of zebra mussels on native mussels may 
overly stress the animals by reducing their energy stores. They may 
also reduce food concentrations to levels too low to support 
reproduction, or even survival in extreme cases.
    Other ways zebra mussels may impact spectaclecase and sheepnose is 
through filtering their sperm and possibly glochidia from the water 
column, thus reducing reproductive potential. Habitat for native 
mussels may also be degraded by large deposits of zebra mussel 
pseudofeces (undigested waste material passed out of the incurrent 
siphon) (Vaughan 1997, p. 11). Because spectaclecase are found in pools 
and zebra mussel veligers (larvae) attach to hard substrates at the 
point at which they settle out from the water column, spectaclecase are 
particularly vulnerable to zebra mussel invasion. The spectaclecase's 
colonial tendency could allow for very large numbers to be affected by 
a single favorable year for zebra mussels.
    Zebra mussels are established throughout the upper Mississippi, 
lower St. Croix, Ohio, and Tennessee Rivers, overlapping much of the 
current range of the spectaclecase and sheepnose. The greatest 
potential for present zebra mussel impacts to the spectaclecase and 
sheepnose appears to be in the upper Mississippi River. Kelner and 
Davis (2002, p. ii) stated that zebra mussels in the Mississippi River 
from Mississippi River Pool 4 downstream are ``extremely abundant and 
are decimating the native

[[Page 3415]]

mussel communities.'' Huge numbers of dead and live zebra mussels cover 
the bottom of the river in some localities up to 1 to 2 inches (2.5 to 
5.1 centimeters (cm)) deep (Havlik 2001a, p. 16), where they have 
reduced significantly the quality of the habitat with their pseudofeces 
(Fraley 2008, pers. comm.). Zebra mussels likely have reduced 
spectaclecase and sheepnose populations in these heavily infested 
    As zebra mussels may maintain high densities in big rivers, large 
tributaries, and below infested reservoirs, spectaclecase and sheepnose 
populations in affected areas may be significantly impacted. For 
example, zebra mussel densities in the Tennessee River remained low 
until 2002, but are now abundant enough below Wilson Dam to be measured 
quantitatively (Garner 2008, pers. comm.). In addition, there is long-
term potential for zebra mussel invasions into other systems that 
currently harbor spectaclecase and sheepnose populations. Zebra mussels 
occur in the lower St. Croix River, one of the strongholds for 
spectaclecase, although it is unclear whether they are likely to spread 
much further upstream due to the transition from lake-like conditions 
to almost exclusively riverine conditions above RM 25.
    The Asian clam (Corbicula fluminea) has spread throughout the range 
of the spectaclecase and sheepnose since its introduction in the mid-
1900s. Asian clams compete with native mussels, especially juveniles, 
for food, nutrients, and space (Leff et al. 1990, p. 415; Neves & 
Widlak 1987, p. 6) and may ingest unionid sperm, glochidia, and newly 
metamorphosed juveniles of native mussels (Strayer 1999, p. 82; Yeager 
et al. 2000, p. 255). Dense Asian clam populations actively disturb 
sediments that may reduce habitat for juveniles of native mussels 
(Strayer 1999, p. 82).
    Asian clam densities vary widely in the absence of native mussels 
or in patches with sparse mussel concentrations, but Asian clam density 
is never high in dense mussel beds, indicating that the clam is unable 
to successfully invade small-scale habitat patches with high unionid 
biomass (Vaughn & Spooner 2006, pp. 334-335). The invading clam 
therefore appears to preferentially invade sites where mussels are 
already in decline (Strayer 1999, pp. 82-83; Vaughn & Spooner 2006, pp. 
332-336) and does not appear be a causative factor in the decline of 
mussels in dense beds. However, an Asian clam population that thrives 
in previously stressed, sparse mussel populations might exacerbate 
unionid imperilment through competition and impeding mussel population 
expansion (Vaughn & Spooner 2006, pp. 335-336).
    A molluscivore (mollusk eater), the black carp (Mylopharyngodon 
piceus) is a potential threat to native mussels (Strayer 1999, p. 89); 
it has been introduced into North America since the 1970s. The species 
has been proposed for widespread use by aquaculturists to control 
snails, the intermediate host of a trematode (flatworm) parasite that 
affects catfish in commercial culture ponds in the southeast and lower 
Midwest. Black carp are known to eat clams (Corbicula spp.) and unionid 
mussels in China, in addition to snails. They are the largest of the 
Asian carp species, reaching more than 4 ft. in length and achieving a 
weight in excess of 150 pounds (Nico & Williams 1996, p. 6). Foraging 
rates for a 4-year-old fish average 3 or 4 pounds (1.4-1.8 kg) a day, 
indicating that a single individual could consume 10 tons (9,072 kg) of 
native mollusks over its lifetime (MICRA 2005, p. 1). In 1994, 30 black 
carp escaped from an aquaculture facility in Missouri during a flood. 
Other escapes into the wild by non-sterile black carp are likely to 
    The round goby (Neogobius melanostomus) is another exotic fish 
species released into the Great Lakes that is well established and 
likely to spread through the Mississippi River system (Strayer 1999, 
pp. 87-88). This species is an aggressive competitor of similar sized 
benthic fishes (sculpins, darters), as well as a voracious carnivore, 
despite its size (less than 10 in. (25.4 cm) in length), preying on a 
variety of foods, including small mussels and fishes that could serve 
as glochidial hosts (Janssen and Jude 2001, p. 325; Strayer 1999, p. 
88). Round gobies may therefore have important indirect effects on the 
spectaclecase and sheepnose through negative effects to their hosts.
    Additional exotic species will invariably become established in the 
foreseeable future (Strayer 1999, pp. 88-89). Added to potential direct 
threats, exotic species could carry diseases and parasites that may be 
devastating to the native biota. Because of our ignorance of mollusk 
diseases and parasites, ``it is imprudent to conclude that alien 
diseases and parasites are unimportant'' (Strayer 1999, p. 88).
    Exotic species, such as those described above, are an ongoing 
threat to the spectaclecase and sheepnose--a threat that is likely to 
increase as these exotic species expand their occupancy within the 
ranges of the spectaclecase and sheepnose.

Summary of Threats

    The decline of the spectaclecase and sheepnose in the eastern 
United States (described by Butler 2002a, entire; Butler 2002b, entire) 
is primarily the result of habitat loss and degradation (Neves 1991, p. 
252). These losses have been well documented since the mid-19th century 
(Higgins 1858, p. 550). Chief among the causes of decline are 
impoundments, channelization, chemical contaminants, mining, and 
sedimentation (Neves 1991, p. 252; Neves 1993, pp. 4-6; Neves et al. 
1997, pp. 60, 63-75; Watters 2000, pp. 262-267; Williams et al. 1993, 
pp. 7-9). These stressors have had profound impacts on sheepnose and 
spectaclecase populations and their habitat.
    The majority of the remaining populations of the spectaclecase and 
sheepnose are generally small and geographically isolated (Butler 
2002a, p. 27; 2002b, p. 27). The patchy distributional pattern of 
populations in short river reaches makes them much more susceptible to 
extirpation from single catastrophic events, such as toxic chemical 
spills (Watters and Dunn 1995, p. 257). Furthermore, this level of 
isolation makes natural repopulation of any extirpated population 
virtually impossible without human intervention. In addition, the fish 
host of spectaclecase is unknown; thus, propagation to reestablish the 
species in restored habitats and to maintain non-reproducing 
populations and focused conservation of its fish host are currently not 
possible. Although there are ongoing attempts to alleviate some of 
these threats at some locations, there appear to be no populations 
without significant threats, and many threats are without obvious or 
readily available solutions.
    Recruitment reduction or failure is a threat for many small 
spectaclecase and sheepnose populations rangewide, a condition 
exacerbated by reduced range and increasingly isolated populations 
(Butler 2002a, p. 28; 2002b, p. 28). If these trends continue, further 
significant declines in total spectaclecase and sheepnose population 
size and consequent reduction in long-term viability may soon become 
    Various exotic species of aquatic organisms are firmly established 
in the range of the spectaclecase and sheepnose. The exotic species 
that poses the most significant threat to the spectaclecase and 
sheepnose is the zebra mussel. The invasion of the zebra mussel poses a 
serious threat to mussel faunas in many regions, and species 
extinctions are expected as a result of its

[[Page 3416]]

continued spread in the eastern United States (Ricciardi et al. 1998, 
p. 618).

Proposed Determination

    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We find that the spectaclecase and 
sheepnose are presently in danger of extinction throughout their entire 
range, based on the immediacy, severity, and scope of the threats 
described under Factors A, D, and E, above. Although there are ongoing 
attempts to alleviate some threats, there appear to be no populations 
without current significant threats, and many threats are without 
obvious or readily available solutions. These isolated species have a 
limited ability to recolonize historically occupied stream and river 
reaches and are vulnerable to natural or human-caused changes in their 
stream and river habitats. Their range curtailment, small population 
size, and isolation make the spectaclecase and sheepnose more 
vulnerable to threats such as sedimentation, disturbance of riparian 
corridors, changes in channel morphology, point and nonpoint source 
pollutants, urbanization, and introduced species and to stochastic 
events (for example, chemical spills). Therefore, on the basis of the 
best available scientific and commercial information, we propose 
listing the spectaclecase and sheepnose as endangered in accordance 
with sections 3(6) and 4(a)(1) of the Act.
    Under the Act and our implementing regulations, a species may 
warrant listing if it is endangered or threatened throughout all or a 
significant portion of its range. Threats to the spectaclecase and 
sheepnose occur throughout their ranges; therefore, we assessed the 
status of the species throughout their entire ranges. The threats to 
the survival of the species occur throughout the species' ranges and 
are not restricted to any particular significant portion of those 
ranges. Accordingly, our assessment and proposed determination applies 
to both species throughout their entire ranges.

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
practices. Recognition through listing encourages and results in public 
awareness and conservation by Federal, State, and local agencies, 
private organizations, and individuals. The Act encourages cooperation 
with the States and requires that recovery actions be carried out for 
all listed species. The protection required of Federal agencies and the 
prohibitions against take and harm are discussed, in part, below.
    The primary purpose of the Act is the conservation of endangered 
and threatened species and the ecosystems upon which they depend. The 
ultimate goal of such conservation efforts is the recovery of these 
listed species, so that they no longer need the protective measures of 
the Act. Subsection 4(f) of the Act requires the Service to develop and 
implement recovery plans for the conservation of endangered and 
threatened species, unless such a plan will not promote the 
conservation of the species. The recovery planning process involves the 
identification of actions that are necessary to halt or reverse the 
species' decline by addressing the threats to its survival and 
recovery. The goal of this process is to restore listed species to a 
point where they are secure, self-sustaining, and functioning 
components of their ecosystems.
    Recovery planning includes the development of a recovery outline 
shortly after a species is listed, preparation of a draft and final 
recovery plan, and revisions to the plan as significant new information 
becomes available. The recovery outline guides the immediate 
implementation of urgent recovery actions and describes the process to 
be used to develop a recovery plan. The recovery plan identifies site-
specific management actions that will achieve recovery of the species, 
measurable criteria that determine when a species may be downlisted or 
delisted, and methods for monitoring recovery progress. Recovery plans 
also establish a framework for agencies to coordinate their recovery 
efforts and provide estimates of the cost of implementing recovery 
tasks. Recovery teams (comprised of species experts, Federal and State 
agencies, non-government organizations, and stakeholders) are often 
established to develop recovery plans. When completed, the recovery 
outline, draft recovery plan, and the final recovery plan will be 
available on our Web site (http://www.fws.gov/endangered), or from our 
Rock Island, Illinois, Ecological Services Field Office (see FOR 
    Implementation of recovery actions generally requires the 
participation of a broad range of partners, including other Federal 
agencies, States, Tribal, nongovernmental organizations, businesses, 
and private landowners. Examples of recovery actions include habitat 
restoration (e.g., restoration of native vegetation), research, captive 
propagation and reintroduction, and outreach and education. The 
recovery of many listed species cannot be accomplished solely on 
Federal lands because their range may occur primarily or solely on non-
Federal lands. To achieve recovery of these species requires 
cooperative conservation efforts on private, State, and Tribal lands.
    Listing will also require the Service to review any actions on 
Federal lands and activities under Federal jurisdiction that may 
adversely affect the two species; allow State plans to be developed 
under section 6 of the Act; encourage scientific investigations of 
efforts to enhance the propagation or survival of the animals under 
section 10(a)(1)(A) of the Act; and promote habitat conservation plans 
on non-Federal lands and activities under section 10(a)(1)(B) of the 
    Section 7(a) of the Act, as amended, requires Federal agencies to 
evaluate their actions with respect to any species that is proposed or 
listed as endangered or threatened and with respect to its critical 
habitat, if any is designated. Regulations implementing this 
interagency cooperation provision of the Act are codified at 50 CFR 
part 402. Federal agencies are required to confer with us informally on 
any action that is likely to jeopardize the continued existence of a 
proposed species. Section 7(a)(4) requires Federal agencies to confer 
with the Service on any action that is likely to jeopardize the 
continued existence of a species proposed for listing or result in 
destruction or adverse modification of proposed critical habitat. If a 
species is listed subsequently, section 7(a)(2) requires Federal 
agencies to ensure that activities they authorize, fund, or carry out 
are not likely to jeopardize the continued existence of the species or 
destroy or adversely modify its critical habitat. If a Federal action 
may adversely affect a listed species or its critical habitat, the 
responsible Federal agency must enter into formal consultation with the 
    Federal activities that may affect the sheepnose and spectaclecase 
include, but are not limited to, the funding of, carrying out of, or 
the issuance of permits for reservoir construction, natural gas 
extraction, stream alterations, discharges, wastewater facility 
development, water withdrawal projects, pesticide registration, mining, 
and road and bridge construction.

Jeopardy Standard

    Prior to and following listing and designation of critical habitat, 
if prudent

[[Page 3417]]

and determinable, the Service applies an analytical framework for 
jeopardy analyses that relies heavily on the importance of core area 
populations to the survival and recovery of the species. The section 
7(a)(2) analysis is focused not only on these populations but also on 
the habitat conditions necessary to support them.
    The jeopardy analysis usually expresses the survival and recovery 
needs of the species in a qualitative fashion without making 
distinctions between what is necessary for survival and what is 
necessary for recovery. Generally, if a proposed Federal action is 
incompatible with the viability of the affected core area 
population(s), inclusive of associated habitat conditions, a jeopardy 
finding is considered to be warranted, because of the relationship of 
each core area population to the survival and recovery of the species 
as a whole.

Section 9 Take

    Section 9(a)(2) of the Act, and its implementing regulations found 
at 50 CFR 17.21, set forth a series of general prohibitions and 
exceptions that apply to all endangered wildlife. These prohibitions, 
in part, make it illegal for any person subject to the jurisdiction of 
the United States to take (includes harass, harm, pursue, hunt, shoot, 
wound, kill, trap, or collect, or to attempt any of these), import or 
export, ship in interstate commerce in the course of commercial 
activity, or sell or offer for sale in interstate or foreign commerce 
any listed species. It also is illegal to knowingly possess, sell, 
deliver, carry, transport, or ship any wildlife that has been taken 
illegally. Certain exceptions apply to agents of the Service and State 
conservation agencies.
    We may issue permits to carry out otherwise prohibited activities 
involving endangered wildlife species under certain circumstances. 
Regulations governing permits are at 50 CFR 17.22 for endangered 
species. Such permits are available for scientific purposes, to enhance 
the propagation or survival of the species, or for incidental take in 
connection with otherwise lawful activities.
    Our policy, as published in the Federal Register on July 1, 1994 
(59 FR 34272), is to identify, to the maximum extent practicable, those 
activities that would or would not likely constitute a violation of 
section 9 of the Act. The intent of this policy is to increase public 
awareness as to the potential effects of this final listing on future 
and ongoing activities within a species' range. We believe that the 
following activities are unlikely to result in a violation of section 
    (1) Existing discharges into waters supporting these species, 
provided these activities are carried out in accordance with existing 
regulations and permit requirements (for example, activities subject to 
sections 402, 404, and 405 of the Clean Water Act and discharges 
regulated under the National Pollutant Discharge Elimination System).
    (2) Actions that may affect the spectaclecase or sheepnose and are 
authorized, funded, or carried out by a Federal agency when the action 
is conducted in accordance with any reasonable and prudent measures we 
have specified in accordance with section 7 of the Act.
    (3) Development and construction activities designed and 
implemented under Federal, State, and local water quality regulations 
and implemented using approved best management practices.
    (4) Existing recreational activities, such as swimming, wading, 
canoeing, and fishing, that are in accordance with State and local 
regulations, provided that if a spectaclecase or sheepnose is 
collected, it is immediately released, unharmed.
    Activities that we believe could potentially result in take of 
spectaclecase or sheepnose include but are not limited to:
    (1) Illegal collection or capture of the species;
    (2) Unlawful destruction or alteration of the species' occupied 
habitat (for example, unpermitted instream dredging, channelization, or 
discharge of fill material);
    (3) Violation of any discharge or water withdrawal permit within 
the species' occupied range; and
    (4) Illegal discharge or dumping of toxic chemicals or other 
pollutants into waters supporting spectaclecase or sheepnose.
    We will review other activities not identified above on a case-by-
case basis to determine whether they are likely to result in a 
violation of section 9 of the Act. We do not consider these lists to be 
exhaustive and provide them as information to the public.
    You should direct questions regarding whether specific activities 
may constitute a future violation of section 9 to the Field Supervisor 
of the Service's Rock Island, Illinois Ecological Services Field Office 
(see FOR FURTHER INFORMATION CONTACT section). You may request copies 
of the regulations regarding listed wildlife from and address questions 
about prohibitions and permits to the U.S. Fish and Wildlife Service, 
Ecological Services Division, Henry Whipple Federal Building, 1 Federal 
Drive, Fort Snelling, MN 55111 (Phone (612) 713-5350; Fax (612) 713-

Critical Habitat


    Critical habitat is defined in section 3 of the Act as:
    (i) The specific areas within the geographical area occupied by a 
species, at the time it is listed in accordance with the Act, on which 
are found those physical or biological features
    (I) Essential to the conservation of the species, and
    (II) That may require special management considerations or 
protection; and
    (ii) Specific areas outside the geographical area occupied by a 
species at the time it is listed, upon a determination that such areas 
are essential for the conservation of the species.
    Conservation is defined in section 3 of the Act as the use of all 
methods and procedures needed to bring the species to the point at 
which listing under the Act is no longer necessary.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against Federal agencies carrying out, funding, 
or authorizing the destruction or adverse modification of critical 
habitat. Section 7(a)(2) requires consultation on Federal actions that 
may affect critical habitat. The designation of critical habitat does 
not affect land ownership or establish a refuge, wilderness, reserve, 
preserve, or other conservation area. Such designation does not allow 
the government or public to access private lands. Such designation does 
not require implementation of restoration, recovery, or enhancement 
measures by non-Federal landowners. Where a landowner seeks or requests 
Federal agency funding or authorization for an action that may affect a 
listed species or critical habitat, the consultation requirements of 
section 7(a)(2) of the Act would apply, but even in the event of a 
destruction or adverse modification finding, the obligation of the 
Federal action agency and the applicant is not to restore or recover 
the species, but to implement reasonable and prudent alternatives to 
avoid destruction or adverse modification of critical habitat.

Prudency Determination

    Section 4(a)(3) of the Act, as amended, and implementing 
regulations (50 CFR 424.12), require that, to the maximum extent 
prudent and determinable, we designate critical

[[Page 3418]]

habitat at the time the species is determined to be endangered or 
threatened. Our regulations (50 CFR 424.12(a)(1)) state that the 
designation of critical habitat is not prudent when one or both of the 
following situations exist: (1) The species is threatened by taking or 
other human activity, and identification of critical habitat can be 
expected to increase the degree of threat to the species, or (2) such 
designation of critical habitat would not be beneficial to the species.
    There is currently no imminent threat of take attributed to 
collection or vandalism under Factor B (overutilization for commercial, 
recreational, scientific, or educational purposes) for sheepnose and 
spectaclecase and identification of critical habitat is not expected to 
initiate such a threat. In the absence of finding that the designation 
of critical habitat would increase threats to a species, if there are 
any benefits to a critical habitat designation, then a prudent finding 
is warranted. The potential benefits include: (1) Triggering 
consultation under section 7(a)(2) of the Act, in new areas for actions 
in which there may be a Federal nexus where it would not otherwise 
occur because the species may not be present; (2) focusing conservation 
activities on the most essential habitat features and areas; (3) 
increasing awareness of important habitat areas among State or county 
governments or private entities; and (4) preventing inadvertent harm to 
the species.
    Critical habitat designation includes the identification of the 
physical and biological features of the habitat essential to the 
conservation of each species that may require special management and 
protection. As such, these designations will provide useful information 
to individuals, local and State governments, and other entities engaged 
in activities or long-range planning that may affect areas essential to 
the conservation of the species. Conservation of the spectaclecase and 
sheepnose and essential features of their habitats will require habitat 
management, protection, and restoration, which will be facilitated by 
disseminating information on the locations and the key physical and 
biological features of those habitats. In the case of spectaclecase and 
sheepnose, these aspects of critical habitat designation would 
potentially benefit the conservation of the species. Therefore, since 
we have determined that the designation of critical habitat will not 
likely increase the degree of threat to these species and may provide 
some measure of benefit, we find that designation of critical habitat 
is prudent for the spectaclecase and sheepnose.

Primary Constituent Elements

    In accordance with sections 3(5)(A)(i) and 4(b)(1)(A) of the Act 
and regulations at 50 CFR 424.12, in determining which areas to propose 
as critical habitat, we must consider those physical and biological 
features--primary constituent elements in the necessary and appropriate 
quantity and spatial arrangement--essential to the conservation of the 
species. We must also consider those areas essential to the 
conservation of the species that are outside the geographical area 
occupied by the species. Primary constituent elements include, but are 
not limited to:
    (1) Space for individual and population growth and for normal 
    (2) Food, water, air, light, minerals, or other nutritional or 
physiological requirements;
    (3) Cover or shelter;
    (4) Sites for breeding, reproduction, and rearing (or development) 
of offspring; and
    (5) Habitats that are protected from disturbance or are 
representative of the historical, geographical, and ecological 
distribution of a species.
    We are currently unable to identify the primary constituent 
elements for spectaclecase and sheepnose because information on the 
physical and biological features that are considered essential to the 
conservation of these species is not known at this time. The apparent 
poor viability of the species' occurrences observed in recent years 
indicates that current conditions are not sufficient to meet the basic 
biological requirements of these species in many rivers. Since 
spectaclecase and sheepnose have not been observed for decades in many 
of their historical locations, and much of the habitat in which they 
still persists has been drastically altered, the optimal conditions 
that would provide the biological or ecological requisites of these 
species are not known. Although we can surmise that habitat degradation 
from a variety of factors has contributed to the decline of these 
species, we do not know specifically what essential physical or 
biological features of that habitat are currently lacking for 
spectaclecase and sheepnose.
    Key features of the basic life history, ecology, reproductive 
biology, and habitat requirements of most mussels, including 
spectaclecase and sheepnose, are unknown. Species-specific ecological 
requirements have not been determined (for example, minimum water flow 
and effects of particular pollutants). Population dynamics, such as 
species' interactions and community structure, population trends, and 
population size and age class structure necessary to maintain a long-
term viability, have not been determined for these species. Basics of 
reproductive biology for these species are unknown, such as age and 
size at earliest maturity, reproductive longevity, and the level of 
recruitment needed for species survival and long-term viability. Of 
particular concern to the spectaclecase is the lack of known host(s) 
species essential for glochidia survival and reproductive success. 
Similarly, although recent laboratory studies have produced successful 
transformation of sheepnose glochidia on a few fish species, many 
questions remain concerning the natural interactions between the 
sheepnose and its known hosts. Because the host(s) for spectaclecase is 
unknown and little is known about the sheepnose hosts, there is a 
degree of uncertainty at this time as to which specific areas might be 
essential to the conservation of these species (for example, the 
host(s)'s biological needs and population sizes necessary to support 
mussel reproduction and population viability) and thus meet a key 
aspect of the definition of critical habitat. As we are unable to 
identify many physical and biological features essential to the 
conservation of spectaclecase and sheepnose, we are unable to identify 
areas that contain these features. Therefore, although we have 
determined that the designation of critical habitat is prudent for 
spectaclecase and sheepnose, because the biological and physical 
requirements of these species are not sufficiently known, we find that 
critical habitat for spectaclecase and sheepnose is not determinable at 
this time.

Peer Review

    In accordance with our policy, ``Notice of Interagency Cooperative 
Policy for Peer Review in Endangered Species Act Activities,'' that was 
published on July 1, 1994 (59 FR 34270), we will seek the expert 
opinion of at least three appropriate independent specialists regarding 
this proposed rule. The purpose of such review is to ensure listing 
decisions are based on scientifically sound data, assumptions, and 
analysis. We will send copies of this proposed rule to the peer 
reviewers immediately following publication in the Federal Register. We 
will invite these peer reviewers to comment, during the public comment 
period, on the specific assumptions and the data that are the basis for 
our conclusions regarding the proposal to

[[Page 3419]]

list spectaclecase and sheepnose as endangered and our proposal 
regarding critical habitat for this species.

Required Determinations

Clarity of the Rule

    We are required by Executive Orders 12866 and 12988 and by the 
Presidential Memorandum of June 1, 1998, to write all rules in plain 
language. This means that each rule we publish must:
    (a) Be logically organized;
    (b) Use the active voice to address readers directly;
    (c) Use clear language rather than jargon;
    (d) Be divided into short sections and sentences; and
    (e) Use lists and tables wherever possible.
    If you feel that we have not met these requirements, send us 
comments by one of the methods listed in the ADDRESSES section. To 
better help us revise the rule, your comments should be as specific as 
possible. For example, you should tell us the names of the sections or 
paragraphs that are unclearly written, which sections or sentences are 
too long, the sections where you feel lists or tables would be useful, 

Executive Order 13211

    On May 18, 2001, the President issued Executive Order 13211 on 
regulations that significantly affect energy supply, distribution, and 
use. Executive Order 13211 requires agencies to prepare Statements of 
Energy Effects when undertaking certain actions. This rule is not 
expected to significantly affect energy supplies, distribution, or use. 
Therefore, this action is not a significant energy action, and no 
Statement of Energy Effects is required.

Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.)

    This proposed rule does not contain any new collections of 
information that require approval by the Office of Management and 
Budget (OMB) under the Paperwork Reduction Act. The rule would not 
impose new recordkeeping or reporting requirements on State or local 
governments, individuals, businesses, or organizations. We may not 
conduct or sponsor, and you are not required to respond to, a 
collection of information unless it displays a currently valid OMB 
control number.

National Environmental Policy Act

    We determined that we do not need to prepare an environmental 
assessment, as defined under the authority of the National 
Environmental Policy Act of 1969 (42 U.S.C. 4321 et seq.), in 
connection with regulations adopted under section 4(a) of the Act. We 
published a notice outlining our reasons for this determination in the 
Federal Register on October 25, 1983 (48 FR 49244).

References Cited

    A complete list of all references cited in this rule is available 
on the Internet at http://www.regulations.gov or upon request from the 
Field Supervisor, Rock Island, Illinois Ecological Services Field 


    The primary authors of this proposed rule are the staff members of 
the Service's Rock Island and Twin Cities Field Offices (see FOR 

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, Transportation.

Proposed Regulation Promulgation

    Accordingly, we propose to amend part 17, subchapter B of chapter 
I, title 50 of the Code of Feral Regulations, as follows:


    1. The authority citation for part 17 continues to read as follows:

    Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C. 
4201-4245; Pub. L. 99-625, 100 Stat. 3500; unless otherwise noted.

    2. In Sec.  17.11(h) add the entries for ``Sheepnose'' and 
``Spectaclecase'' in alphabetical order under CLAMS to the List of 
Endangered and Threatened Wildlife, as follows:

Sec.  17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

                        Species                                                     Vertebrate
--------------------------------------------------------                         population where                      When       Critical     Special
                                                           Historical range       endangered or         Status        listed      habitat       rules
           Common name                Scientific name                               threatened
                                                                      * * * * * * *
                                                                      * * * * * * *
Sheepnose........................  Plethobasus cyphyus.  U.S.A. (AL, IL, IN,   NA.................  E               ..........           NA           NA
                                                          IA, KY, MN, MS, MO,
                                                          OH, PA, TN, VA, WV,
                                                                      * * * * * * *
Spectaclecase                      Cumberlandia          U.S.A. (AL, AR, IL,   NA.................  E               ..........           NA           NA
                                    monodonta.            IN, IA, KS, KY, MN,
                                                          MO, NE, OH, TN, VA,
                                                          WV, WI).
                                                                      * * * * * * *

[[Page 3420]]

* * * * *

    Dated: December 16, 2010.
Rowan W. Gould,
Acting Director, U.S. Fish and Wildlife Service.
[FR Doc. 2011-469 Filed 1-18-11; 8:45 am]