[Federal Register: May 19, 2009 (Volume 74, Number 95)]
[Proposed Rules]
[Page 23376-23388]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr19my09-22]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS-R3-ES-2008-0030; 92210-1111-0000-FY09-B3]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition To List the Coaster Brook Trout as Endangered
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
12-month finding on a petition to list the coaster brook trout
(Salvelinus fontinalis) as endangered under the Endangered Species Act
of 1973, as amended (Act). The petition also asked that critical
habitat be designated for the species. After review of all available
scientific and commercial information, we find that the coaster brook
trout is not a listable entity under the Act, and therefore, listing is
not warranted. We ask the public to continue to submit to us any new
information that becomes available concerning the taxonomy, biology,
ecology, and status of coaster brook trout and to support cooperative
conservation of coaster brook trout within its historical range in the
Great Lakes.
DATES: The finding announced in this document was made on May 19, 2009.
ADDRESSES: This finding is available on the Internet at http://
www.regulations.gov at Docket Number [FWS-R3-ES-2008-0030]. Supporting
documentation for this finding is available for inspection, by
appointment, during normal business hours at the U.S. Fish and Wildlife
Service, Region 3 Fish and Wildlife Service Regional Office, 1 Federal
Drive, Bishop Henry Whipple Federal Building, Fort Snelling, MN 55111.
Please submit any new information, materials, comments, or questions
concerning this finding to the above address, Attention: Coaster brook
trout.
FOR FURTHER INFORMATION CONTACT: Jessica Hogrefe, Region 3 Fish and
Wildlife Service Regional Office (see ADDRESSES) (telephone 612-713-
5346; facsimile 612-713-5292). Persons who use a telecommunications
device for the deaf (TDD) may call the Federal Information Relay
Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.) requires
that, for any petition to revise the Lists of Endangered and Threatened
Wildlife and Plants that contains substantial scientific and commercial
information that listing may be warranted, we make a finding within 12
months of the date of our receipt of the petition on whether the
petitioned action is: (a) Not warranted, (b) warranted, or (c)
warranted, but the immediate proposal of a regulation implementing the
petitioned action is precluded by other pending proposals to determine
whether species are threatened or endangered, and expeditious progress
is being made to add or remove qualified species from the List of
Endangered and Threatened Species. Section 4(b)(3)(C) of the Act
requires that we treat a petition for which the requested action is
found to be warranted but precluded as though resubmitted on the date
of such finding, that is, requiring that we make a subsequent finding
within 12 months. Such 12-month findings must be published in the
Federal Register. This notice constitutes our 12-month finding for the
petition to list the U.S. population of coaster brook trout.
Previous Federal Action
The Sierra Club Mackinac Chapter, Huron Mountain Club, and Marvin
J. Roberson filed a petition, dated February 22, 2006, with the
Secretary of the Interior to list as endangered the ``naturally
spawning anadromous (lake-run) coaster brook trout throughout its known
historic range in the conterminous United States'' and to designate
critical habitat under the Act. The petition clearly identified itself
as such and included the requisite identification information for the
petitioners, as required in 50 CFR 424.14(a). On behalf of the
petitioners, Peter Kryn Dykema, Secretary of the Huron Mountain Club,
submitted supplemental information, dated May 23, 2006, in support of
the original petition. This supplemental information provided further
information on the species' status and biology, particularly for brook
trout in the Salmon Trout River.
On September 13, 2007, we received a 60-day notice of intent to sue
over the Service's failure to determine, within 1 year of receiving the
petition, whether the coaster brook trout warrants listing. Under
section 4 of the Act, the Service is to make a finding, to the maximum
extent practicable within 90 days of receiving a petition, that it does
or does not present substantial scientific or commercial information
indicating that the petitioned action may be warranted. Further, the
Act requires that, within 12 months of receiving a petition found to
present substantial information, the Service must determine whether the
petitioned action is warranted. A complaint was filed in U.S. District
Court in the District of Columbia on December 17, 2007, for failure to
make a timely finding (Sierra Club, et al. v. Kempthorne, No. 1:07-cv-
02261 (D.D.C. December 17, 2007)). The Service reached a negotiated
settlement with the plaintiffs to submit the 90-day finding to the
Federal Register by March 15, 2008. We published a ``substantial'' 90-
day finding March 20, 2008. The negotiated settlement further required
the Service to publish the 12-month finding in the Federal Register by
December 15, 2008. The deadline for the 12-month finding was extended
to April 15, 2009, by mutual consent. On April 15, 2009, we filed an
unopposed motion to extend the deadline for the coaster brook trout 12-
month finding to May 12, 2009.
Species Information
Species Description
Brook trout (Salvelinus fontinalis), also called brook char or
speckled trout, is one of three species in the genus Salvelinus (chars)
native to north and eastern North America; the others being lake trout
(S. namaycush) and Arctic char (S. alpinus). The chars are a sub-group
of fishes in the salmon and trout subfamily (Salmoninae) that is
distinct from the ``true'' trout and salmon sub-groups.
The brook trout throughout its range in eastern North America
exhibits considerable variation in growth rate, color, and other
features, but generally can be distinguished from other char and trout
species by its olive-green to dark brown back with a light yellow-brown
vermiculate pattern, sides with large yellow-brown spots and blue halos
surrounding small, sporadic red and orange spots. Pectoral, pelvic,
anal, and lower caudal fin have leading edges of white bordered by
black with the
[[Page 23377]]
remainder predominantly reddish to orange. Sea-run brook trout become
silver with purple iridescence and show red spots on the sides (Scott
and Crossman 1973, p. 208).
Distribution
The historical range of native brook trout extends along Hudson Bay
in Canada across the Provinces of Manitoba, Ontario and Quebec, to
Newfoundland and Labrador and south to Nova Scotia and New Brunswick in
Canada; and from eastern Iowa through northern Illinois, northern Ohio,
and the Great Lakes drainage (Minnesota, Michigan, Wisconsin), through
the New England States (New York, New Hampshire, Vermont, Maine,
Massachusetts, Pennsylvania, New Jersey), large New England rivers
(such as the Hudson River and Connecticut River), and through the
Appalachian Mountains in Maryland, Virginia, West Virginia, North
Carolina, South Carolina, Tennessee, south to Georgia (MacCrimmon and
Campbell 1969, pp. 1700-1702; MacCrimmon et al. 1971, p. 452; Scott and
Crossman 1973, pp. 209-210; Power 1980, p. 142). Naturalized
populations of brook trout were established as early as the late 1800s
beyond the historical native range by introductions to waters in
western North America, South America, Eurasia, Africa, and New Zealand
(MacCrimmon and Campbell 1969, p. 1699, pp. 1703-1717). The current
range of native brook trout still extends through Canada and down to
Georgia in the U.S., but in many locations, populations have been
completely extirpated or have contracted within this range towards
upper stream reaches, higher altitudes, or headwaters (EBJV 2006, p.
2).
Distribution of Brook Trout in the Great Lakes
According to Bailey and Smith (1981, p. 1549) and MacCrimmon and
Campbell (1969, p. 1701), brook trout are native to the lakes and
tributaries of Lakes Superior, Huron, Michigan, and the tributaries of
Lakes Erie and Ontario. Brook trout are not believed to have been
present in Minnesota streams above barrier falls to Lake Superior
(Smith and Moyle 1944, p. 119) or throughout most of the lower
peninsula of Michigan (MIDNR 2008a, pp. 1-2; MacCrimmon and Campbell
1969, p. 1704).
Habitat Requirements
Brook trout require clear, cold, well-oxygenated water to thrive.
They are generally found in water ranging between 41-68[deg] Fahrenheit
(5-20[deg] Celsius), with their likely preferred temperature falling
near the middle of this range (Power 1980, p. 172). Thermal
requirements within this range vary by life cycle phase and season
(Scott and Crossman 1973, p. 211; Blanchfield and Ridgway 1997, p. 750;
Baril and Magnan 2002, pp. 177-178).
The brook trout spawns in late summer or autumn, the date varying
with latitude and temperature. Spawning takes place most often over
gravel beds but may be successfully accomplished over a variety of
substrates if there is spring upwelling or a moderate current (Scott
and Crossman 1973, p. 210). Power (1980, p. 151) describes rangewide
brook trout spawning, which occurs in the fall, when day length and
temperature are decreasing. In northerly regions and at high
elevations, brook trout may spawn as early as late August and spawning
may be delayed until December in southern areas. As is typical for
salmonids, females prepare redds (hollows scooped out for spawning) in
suitable gravel substrate. The female then deposits her eggs in the
redd where they are fertilized by a male. After spawning there is no
further parental involvement with the young. The redd protects the eggs
and allows an adequate exchange of dissolved gases and other materials
during development.
Brook trout are carnivorous, feeding opportunistically upon a
variety of prey, such as worms, leeches, crustaceans, aquatic insects,
terrestrial insects, spiders, mollusks, and fish (Scott and Crossman
1973, p. 212). Anadromous (migrating from salt water to spawn in fresh
water) forms vary their feeding behavior and prey items based on their
age and the environment, marine or riverine, they are occupying (Newman
and Dubois 1997, p. 9). Brook trout also show diverse foraging
behaviors; some individuals may be sedentary, eating crustaceans from
the lower portion of the water column, whereas others in the same
system may be more active and eat insects from the upper portion of the
water column (McLaughlin et al. 1999, p. 386). This resource
polymorphism may play a supplementary role in the extensive adaptive
radiation (evolution of ecological variability within a rapidly
multiplying lineage; Smith and Sk[uacute]lason 1996) observed in this
species.
Genetics of Brook Trout
A large amount of genetic variation for brook trout is
distributed among populations (large Fst values). This pattern is
heavily influenced by the diverse ecological and life-history
characteristics of brook trout populations (population connectivity
or isolation, philopatric tendency). This pattern of highly
differentiated populations of brook trout is found at small and
large geographic scales. Population genetic structuring is common in
brook trout throughout its range (Angers et al. 1999, pp. 1049-
1050). Like many salmonids, brook trout tend to have a hierarchical
population structure resulting from the hierarchical design of the
networks of streams and lake or coastal areas in which they live,
and a complicated life cycle that leads to strong local adaptations.
Taxonomic resolution can be even more complicated at the lake level
when lakes include sympatric (occupying the same or overlapping
geographic area without interbreeding) but genetically divergent
brook trout populations such as in Lake Mistassini in Canada (Fraser
and Bernatchez 2008, p. 1197). This degree of genetic divergence
that forms among populations is reflective of the reproductive
connections (isolation) among the populations across the range of
the taxon.
Six distinct genetic mitochondrial (mtDNA) clades have been
identified throughout the range of brook trout in eastern North America
(Danzmann et al. 1998, p. 1307). These mtDNA clades reflect historical
isolation in glacial refugia or long periods of isolation in nonglacial
areas in the southern part of the species' range. The Wisconsin glacial
advance which covered portions of Canada covered all five Great Lakes
15,000 years ago (Bailey and Smith 1981, p. 1543). As these glaciers
receded, brook trout recolonized the lakes from the Mississippi and
Atlantic refugia (Danzmann et al. 1998, pp. 1308, 1312). Given this
pattern of glaciation, genetic diversity is greatest at the southern
portion of the species' range and gradually decreases northward
(Danzmann et al. 1998, pp. 1310-1311). As the most geographically
isolated (for tens of thousands of years), brook trout in the southern
part of the species' range (along the Appalachian Mountains south to
Georgia) are the most diverse, containing all six mtDNA clades. The
Great Lakes contains three of the six mtDNA clades. Throughout the
northern portion of their range in Canada, brook trout are the least
genetically diverse, with only a single mtDNA clade present. Within
each of these lineages, there is evidence to suggest that selection is
driving rapid phenotypic divergence in some populations.
Results based on microsatellite DNA variation identified nine
distinct genetic assemblages of brook trout in the U.S. (King 2009,
unpub. data). Assemblages from the nonglacial southern part of the
species' range (along the Appalachian Mountains from Pennsylvania to
Georgia) in the U.S. are the most genetically divergent, and this
divergence among the assemblages generally decreases as the range
progresses northward.
[[Page 23378]]
Genetics of Brook Trout in the Great Lakes
Populations from Lake Superior and tributaries to Lake Erie form
two of the nine genetic assemblages of brook trout in the U.S. The Lake
Erie populations are the most divergent assemblage from the northern
part of the species' range. Lake Superior populations are similar in
the degree of genetic divergence to the remaining northern assemblages
grouping with the average genetic distance between brook trout
populations in the U.S. Samples from the rest of the Great Lakes were
not available for analysis. Although brook trout in the Great Lakes do
not contain any wholly unique mtDNA clades, they do contain a large
amount of the genetic variation in a confined portion of the range
(Danzmann et al. 1998, pp. 1310-1311).
Native populations of brook trout in Lake Superior in most cases
have retained their native genetic characteristics despite the stocking
of hatchery fish from sources outside and within the Lake Superior
basin. In Lake Superior, the intensity and purpose of stocking has
varied over time and space. For example, Minnesota tributaries to Lake
Superior have been stocked with hatchery strains that originated from
outside of the Great Lakes Basin to provide fishing opportunities above
fish passage barriers (Wilson et al. 2008, p. 1312). Until the early
1990s, most of the stocked fish in Lake Superior were domesticated
strains from outside the Great Lakes basin (Schreiner et al. 2008, p.
1357), although many stocking events were undocumented and records of
early stocking events are incomplete (Wilson et al. 2008, p. 1312).
These stocking efforts were not targeted at rehabilitation and from
that perspective, results were poor. The stocked fish were not
behaviorally or evolutionarily adapted to the environment in which they
were planted, criteria known to limit survival and reproductive success
(Schreiner et al. 2008, p. 1357). Burnham-Curtis (2001, p. 2) concluded
that hatchery fish have had little reproductive success in Lake
Superior streams based on her examination of 36 tributaries to Lake
Superior and 9 hatchery stocks outplanted into the lake. However, the
genetic methods used by Burnham-Curtis provided low power to detect
genetic introgression of hatchery fish into native populations (Wilson
et al. 2008, p. 1312). A recent study by D'Amelio and Wilson (2008, p.
1215) used genetic methods with high power to detect genetic
introgression of hatchery fish into natural populations. This study
documented only low levels of genetic introgression of Lake Nipigon
hatchery fish into native populations of brook trout from six
tributaries to Lake Superior's Nipigon Bay (D'Amelio and Wilson 2008,
p. 1222), despite decades of stocking. A study by Scribner et al.
(2006, pp. 3-4) examined nine brook trout populations from Lake
Superior tributaries on the south shore of Michigan and four hatchery
strains outplanted into those tributaries. This study used similar
methods to D'Amelio and Wilson (2008). Scribner et al. (2006, p. 8)
concluded that hatchery stocking appears to have minimal if any impact
of on brook trout.
Brook Trout Life-History Diversity
An individual's ability to produce multiple phenotypes (visible or
observable characteristics) in response to its environment is termed
phenotypic plasticity (Scheiner 1993, p. 36). Recent studies have
recognized the role of phenotypic plasticity as a major source of
phenotypic variation in natural populations (Price et al. 2003, p.
1438). The brook trout exhibits remarkable phenotypic plasticity across
its natural range. This plasticity allows it to thrive in a variety of
environments, from cold subarctic regions, through temperate zones and
in southern refugia in eastern North America, and in a range of places
where it has been introduced (Power 1980, p. 142). Although primarily a
stream-dwelling species, brook trout also occupy inland lakes and
coastal waters. Because of the variety of the freshwater, estuary, and
ocean environments, migratory plasticity is also favored. The brook
trout's dispersal subsequent to receding glaciation, and separation
into isolated breeding stocks in diverse habitats subject to an array
of natural and man-made influences have all contributed to this
variability (Power 1980, p. 142).
Brook trout display considerable life-history variation throughout
their native range (Huckins and Baker 2008, p. 1229). Brook trout
across its range exhibit a variety of life-history types (polymorphisms
or ecotypes), including fluvial (stream-dwelling), adfluvial (migrating
between lakes and streams), lacustrine (lake-dwelling), and anadromous
(migrating from salt water to spawn in fresh water) forms.
Understanding life-history diversity in a species requires knowledge of
the evolutionary history, ecological setting, and reproductive
relationships among ecotypes. Reproductive interactions between
ecotypes are reflected by the magnitude and pattern of genetic
differentiation observed between life-history phenotypes at neutral
genetic markers. The expression of migratory behavior (expressed as the
adfluvial and anadromous ecotypes) by any individual fish will be
partially in direct response to its environment. Phenotypic expression
of more than one form may be expected in a population located in a
variable environment containing habitats for several ecotypes. The
amount of phenotypic plasticity a population will exhibit for the
migratory trait also has a heritable genetic basis and will be
determined by the intensity and type of selective pressures that
population experiences (Via and Lande 1985, pp. 517-519; Theriault et
al. 2008, pp. 418-419).
Adoption of migratory adfluvial form or stream-resident life-
history form in brook trout has been modeled under a conditional
strategy framework where environmentally influenced threshold traits
determine which ecotype a fish will adopt (Hendry et al. 2004, pp. 124-
125). Growth rate efficiencies, body size, and concentration of
juvenile hormone have all been identified as potential threshold traits
(Theriault and Dodson 2003, pp. 1155-1157). Theoretical work by Ridgway
(2008, p. 1185) and Uller (2008, pp. 436-437) also provide information
to suggest parental effects are important to the expression of
alternate ecotypes of brook trout. These parental effects describe an
affect of the parental phenotype on the offspring's phenotype such as
coaster females producing larger eggs and spawning in different
locations from stream-resident ecotypes, influencing the habitat use
(Morinville and Rasmussen 2006, pp. 701-702) and growth rate at the
juvenile stage (Perry et al. 2005, p. 1358). These differences in
growth rate and habitat use impact potential threshold traits.
Work on sympatric brook trout life forms at young ages largely
comes from a few studies on anadromous populations. Morinville and
Rasmussen (2003) studied the bioenergetics of young brook trout
exhibiting anadromous migratory and stream-resident life tactics. They
found that the anadromous migrants have higher metabolic costs and had
consumption rates 1.4 times that of stream residents but growth
efficiencies of the anadromous form were lower than that of residents.
Spatial utilization of habitat differed among the life tactics as well,
with migratory individuals occupying faster-flowing waters compared to
the resident fish which used pool areas (p. 408). They concluded that
migrant brook trout have noticeably different energy budgets than
resident brook trout from the same system (p. 406). Morinville and
Rasmussen (2008) also investigated morphological differences between
life
[[Page 23379]]
tactics. The authors concluded that migrant brook trout were found to
be more streamlined (narrower and shallower bodies) than resident brook
trout, and these differences persisted into the marine life of the
migrant fish (pp. 175, 183). The differences were powerful enough to
derive discriminant functions using five of the measured traits
allowing for accurate classification of juvenile brook trout as either
migrant or resident with an overall correct classification rate of 87
percent.
A study by Theriault et al. (2007b, p. 61) found that sympatric
anadromous and fluvial brook trout in the Sainte-Marguerite River in
Quebec belonged to a single gene pool. Phenotypic plasticity is,
therefore, a major force driving the expression of these two life
histories from this population. Evolution of phenotypic plasticity in
this population was influenced by mating systems with most of the
mating between different morphotypes occurring between fluvial males
and anadromous females. Additional work in this system demonstrated
significant heritability for life-history tactic and for body size
(Theriault et al. 2007a, pp. 7-8) indicating expression of life-history
tactic in this population can be effected by natural or artificial
selection.
Life-History Diversity in Great Lakes Brook Trout
Fish that complete their life cycle exclusively in tributaries to
the Great Lakes exhibit the fluvial life history and are defined as
stream residents. ``Coaster'' (the subject of the petition) is a
regional term for a life-history variant of brook trout in the Great
Lakes (Burnham-Curtis 2001, p. 2; Wilson et al. 2008, p. 1) which use
lake waters of the Great Lakes for all or a portion of its life cycle
(Becker 1983, p. 320). The coaster form can be further divided into an
adfluvial ecotype that migrates from the stream to the lake and back
into tributaries to spawn and a lacustrine ecotype that completes its
life cycle entirely within the lake (Huckins et al. 2008, p. 1323). In
the Great Lakes region, spawning usually occurs from mid-September
through mid-November. Distinct life histories associated with the
coaster and stream-resident types result in different physical,
demographic, and ecological characteristics for the forms (Huckins et
al. 2008, p. 1337; Huckins and Baker 2008, p. 1241; Ridgway 2008, p.
1185). Specifically, coasters tend to live longer than stream residents
(5-8 years versus less than 5 years), reach maturation later (females
at 2-4 years versus 1-2 years), attain larger length and weight as
adults (12-25 inches and 0.75-8 pounds (30-64 centimeters (cm) and 341-
3632 grams (g)) versus (5-15 inches (13-38 cm) and (less than 1 pound
(<454 g), be more fecund (1500-3000 eggs per female versus 100-1500
eggs per female), and move greater distances (up to 19-217 miles (30-
350 kilometers (km)) versus less than 19 miles (30 km)) (Scott and
Crossman 1973, pp. 208, 210, 211; Power 1980, p. 157; Becker 1983, pp.
318, 320; Ritchie and Black 1988, pp. 19, 50, 51; Quinlan 1999, pp. 11,
12, 14, 16, 17, 20; Swainson 2001, pp. 40, 41, 60, 64; WIDNR and USFWS
2005, p. 16; Huckins and Baker 2008, pp. 1239, 1241; Huckins et al.
2008, pp. 1328, 1329, 1337; Mucha and Mackereth 2008, p. 1210; Schram
2008a, pers. comm.; Chase 2008, pers. comm.).
Coasters have been historically documented in Lakes Superior,
Huron, and Michigan brook trout populations (Bailey and Smith 1981, p.
1549; Dehring and Krueger 1985, p. 1; Enterline 2000, p. 1; MIDNR
2008a, pp. 1-2). However, Lake Superior is the only Great Lake with
extant coaster forms of brook trout, and all available literature is
from this area. Coasters in the Great Lakes are found in Canada and the
U.S. in substantially fewer locations than they were historically
(Newman et al. 2003, p. 39). Populations in the Great Lakes basin with
these life-history forms are documented within Canada in tributaries to
Nipigon and Black Bays, the Nipigon River, Lake Nipigon and the Pancake
River in the eastern part of Lake Superior (Newman et al. 2003, p. 39;
Chase and Swainson 2009, pers. comm.). Within the U.S. portion of the
Great Lakes basin, populations that express the coaster form occur in
Isle Royale National Park in Tobin Harbor, Big and Little Siskiwit
Rivers, and Washington Creek as well as on the south shore of Lake
Superior in the Salmon Trout River (Newman et al. 2003, p. 39).
As previously stated, brook trout populations within the upper
Great Lakes exhibit fluvial, adfluvial, and lacustrine life-history
forms, coasters comprising the latter two forms. Populations of brook
trout in Lake Superior likely function as types of metapopulations,
with the coaster life forms serving as dispersers (D'Amelio and Wilson
2008, p. 1222; Sloss et al. 2008, p. 1249). The viability of a
metapopulation is strongly contingent upon maintaining dispersal among
populations. Although brook trout exhibit spawning site fidelity,
individuals exhibiting the adfluvial life forms in Lake Superior have
also been shown to stray or disperse among streams (D'Amelio and Wilson
2008, p. 1222; Mucha and Mackereth, p. 1211). The long-term persistence
of a metapopulation requires a balance between local extinction and
recolonization of constituent populations (see Hanski 1998 for a review
of metapopulations). Dispersing individuals offset local population
extinction by providing a means for recolonization (Brown and Kodric-
Brown 1977, p. 448; Reeves et al. 1995, p. 340). Dispersing individuals
also provide for gene flow among discrete populations, countering
losses of genetic fitness while still allowing the development and
distribution of unique adaptive traits (Ingvarsson 2001, p. 63; Tallmon
et al. 2004, p. 494). Thus, the coaster life-history forms are
important to the long-term viability of brook trout populations
throughout Lake Superior.
Genetic studies of stream-resident (fluvial life form) brook trout
show substantial genetic structuring among populations in Michigan,
Wisconsin, Minnesota, and Canada characterized by distinct regional
groupings or metapopulations (Burnham-Curtis 1996, pp. 10-11; Burnham-
Curtis 2001, p. 10; Sloss et al. 2008, p. 1249; Wilson et al. 2008, p.
1312; Scribner et al. 2008, p. 9). In studies aimed at determining
genetic differences between the coaster polymorphism and stream-
resident fish occupying tributaries connected to the lake, molecular
genetic work in Lake Superior indicates that coasters and stream-
resident brook trout occupying tributaries to the first barrier are
parts of the same population (D'Amelio and Wilson. 2008, p. 1221;
Scribner et al. 2008, p. 9; Stott 2008, p. 5). Work investigating the
genetic differences of various tributaries to the lake found distinct
differences among populations of brook trout in each tributary to Lake
Superior (Burnham-Curtis 1996, p. 10; Burnham-Curtis 2000, p. 7;
Burnham-Curtis 2001, p. 10; D'Amelio and Wilson 2008, p. 1222; Sloss et
al. 2008, p. 1249; Scribner et al. 2008, p. 9). Within Lake Superior,
regional genetic differences are evident between brook trout
populations in Nipigon Bay, Isle Royale, and Lake Nipigon-Grand Portage
(Wilson et al. 2008, p. 1313). Adfluvial brook trout are thought to be
the mechanism providing genetic communication among these regional
aggregations and straying of a coaster was documented in Nipigon Bay
and at Isle Royale (D'Amelio et al. 2008, p. 1347; Stott 2008, p. 4).
Sloss et al. (2008) investigated genetic differentiation among four
Wisconsin populations of stream-resident brook trout. His work found
significant differentiation among populations to the point the authors
observed that for these populations,
[[Page 23380]]
there appears to be a near complete lack of gene flow among them
resulting in genetic drift (Sloss et al. 2008, p. 1249). None of these
isolated populations are thought to currently have adfluvial ecotypes
as part of the population. This observation is consistent with the
contemporary lack of an adfluvial form that historically provided the
regional genetic connection for the three metapopulations previously
mentioned.
As characterized in the entire brook trout species, phenotypic
plasticity and adaptive radiation (Schluter 2000, p. 1) appear to
represent the continuum of evolutionary processes underlying the
expression of life-history variation in populations of brook trout in
Lake Superior (Ardren 2008, pp. 1-2). As stated above, plastic
responses allow individuals to obtain high fitness in new environments.
Alternatively, adaptive genetic differentiation among populations may
provide evolutionary advantages. First, there are fitness costs to
being highly plastic. For example, plastic genotypes need to maintain
sensory and developmental pathways in order to induce plastic responses
that are not required by nonplastic genotypes (Relyea 2002, pp. 272-
273). Secondly, if the plastic response to a new environment is
insufficient and directional selection favors an extreme phenotype,
there will be genetic evolution of the trait (adaptive radiation).
Therefore, if a population of brook trout experiences divergent
selection in stable environments, we would expect the ecotypes to
evolve genetic differences and nonplastic forms because the cost of
maintaining the phenotypic plasticity would be too high. Findings in
the Salmon Trout River indicate phenotypic plasticity plays a major
role in the expression of the adfluvial and fluvial ecotypes while
information from Isle Royale indicates adaptive radiation has occurred
separating adfluvial and lacustrine coaster ecotypes. Migratory
plasticity could be favored in situations where adfluvial and stream-
resident brook trout co-occur because the environments they occupy are
highly variable (Huckins et al. 2008, p. 1324; Ridgway 2008, pp. 1186-
1187). The alternating selection patterns associated with these diverse
and variable environments create a fitness advantage for plastic
genotypes over nonplastic genotypes. In addition, the metapopulation
structure mediated by coaster brook trout (D'Amelio and Wilson 2008, p.
1222; Ridgway 2008, p. 1181) favors plasticity over adaptive genetic
differences among populations because dispersal among populations
increases environmental heterogeneity and favors an increase in trait
reaction norm (the pattern of visible characteristics produced by a
given genetic makeup of an organism under different environmental
conditions; Sultan and Spencer 2002, p. 281). Alternatively, the
adfluvial and lacustrine ecotypes on Isle Royale are physically
isolated and in this situation, adaptive radiation would be favored
over the evolution of phenotypic plasticity (Price 2003, pp. 1437-
1438).
If phenotypic plasticity is the source of differences observed
between stream-resident and brook trout, then these ecotypes are
expressed in a single population and represent the extremes of the
reaction norm for migratory behavior. Scribner et al. (2008, p. 10) did
not observe genetic differences between sympatric adfluvial brook trout
and presumed stream-resident ecotypes in the Salmon Trout River on the
south shore of Lake Superior. Analysis of microsatellite DNA provided
high statistical power to detect genetic differences between ecotypes.
In fact, the authors did observe highly significant genetic differences
between brook trout sampled above and below the impassable waterfall in
this system. In addition, when collections from the Salmon Trout River
were compared with native brook trout populations sampled from 10 other
nearby tributaries, the lowest pairwise measure of genetic distinction
was observed between the resident and adfluvial ecotypes sampled below
the waterfall in the Salmon Trout River. D'Amelio and Wilson (2008, p.
1221) used similar methods to document that adfluvial brook trout in
the Nipigon Bay were not genetically distinct from presumed resident
brook trout sampled from tributaries to the bay. These findings in the
Salmon Trout River and the Nipigon Bay area indicate phenotypic
plasticity likely plays a major role in the expression of the adfluvial
and fluvial ecotypes.
Theriault et al. (2008, pp. 417-419) used an eco-genetic model to
demonstrate that intensive harvest of anadromous fish reduces the
probability of migration in brook trout over the course of 100 years.
This study provides a basic framework for understanding how fisheries-
induced selection (mortality from fishing) influences the evolution of
alternate life-history tactics that are expressed by phenotypic
plasticity. For example, directional selection imposed by fishing-
induced mortality on coaster brook trout confers high fitness to the
survivors of the fishery but not necessarily with respect to natural
selection. There is also uncertainty regarding the rate of recovery for
expression of the adfluvial form after fishing selection is reduced or
eliminated because there is not automatically equal directional
selection in the opposite direction for expression of the adfluvial
form. In the case of the coaster, habitat degradation and competition
from nonnative salmon may exclude brook trout from habitats that would
allow juvenile brook trout to achieve growth rates necessary to express
the adfluvial coaster ecotype (Huckins et al. 2008, pp. 1337-1339).
Additionally, metapopulation structure mediated by coaster brook trout
(D'Amelio et al. 2008, p. 1348) favors plasticity over adaptive genetic
differences among populations (Sultan and Spencer 2002, p. 281). Loss
of coasters in most populations in Lake Superior has reduced migration
among populations (Sloss et al. 2008, p. 1249) resulting in a reduction
in environmental heterogeneity favoring a decrease in the reaction norm
of traits. These studies demonstrate that human-induced selective
forces can alter the reaction norm for a population which can result in
the loss of plasticity needed to express the coaster life-history
forms.
Brook trout experts contend that if environmental conditions are
suitable (i.e., threats are abated), the adfluvial life form of brook
trout populations in Lake Superior can be readily reconstituted from
purely resident stock (USFWS 2009, p. 8); this is believed unlikely for
other salmonids (e.g., Oncorhynchus mykiss). This assertion is
predicated on three premises. First, adult brook trout of one ecotype
may produce offspring of the other ecotype. For example, two resident
fish could breed and produce offspring that exhibit both the adfluvial
and fluvial life-history strategies. Further, stream-resident and
adfluvial ecotypes from the same population interbreed. This means that
within a stream, individuals that exhibit the resident and adfluvial
forms reside within and are drawn from the same population. Second, the
chars (genus Salvelinus), including brook trout, show greater
phenotypic plasticity than most other salmonids. Adfluvial brook trout
do not require substantial physiological changes (for example,
smoltification) to successfully migrate and survive in the lake
environment. Thus, the fitness costs to maintain the genetic code for
plasticity are likely less relative to saltwater-dwelling salmonids.
Hence, it is reasonable to expect a brook trout population will
maintain the ability (genetic code) to express the full array of life
forms over time. Third, life-history strategy for
[[Page 23381]]
brook trout is strongly controlled by environmental conditions or
triggers. As such, the experts believe that, provided the necessary
environmental conditions or triggers exist, life forms can be expressed
even if temporally lost from a population.
Current Population Status of Brook Trout
The current range of native brook trout remains generally
unchanged, extending through much of eastern North America, from
eastern Canada, south through the Great Lakes and northeast to Georgia
in the U.S. However, populations throughout this range have experienced
significant declines. The current range of native brook trout started
diminishing over the past 200 years as a result of ecosystem disruption
following European settlement of North America (Newman and DuBois
1997). Habitat destruction by forestry, agricultural practices,
industrial water use, dams, and pollution were responsible for this
decline (Power 1980, p. 141). Brook trout were once present in nearly
every coldwater stream and river in the eastern U.S. and Canada, but
populations began to disappear as early agriculture, timber, and
textile practices and industries cleared the region's protective
forests and degraded the streams with sediment and pollution (Power
1980, p. 141; EBJV 2006, p. 1).
Throughout much of their natural range, remaining stream
populations have retreated into extreme headwater, high elevation, or
upstream reaches (EBJV 2006, p. 2). In the eastern U.S., healthy stream
populations of brook trout (wild brook trout occupying 90-100 percent
of their historical habitat) exist in only 5 percent of subwatersheds
(EBJV 2006, p. 2). Anadromous stocks along the U.S. coast and in many
Canadian rivers have been decimated by dams and estuarine pollution
(Power 1980, p. 195). In the southern portion of its range (southern
Appalachian Mountains), brook trout populations have declined by 75
percent, persisting now only in isolated headwater reaches (EBJV 2006,
p. 6).
Various threats are persistent across the brook trout range. Most
of them involve habitat loss and degradation, such as poor land
management, high water temperature, sedimentation (roads),
urbanization, degraded riparian habitat, stream fragmentation (roads),
dam inundation/fragmentation, and forestry practices (EBJV 2006, pp. 3,
5). Poor land management associated with agriculture (such as clearing
streamside vegetation, over-grazing sensitive areas, ineffectively
managing nutrients, and ditching small streams) ranks as the most
widely distributed impact to brook trout across the eastern U.S. (EBJV
2006, p. 2). Climate change presents a significant threat to brook
trout, with some southern portions predicted to lose between 53-97
percent of their brook trout habitat due to high water temperatures
(Flebbe 2006, p. 1379). While some uncertainty remains about the exact
temperature increase that will result from climate change, the present
range of brook trout is predicted to shrink, particularly in the
southern Appalachians (Hudy et al. 2005, p. 5). Nonnative species are
now present throughout most of the range (Parsons 1973, p. 5).
Interactions with these nonnatives are considered to be among the most
significant biological threats to brook trout rangewide (Peck 2001,
p.13; Hudy et al. 2005, p. 3; EBJV 2006, pp. 2-3, 5). Brown trout have
been shown to displace or reduce stream populations of brook trout
throughout their natural range (Nyman 1970, p. 348; Fausch and White
1981, p. 1226; Waters 1983, p. 144). Encroachment by rainbow trout has
also been documented in the contraction of the range of native brook
trout across their native range (Kelly et al., 1980, pp. 9-10; Power
1980, p. 195; Larson and Moore 1985, p. 200). Species such as small
mouth bass and yellow perch are considered to be significant
competitors with lake-dwelling brook trout (EBJV 2006, pp. 22, 28, 34).
Current Population Status of Brook Trout in the Upper Great Lakes
Brook trout populations throughout the upper Great Lakes region are
relatively common and geographically widespread, although distribution
and abundance is much reduced from historical levels (Power 1980, p.
195; Becker 1983, pp. 321-322; WIDNR and USFWS 2005, p. 17). Dramatic
declines in abundance and distribution of both coaster and stream-
resident ecotypes of brook trout occurred in the upper Great Lakes from
the 1850s to mid-1900s (Goodier 1982, pp. 110, 112; Ritchie and Black
1988, p. 15; Newman and Dubois 1997, pp. 4-6; Enterline 2000, p. 1;
WIDNR and USFWS 2005, pp. 17-18; Schreiner et al. 2008, p. 1305;
Schreiner et al. 2008, p. 1351; Huckins et al. 2008, p. 1322).
There are presently at least 200 streams with documented brook
trout populations in the upper Great Lakes (Moore and Bream 1965, p.
19; Goodier 1982, p. 110; Enterline 2000, p. 30; Newman et al. 2003,
pp. 31-37; Quinlan 2004, unpub. data; Bassett 2009, unpub. data; Ward
2007, p. 16; Schram 2008b, pers. comm.; Scott 2008, pers. comm.; Chase
2009, pers. comm.; OMNR 2009, unpub. data). The current specific status
of most of these populations is not known, but they are described by
the Michigan, Minnesota, and Wisconsin natural resource agencies as
stable and self-sustaining in the upper Great Lakes (Holtz 2008, p. 2;
MIDNR 2008a, p. 49; Schreiner and Ebbers 2008, pers. comm.).
In coldwater tributaries to the upper Great Lakes, brook trout were
historically distributed from the river mouth upstream to the
headwaters or to impassible barriers (Smith and Moyle 1944, p. 119;
Moore and Braem 1965, p. 19; Goodier 1982, p. 111; Becker 1983, p. 321;
WIDNR and USFWS 2005). The brook trout numbers in these stream reaches
once numbered in the hundreds to thousands (Huckins and Baker 2008, p.
1231). A 30-year data set from Wisconsin tributaries shows that, in
streams historically occupied solely by brook trout, brook trout have
contracted into upstream sections and are now nearly absent in lower
reaches (WIDNR 2008, unpub. data). Brook trout abundance has declined
despite the persistence of suitable conditions for brook trout and high
numbers of juvenile nonnative salmonids (WIDNR 2008, unpub. data). In
Wisconsin tributaries to Lake Superior, the distribution of stream-
resident brook trout populations has declined by nearly 50 percent from
historical levels (WIDNR and USFWS 2005, p. 17).
Historically, 119 tributaries to Lake Superior and purportedly 6
Lake Huron streams supported populations of brook trout with coaster
ecotypes (Newman et al. 2003, pp. 31-38; Enterline 2000, p. 30). Once
abundant and widespread throughout the northern portions of the Great
Lakes, populations of brook trout that still exhibit the coaster
ecotypes are presently limited to a few locations (Dehring and Krueger
1985, p. 1; Bailey and Smith 1981, p. 1549; Goodyear et al. 1982, pp.
63-65; Enterline 2000, p. 30; Newman et al. 2003, p. 39; Schreiner et
al. 2008, p. 1351; Mucha and Mackereth 2008, p. 1). Although self-
sustaining populations of stream-resident brook trout are currently
present in 56 of 58 U.S. streams and in all 61 Canadian streams
identified in the Brook Trout Rehabilitation Plan for Lake Superior as
historically supporting populations with coaster ecotypes (Newman et
al. 2003, pp. 31-37; Quinlan 2008, unpub. data; Schreiner 2008, pers.
comm.; Schram 2008c, pers. comm.; Scott 2008, pers. comm.; Chase 2009,
pers. comm.), only 18 populations with coaster ecotypes still persist
there (15 stream-spawning-adfluvial, and 3 lake-spawning-lacustrine)
(Goodyear 1982, pp. 63-65; Quinlan 1999, p. 19; Ritchie and Black
[[Page 23382]]
1988, p. 15; Swainson 2001, p. 41; Newman et al. 2003, pp. 28-39;
Enterline 2000, p. 30; Chase 2009, pers. comm.).
Over the last decade, the presence of coaster brook trout has been
confirmed in other locations within the upper Great Lakes. Surveys, and
in some cases genetic analysis, have confirmed the presence of brook
trout with coaster ecotypes in the following locations; Minnesota
tributaries to Lake Superior (Newman et al. 1999, p. 2; Burnham-Curtis
2000, p. 4; Pranckus and Ostazeski 2003, p. 5; Ward 2007, p. 16), three
Michigan tributaries to Lake Superior (Stimmel 2006, p. 56; MIDNR
2008a, p. 2; Leonard 2009, pers. comm.), along the shoreline of the Red
Cliff Indian Reservation, Wisconsin (Stott and Quinlan 2008, p. 21),
and in Little Todd Harbor and Rock Harbor, Isle Royale (Gorman et al.
2008, p. 1257). The origin of these fish is unknown and natural
reproduction of fish exhibiting the coaster ecotype has not been
confirmed, therefore these locations are not identified as supporting
self-sustaining populations. However, they have potential to be self-
sustaining populations, as outlined by Schreiner et al. (2008).
Abundance of individuals in populations exhibiting the coaster
ecotypes is stable or increasing in several regions of Lake Superior.
In the Salmon Trout River, Michigan, abundance as determined by video
surveillance increased from 118 to 243 in the period from 2004 to 2006
(MIDNR 2008a, p. 6). In the Nipigon River, angler catch per hour has
increased from the late 1980s to the present, while harvest has
decreased substantially (Houle 2004, p. 13). In South Bay, Lake
Nipigon, estimates of spawner abundance continue to increase and
currently number about 600 fish--up from fewer than 100 in the recent
past, but still fewer than the estimated 2,500 present in the mid-1900s
(Swainson 2009, pers. comm.). In Tobin Harbor, Isle Royale National
Park, Michigan, estimates of adult brook trout from 1996, 2001, and
2008 has remained around 200-250 fish (USFWS unpublished data).
Relative abundance based on shoreline electrofishing index surveys in
Tobin Harbor from 1997 to 2008 has fluctuated from 0.3 per hour to 16.7
per hour (USFWS 2008, unpub. data).
There are reintroduction stocking efforts ongoing in several
streams on the Grand Portage Indian Reservation (Newman and Johnson
1996, p. 4), Red Cliff Indian Reservation, Keweenaw Bay Indian
Community Reservation (Donofrio 2002, p. 1), and in Whittlesey Creek,
Wisconsin (USFWS and WIDNR 2003, p. 5). Supplementation stocking
occurred in Siskiwit Bay, Isle Royale, from 1999 to 2005. Data
collected to date indicates limited success with these efforts (Newman
et al. 1999, p. 2; Quinlan 2008, pers. comm.; Stott and Quinlan 2008,
p. 22). Reintroduction efforts in Michigan have recently been
terminated in the Gratiot, Little Carp, Hurricane, and Mosquito Rivers
and Sevenmile Creek (Scott 2007, pers. comm.; Loope 2007, pers. comm.).
Threats to brook trout across its native range are also acting on
brook trout within the upper Great Lakes. A primary impact is the
presence of introduced fishes (e.g., non-native salmonids). Introduced
salmonids have competitive and predatory impacts on brook trout,
although the precise mechanisms may not be fully understood and the
magnitude of impact may vary by species, population size, and
environmental conditions. The decline or loss of the migratory coaster
form has diminished connectivity among populations that once operated
as metapopulations. Populations that occur in such isolated patches can
be lost, increasing the possibility of extirpation. As a species, brook
trout are known to be highly susceptible to exploitation by anglers
(Newman and Dubois 1996, p. 3; Newman et al. 2003, p. 11; Huckins et
al. 2008, p. 1322). Overharvest was a primary cause of the decline of
Great Lakes brook trout populations by the early 1900s, especially the
coaster ecotype, and continues to threaten some populations within the
region (Newman and Dubois 1996, p. 1; Huckins et al. 2008, p. 1322;
Schreiner et al. 2008, p. 1356). Climate change also presents a threat
to upper Great Lakes brook trout, through increased water temperatures,
leading to increased presence of nonnative competitors and predators
along with a decrease in habitat suitability. Although the enormous
coldwater reservoir within the lake environment represents a potential
refuge for Great Lakes brook trout, predicted impacts in both stream
and lake environments still represent a potential threat to their long-
term viability.
Defining a Species Under the Act
Section 3(16) of the Act defines ``species'' to include ``any
species or subspecies of fish and wildlife or plants, and any distinct
vertebrate population segment of fish or wildlife that interbreeds when
mature'' (16 U.S.C. 1532 (16)). Our implementing regulations at 50 CFR
424.02 provide further guidance for determining whether a particular
taxon or population is a species or subspecies for the purposes of the
Act: ``The Secretary shall rely on standard taxonomic distinctions and
the biological expertise of the Department and the scientific community
concerning the relevant taxonomic group'' (50 CFR 424.11). As
previously discussed, coaster brook trout are classified as Salvelinus
fontinalis, the same as other brook trout, and as such we do not
consider the coaster form of the brook trout to constitute a distinct
species or subspecies. Since the coaster brook trout is not a distinct
species or subspecies, we then evaluated whether the coaster brook
trout is a distinct vertebrate population segment to determine whether
it would constitute a listable entity under the Act.
To interpret and implement the distinct vertebrate population
segment (DPS) provisions of the Act and Congressional guidance, the
Service and the National Marine Fisheries Service (now the National
Oceanic and Atmospheric Administration--Fisheries), published the
Policy Regarding the Recognition of Distinct Vertebrate Population
Segments (DPS Policy) in the Federal Register on February 7, 1996 (61
FR 4722). Under the DPS Policy, three elements are considered in the
decision regarding the establishment and classification of a population
of a vertebrate species as a possible DPS. These are applied similarly
for additions to and removals from the List of Endangered and
Threatened Wildlife and Plants. These elements are (1) the discreteness
of a population in relation to the remainder of the species to which it
belongs, (2) the significance of the population segment to the species
to which it belongs, and (3) the population segment's conservation
status in relation to the Act's standards for listing, delisting, or
reclassification.
Distinct Vertebrate Population Segment Analysis
In accordance with our DPS Policy, this section details our
analysis of the first two elements used to assess whether a vertebrate
population segment under consideration for listing may qualify as a
DPS. These elements are (1) the population segment's discreteness from
the remainder of the species to which it belongs and (2) the
significance of the population segment to the species to which it
belongs. Discreteness refers to the ability to circumscribe a
population segment from other members of the taxon based on either (1)
physical, physiological, ecological, or behavioral factors or (2)
international boundaries that result in
[[Page 23383]]
significant differences in control of exploitation, habitat management,
conservation status, or regulatory mechanisms in light of section
4(a)(1)(B) of the Act.
Under our DPS Policy, if we have determined that a vertebrate
population segment is discrete, we consider its biological and
ecological significance to the larger taxon to which it belongs in
light of Congressional guidance (see Senate Report 151, 96th Congress,
1st Session) that the authority to list DPSs be used ``sparingly''
while encouraging the conservation of genetic diversity. To evaluate
whether a discrete vertebrate population may be significant to the
taxon to which it belongs, we consider the best available scientific
evidence. This evaluation may include, but is not limited to: (1)
Evidence of the persistence of the discrete population segment in an
ecological setting that is unusual or unique for the taxon; (2)
evidence that loss of the population segment would result in a
significant gap in the range of the taxon; (3) evidence that the
population segment represents the only surviving natural occurrence of
a taxon that may be more abundant elsewhere as an introduced population
outside its historical range; and (4) evidence that the discrete
population segment differs markedly in its genetic characteristics from
other populations of the species.
The first step in our DPS analysis was to identify population
segments of the brook trout to evaluate. The petition asked us to (1)
``list as `endangered' the naturally spawning anadromous (lake-run)
Coaster Brook Trout (Salvelinus fontinalis) throughout its known
historic range in the conterminous United States'' (including
designation of critical habitat) and (2) ``determine whether the Salmon
Trout River (STR) coaster is a DPS'' and (3) ``whether the south shore
of Lake Superior population of coasters (which are known to breed today
only in the STR) is `endangered.' '' Although brook trout in the Great
Lakes exhibit three life-history forms (fluvial, adfluvial, and
lacustrine), the petition specifically focused on the coaster, or
adfluvial and lacustrine, forms.
To address the entity identified in the first petition request
(coaster brook trout throughout their historical range in the U.S.), we
identified two approaches to analyzing a potential population segment:
(1) Describe and analyze an upper Great Lakes ``all brook trout''
population segment, which includes all brook trout life forms--fluvial,
adfluvial, and lacustrine ecotypes, inclusive of coaster brook trout--
present throughout the documented historical range of brook trout in
the Great Lakes basin, and (2) describe and analyze an upper Great
Lakes ``coaster-only'' population segment, which includes only the
coaster forms--adfluvial and lacustrine ecotypes--of brook trout
throughout the documented historical range of brook trout in the Great
Lakes basin.
We find that neither of the population segments analyzed constitute
a valid DPS, and therefore the first petitioned entity, coaster brook
trout throughout their historical range in the U.S., is not a valid
DPS. To address the second and third petition requests, we focused on
the brook trout population in the Salmon Trout River and evaluated
whether it qualified as a DPS per our policy. We find that the brook
trout population in the Salmon Trout River also does not constitute a
valid DPS. The remainder of this section details the evaluation of
these population segments as DPSs per our 1996 DPS Policy.
Upper Great Lakes All Brook Trout Population Segment
This population segment encompasses the range of brook trout
populations within the Great Lakes basin that currently or historically
occupied both the tributary and lake environments (including stream-
resident, adfluvial, and lacustrine ecotypes of brook trout). Although
technically not one of the ``Great Lakes,'' we include Lake Nipigon in
Canada in this population because it is part of the Great Lakes
drainage. The best available information indicates the known historical
range of brook trout within the basin included all of Lake Superior and
its drainage (including Lake Nipigon), and the northern portions of
Lakes Michigan and Huron--specifically, that portion of Lake Michigan
north of a line from the Sheboygan River, Wisconsin to Grand Traverse
Bay, Michigan, and that portion of Lake Huron north of Thunder Bay,
Michigan, eastward to include Manitoulin Island to the 81[deg]30'
longitudinal demarcation and west of 81[deg]30' longitude (MacCrimmon
and Campbell 1969, p. 1701; Dehring and Krueger 1985, p. 1; Enterline
2000, pp. 29-30).
Discreteness
Marked Separation
As previously described, the Upper Great Lakes brook trout
population segment we have evaluated encompasses the range of brook
trout populations that currently or historically occupied both the
tributary and lake environments within the Great Lakes basin. Brook
trout within this population segment are physically isolated from other
populations of brook trout as the result of the physical separation
between the drainage of the Great Lakes basin and neighboring
drainages. Consequently, brook trout in the Great Lakes basin meet the
discreteness criterion of being markedly separate from other members of
the brook trout taxon.
International Border
We presently do not find that the brook trout in the Upper Great
lakes on either side of the international United States border with
Canada are discrete due to differences in control of exploitation,
management of habitat, conservation status, or regulatory mechanisms
that are significant in light of section 4(a)(1)(D) of the Act.
Conclusion for Discreteness
In conclusion, we determine that the Upper Great Lakes brook trout
population segment, as defined here, is discrete from the remainder of
the brook trout taxon. This discreteness arises from the population
segment's physical isolation from the remainder of the taxon.
Therefore, we will now consider the potential significance of this
discrete population segment to the remainder of the taxon.
Significance
We have determined that the population of brook trout in the Upper
Great Lakes meets the discreteness elements of the DPS policy, and as
such, we will now evaluate whether this specific population is
significant to the taxon as a whole (i.e., native brook trout in
eastern North America). A discrete population is considered significant
under the DPS policy if it meets one of four of the elements identified
in the policy under significance or can otherwise be reasonably
justified as being significant.
We discuss further below our evaluation of the significance of the
population of brook trout in the Upper Great Lakes relative to the
taxon as a whole.
Evidence of the Persistence of the Discrete Population Segment in an
Ecological Setting That Is Unusual or Unique for the Taxon
On the basis of an evaluation of the best available scientific
information, we have determined that the habitat for brook trout in the
Upper Great Lakes does not represent an ecological setting that is
unusual or unique for the native brook trout relative to the habitat
available to it throughout the entire
[[Page 23384]]
taxon's range in eastern North America. A summary of our evaluation is
below.
Brook trout exhibiting differing life-history forms occupy a
variety of ecosystems from subarctic regions of the Hudson Bay coast,
to temperate areas bordering and east of the Great Lakes, and southern
coldwater habitats in the Appalachian Mountains of Tennessee and
Georgia (Power 1980, p. 142). They have been successfully naturalized
in western North America, South America, Eurasia, Africa, and New
Zealand (MacCrimmon and Campbell 1969, p. 1699, pp. 1703-1717). Within
their large native range in eastern North America, brook trout habitat
includes coastal areas and various-sized lakes, streams, and rivers at
varying altitudes. Most populations inhabit coldwater streams, but
lake-dwelling and lake-spawning (lacustrine form) populations also
occur throughout the range, in spring-fed ponds, small- to medium-sized
lakes, and a few large, oligotrophic (containing relatively little
plant life or nutrients, but rich in dissolved oxygen) lakes.
Anadromous populations (``salters'') of brook trout use marine habitats
in Hudson Bay and along the Atlantic coast.
The upper Great Lakes represent a complex ecological setting for
brook trout. The very large size of the Great Lakes watershed creates
an environment that more closely resembles oceanic physical conditions
(available to the anadromous forms of brook trout) than conditions in
smaller lakes (available to other forms of brook trout). With
approximately 1,500 tributaries and almost 2,800 miles (4,506 km) of
shoreline, Lake Superior also provides brook trout access to a very
large freshwater habitat network. Although the Great Lakes are the
largest freshwater water bodies occupied by brook trout, there are
thousands of lakes in its range including large postglacial lakes
further north in Canada that contain populations of the adfluvial and
lacustrine forms (e.g., Fraser and Bernatchez 2008, p. 1193).
If predicted rising water temperatures in response to climate
change are realized over the entire range of brook trout, the
distributions of brook trout populations would probably shift toward
cooler waters at higher latitudes and altitudes (Meisner 1990b, p.
1068; Magnuson et al. 1997, p. 859; Kling et al. 2003, pp. 53-54). The
greatest effects would likely begin in populations located at the
margins of the taxon's hydrologic and geographic distributions (Meisner
et al. 1990a, p. 282, Kling et al. 2003, p. 54). Although the upper
Great Lakes have already experienced some impacts of climate change
(see Kling et al. 2003, pp. 14-16) and will not be immune to future
impacts (see Kling et al. 2003, pp. 21-25), they may provide
substantial coldwater habitat for brook trout in the future. However,
brook trout have abundant coldwater habitat available in the northern
latitudes of its range, and habitat in northern North America which is
presently too cold may develop into appropriate brook trout habitat
under a warming scenario. We will further evaluate the extent that this
may be the case in the range-wide assessment of native brook trout that
we plan to conduct (see Finding section).
Although the upper Great Lakes represent a diverse and complex
ecological setting which may offer potential coldwater habitat for
brook trout, we must evaluate the breadth of ecological diversity of
brook trout habitat rangewide in our assessment of this population
segment's significance to the rest of the taxon. First, available
information indicates that the large area and wide geographical range
of brook trout habitats, which vary in latitude and altitude and water
form, contain a vast diversity of habitats for brook trout. The
ecological setting of the upper Great Lakes is a small portion of the
brook trout range, and based on available information, its relative
significance to the brook trout species is limited. Second, although we
expect that the Great Lakes may offer substantial coldwater habitat,
there are other large, deep, oligotrophic lakes, and numerous lakes and
streams at higher latitudes that may buffer the species from potential
climate change impacts. Given the available information on the
diversity and extent of ecological settings of brook trout in the rest
of its range, we conclude at this time that the upper Great Lakes is a
not unique or unusual setting of significance for the native brook
trout in eastern North America.
Evidence That Loss of the Population Segment Would Result in a
Significant Gap in the Range of the Taxon
Loss of brook trout, including any or all life forms, in the upper
Great Lakes, when considered in relation to brook trout throughout the
remainder of the species' range in eastern North America, would mean
the loss of a small geographic portion (approximately ten percent) of
the entire range of the taxon. Further, the number of streams with
populations in the upper Great Lakes (about 200) are a small proportion
of the amount of streams and lakes with brook trout populations in the
rest of the native range in eastern North America. Due to the broad
geographic range of brook trout, the wide diversity of habitats
available to it, and its plasticity, and the fact that the upper Great
Lakes are at the western periphery of its natural range, we find that
the gap in the range resulting from the loss of brook trout in the
upper Great Lakes would not be significant.
Evidence That the Population Segment Represents the Only Surviving
Natural Occurrence of a Taxon That May Be More Abundant Elsewhere as an
Introduced Population Outside Its Historical Range
This criterion from the DPS policy does not apply to the brook
trout in the upper Great Lakes because it is not a population segment
representing the only surviving natural occurrence of the taxon that
may be more abundant elsewhere as an introduced population outside its
historical range. Consequently, this population of brook trout does not
meet the significance element of this factor.
Evidence That the Discrete Population Segment Differs Markedly in Its
Genetic Characteristics From Other Populations of the Species
A large amount of rangewide genetic variation for brook trout is
distributed among brook trout populations (large Fst values, values in
a fixation index which describe the degree of population
differentiation based on genetic polymorphisms). This pattern is
heavily influenced by the ecological and life-history characteristics
of brook trout populations (population connectivity or isolation,
philopatric tendency).
We find that, based on the genetic information currently available
(outlined under the Brook Trout Genetics section above), the brook
trout in the upper Great Lakes, including all life forms, do not differ
markedly from other populations of the species in their genetic
characteristics (such as exhibiting unique alleles or a proportion of
genetic variability beyond the norm of distribution) such that they
should be considered biologically or ecologically significant based
simply on genetic characteristics. They do not show any more genetic
distinctiveness in comparison to the remainder of the taxon than other
populations demonstrate. With the additional consideration that the
authority to list DPSs be used ``sparingly,'' we conclude that this
population segment of brook trout does not meet the significance
element of this factor.
DPS Conclusion--Upper Great Lakes All Brook Trout Population Segment
On the basis of the best available information, we conclude that
the all-
[[Page 23385]]
brook-trout population segment in the Upper Great Lakes is discrete due
to marked separation as a consequence of physical, ecological,
physiological, or behavioral factors according to the 1996 DPS Policy.
However, on the basis of an evaluation of brook trout in the Great
Lakes relative to the four significance elements of the 1996 DPS
Policy, we conclude that this discrete population segment is not
significant to the taxon to which it belongs, and therefore, does not
qualify as a DPS under 1996 policy. As such, we find that population of
brook trout in the Great Lakes basin is not a listable entity under the
Act.
Upper Great Lakes Coaster-Only Brook Trout Population Segment
This population segment encompasses the historical range of brook
trout populations in the Great Lakes basin exhibiting the coaster
ecotypes, which includes northern portions of the Lakes Michigan and
Huron and all of Lake Superior, including Lake Nipigon (see
Discreteness analysis for the Upper Great Lakes All Brook Trout
Population Segment below for more detailed range description).
Discreteness
Hubbs and Lagler (1949, p. 44) and Becker (1983, p. 320) described
coasters as brook trout that spend a portion of their life cycle in the
Great Lakes. Coaster brook trout have long been recognized by local and
scientific communities (Newman and Dubois 1997, p. 4).
Marked Separation
As described previously, coasters are adfluvial and lacustrine life
forms of brook trout that occupy the nearshore zone of the Great Lakes.
Coasters, being a subset of brook trout within the Great Lakes basin,
are markedly separate from all other brook trout outside of the Great
Lakes Basin as the result of the physical separation between the
drainage of the Great Lakes basin and neighboring drainages. Thus,
brook trout within this population segment are markedly separate from
other members of the brook trout taxon outside the Great Lakes basin
because they are physically isolated.
Isolation also exists within the Great Lakes basin, among brook
trout populations in Lakes Huron, Michigan, Erie, and Ontario. The best
available information indicates that adfluvial brook trout likely did
not historically occupy lake waters of southern Lakes Michigan and
Huron (boundary as previously defined in this section) or Lakes Erie
and Ontario (MacCrimmon and Campbell 1969, p. 1700; Bailey and Smith
1981, p. 1549; Dehring and Krueger 1985, p. 1; MIDNR 2008a, pp. 2-3).
Brook trout found within these lake areas in the last 100 years are
likely the result of stocking as no known adfluvial, migratory or lake
dwelling populations exist. The reason that brook trout never occupied
these lake areas is unknown; we suspect that unidentified environmental
conditions preclude brook trout use of these habitats. Regardless,
without brook trout use of the lake environment, natural dispersal
between stream populations cannot occur. This absence of adfluvial and
lacustrine ecotypes in these populations effectively restricts
populations with coaster brook trout forms to the distribution
previously defined, namely the watershed and lake habitats of all of
Lake Superior, and the northern portions of Lakes Michigan and Huron.
Within the Great Lakes basin, coasters are ecologically,
behaviorally, and physiologically discrete from stream-resident brook
trout. Coasters are markedly separate from resident brook trout in
their lake-dwelling and adfluvial behavior (Hubbs and Lagler 1949, p.
44; Becker 1983, p. 320; Huckins and Baker 2008, p. 1229; Schreiner et
al. 2008, p. 1350). Lake-dwelling coasters spend their entire life
within the lake environment (Huckins et al. 2008, p. 1323; Schreiner et
al. 2008, p. 1350); adfluvial coasters move between streams and the
lake (Huckins et al. 2008, p. 1323). Stream-resident brook trout remain
within the river system. These differences mark an ecological (i.e.,
lake versus stream habitat) and a behavioral (i.e., migratory)
separation between the two forms.
Coaster ecotypes and stream-resident ecotypes of brook trout also
differ physiologically in adult size, longevity, age at maturity, and
fecundity. As stated in the Species Description section above, adult
coasters range in size from 12 to 25 in (30 to 64 cm), and commonly
reach lengths of 16 in (41 cm) (Ritchie and Black 1988, pp. 50-51;
Quinlan 1999, p. 17; Huckins and Baker 2008, p. 1239; Huckins et al.
2008, p. 1337). The body mass of adult coasters typically ranges from
0.75 to 8 pounds (341 to 3632 g) (Quinlan 1999, p. 16; Swainson 2001,
p. 60; Huckins and Baker 2008, p. 1239; WIDNR and USFWS 2005, p. 16)
with a maximum measurement of 14.5 pounds (6577 g) (Scott and Crossman
1973, p. 211). Adult resident brook trout typically range in size from
5 to 15 in (13 to 38 cm) (Scott and Crossman 1979, p. 208; Becker 1983,
pp. 318, 320; WIDNR and USFWS 2005, p. 16; Schram 2008a pers. comm.)
and usually weigh less than a pound (<454 g) (WIDNR and USFWS 2005, p.
16). Most female coasters do not reach maturity until they are 2 to 4
years old and 12 to 15 in. (30 to 38 cm) in length (Ritchie and Black
1998, p. 19; Quinlan 1999, p. 11; Huckins and Baker 2008, p. 1241;
Huckins et al. 2008, p. 1329), and live 5 to 8 years (Quinlan 1999, p.
11; Huckins et al. 2008, p. 1328). Whereas most female stream-resident
brook trout mature by age 1 or 2 (Becker 1983, p. 318), and typically
live to age 3 and rarely reach ages of 4 or 5 years (Scott and Crossman
1973, p. 211, Becker 1983, p. 318). Coaster females produce around
1,500 to 3,000 eggs (Quinlan 1999, p. 20; Swainson 2001, p. 41), while
stream-resident brook trout fecundity ranges from 100 to 1,500 eggs per
female (Scott and Crossman 1973, p. 210; Power 1980, p. 157; Becker
1983, p. 318).
We recognize that many of the ecological, physiological, and
behavioral characteristics discussed here are influenced to varying
extents by environmental factors. For example, fish exhibit
indeterminate growth, where adults can reach larger sizes in larger
habitats with more favorable growth conditions or greater prey
availability, but may be more diminutive under less favorable habitat
conditions (Huckins et al. 2008, p. 1323). To this effect, many
physiological characteristics of coasters would be expected to differ
from their stream-resident counterparts, with coasters being larger
than residents, simply because coasters access the more productive lake
environments. In addition, many of the characteristics we evaluate are
interrelated, with one characteristic influencing or determining one or
more of the other characteristics. For example, fecundity is largely a
function of the size and condition of the fish. Also, prey selection
will be influenced by the prey availability in different habitat types.
We rely on all the characteristics taken together to describe the
phenotypic characteristics of each type. Regardless of the source of
the phenotypic characteristics of the types, be they controlled by
genetic heritability, environmental influences, or both, they
accumulate to form a description of each form and that defines either
their similarity or separation.
We further recognize that upper Great Lakes brook trout display a
continuum of traits in most of the characteristics described. However,
the range of overlap is small in comparison to the broader range of
difference between the two forms, with the majority of adult coasters
and stream-residents clearly
[[Page 23386]]
occupying nonoverlapping portions of the continuum. Further, at the end
of the continuum of traits, coasters are markedly separate in their use
of Great Lakes habitat. As we stated in adopting the DPS Policy in
1996, ``logic demands a distinct population recognized under the Act be
circumscribed in some way that distinguishes it from other
representatives of its species. The standard established for
discreteness is simply an attempt to allow an entity given DPS status
under the Act to be adequately defined and described'' (61 FR 4721, at
4724; February 7, 1996). In the case of brook trout in the Great Lakes,
there is a group that can be clearly distinguished by a variety of
characteristics, particularly its use of the Great Lakes habitat, which
leads to or results from marked separation in the other
characteristics.
Despite the apparent reproductive exchange and genetic similarity
between stream-resident forms and coaster forms of brook trout, the
life forms remain markedly separated physiologically, ecologically, and
behaviorally. The DPS Policy states that ``the standard adopted [for
discreteness] does not require absolute separation of a DPS from other
members of its species, because this can rarely be demonstrated in
nature for any population of organisms * * * [T]he standard adopted
allows for some limited interchange among population segments
considered to be discrete, so that loss of an interstitial population
could well have consequences for gene flow and demographic stability of
a species as a whole'' (61 FR 4722; February 7, 1996). Coasters are a
group of organisms that can be distinguished from stream-resident brook
trout by a variety of characteristics, particularly its migratory life
strategy and use of the Great Lakes.
Thus, given marked separation in physical, physiological,
ecological, and behavioral factors, we conclude that the coaster-only
population segment is discrete from Great Lakes stream-resident brook
trout. Further, as stated above, given its marked separation from all
other brook trout outside of the Great Lakes Basin as the result of the
physical separation between the drainage of the Great Lakes basin and
neighboring drainages, the coaster-only population segment is discrete
from brook trout outside the Great Lakes basin. Consequently, we find
that the coaster-only population satisfies the element of marked
separation under the 1996 DPS Policy, and is therefore considered to be
a discrete population per our policy.
International Border
We presently do not find that this population segment of the brook
trout on either side of the international United States border with
Canada is discrete due to differences in control of exploitation,
management of habitat, conservation status, or regulatory mechanisms
that are significant in light of section 4(a)(1)(D) of the Act.
Significance
We must next evaluate whether the coaster brook trout population
segment is significant to the larger brook trout taxon. We find that,
although we determined that coaster brook trout are a discrete
population segment, they co-occur with and are a subset of the same
population as other brook trout types (stream residents) in the upper
Great Lakes (see Species Information section above). Review of the best
available scientific information does not suggest that the coaster and
resident life forms in these populations are genetically distinct from
each other, indicating that they are part of one breeding population
(D'Amelio and Wilson 2008, p. 1221; Scribner et al. 2008, p. 10). Thus,
similar to our Upper Great Lakes All Brook Trout population segment,
the loss of coasters would not create a significant gap in the range of
the taxon, they are not the only remaining natural occurrence of the
taxon, and they do not show significant genetic distinctiveness in
comparison to the remainder of the taxon. In addition, coasters occupy
a smaller portion of the same ecological setting as other brook trout
in the upper Great Lakes. Although, as discussed above, coasters may be
important to the long-term viability of brook trout populations
throughout Lake Superior, the relevant question is whether coasters are
significant to the taxon as a whole, here, all native brook trout.
Given this, the significance analysis documented for the all brook
trout population segment (see Upper Great Lakes All Brook Trout DPS
section above) also applies to the coaster-only population segment, and
we similarly conclude that the coaster-only population segment does not
meet the significance elements of the DPS Policy.
DPS Conclusion--Coaster-Only Population Segment
On the basis of the best available information, we conclude that
the coaster-only population segment in the Upper Great Lakes is
discrete due to marked separation as a consequence of physical,
ecological, physiological, or behavioral factors according to the 1996
DPS policy. However, on the basis of the four significance elements in
the 1996 DPS Policy, we conclude that this discrete population segment
is not significant to the rest of the taxon, and therefore, does not
qualify as a valid DPS under our 1996 DPS Policy. As such, we find that
the coaster-only population in the upper Great Lakes is not a listable
entity under the Act.
Salmon Trout River/South Shore Lake Superior Brook Trout Population
Segment
This section evaluates whether the Salmon Trout River-South Shore
Lake Superior brook trout population segment qualifies as a DPS. Since
the Salmon Trout River contains the only known brook trout population
with naturally reproducing coaster on the South Shore of Lake Superior,
we addressed these two petition requests in one analysis.
Discreteness
Markedly Separate
The brook trout population segment that occupies the Salmon Trout
River is markedly separate from other members of the brook trout taxon
because it is genetically or reproductively isolated. This physical
isolation is supported by recent evidence from Scribner et al. (2008,
pp. 12-13), which found no genetic evidence of Salmon Trout River fish
in neighboring streams, indicating that Salmon Trout River coasters are
not a source of gene flow among streams.
International Border
Since the Salmon Trout River population segment does not cross an
international border, this basis for finding discreteness is not
applicable.
In conclusion, the Salmon Trout River brook trout population
segment, as defined here, meets the element for discreteness under our
1996 DPS Policy and is considered discrete from the remainder of the
brook trout taxon. This discreteness arises from the population
segment's genetic or reproductive isolation from the remainder of the
taxon which is supported by evidence of genetic discontinuity.
Significance
Evidence of the Persistence of the Discrete Population Segment in an
Ecological Setting That Is Unique for the Taxon
The ecological setting for the Salmon Trout River discrete
population segment is similar to that of other brook trout populations
throughout the upper Great Lakes region. We are unaware of any features
that make the Salmon Trout River unique or unusual in terms of
[[Page 23387]]
brook trout habitat. There is nothing about the ecological setting that
is unique or unusual for the species, particularly in light of the
other occurrences within Lake Superior. Consequently, this population
of brook trout does not meet the significance element of this factor.
Evidence That Loss of the Population Segment Would Result in a
Significant Gap in the Range of the Taxon
This criterion from the DPS policy does not apply to the Salmon
Trout River discrete population segment because this population is one
of thousands of brook trout populations existing throughout the range
of the taxon and its loss would represent an extremely small portion of
the range. Consequently, this population of brook trout does not meet
the significance element of this factor.
Evidence That the Population Segment Represents the Only Surviving
Natural Occurrence of a Taxon That May Be More Abundant Elsewhere as an
Introduced Population Outside Its Historical Range
This criterion from the DPS policy does not apply to the Salmon
Trout River discrete population segment because it is not a population
segment representing the only surviving natural occurrence of the taxon
that may be more abundant elsewhere as an introduced population outside
its historical range. Consequently, this population of brook trout does
not meet the significance element of this factor.
Evidence That the Discrete Population Segment Differs Markedly in Its
Genetic Characteristics From Other Populations of the Species
Scribner et al. (2008, p. 9) indicates that Lake Superior brook
trout populations, including the Salmon Trout River, are highly
genetically structured with low levels of gene flow among populations.
The Salmon Trout River contains two genetically distinct populations
that are separated by impassable waterfalls (Scribner et al. 2008, p.
10). Both populations in the Salmon Trout River were equally
genetically diverged from the other populations included in the study
(Scribner et al. 2008, p. 7). This pattern of population genetic
structuring is common in brook trout throughout the species' range
because, like many salmonids, this species likely exhibits some degree
of spawning site fidelity (Angers et al. 1999, p. 1044; D'Amelio et al.
2008, pp. 1347-1348; Mucha and Mackereth 2008, p. 1211). This degree of
genetic divergence that forms among populations is reflective of the
reproductive connections (isolation) among the populations across the
range of the taxon.
We are unaware of any information indicating that this population
segment differs from the species in its genetic characteristics (such
as exhibiting unique alleles or a proportion of genetic variability
beyond the norm of distribution) such that it should be considered
biologically or ecologically significant to the taxon based on genetic
characteristics. Consequently, this population of brook trout does not
meet the significance element of this factor.
DPS Conclusion--Salmon Trout River/South Shore Lake Superior Population
Segment
On the basis of the best available information, we conclude that
the Salmon Trout River brook trout population segment is ``markedly
separated'' from all other populations of the same taxon as a
consequence of physical factors, supported by genetic evidence.
Consequently, the Service concludes that the petitioned entity is
discrete according to the 1996 DPS Policy. However, on the basis of an
evaluation of the four significance elements of the 1996 DPS Policy, we
conclude that this discrete population segment is not significant to
the species to which it belongs. Therefore, we find that the Salmon
Trout River brook trout population does not qualify as a DPS under our
DPS Policy and is consequently not a listable entity under the Act.
Significant Portion of the Range Analysis
The Act defines an endangered species as one ``in danger of
extinction throughout all or a significant portion of its range,'' and
a threatened species as one ``likely to become an endangered species
within the foreseeable future throughout all or a significant portion
of its range.'' Having determined that the northern Great Lakes
population segment of brook trout and the Salmon Trout River/South
Shore Lake Superior populations of the coaster brook trout do not meet
the elements of our 1996 DPS Policy as being valid DPSs, we then
assessed whether the upper Great Lakes brook trout is a significant
portion of the range (SPR) of the native brook trout where the species
is in danger of extinction or likely to become so in the foreseeable
future.
On March 16, 2007, a formal opinion was issued by the Solicitor of
the Department of the Interior, ``The Meaning of `In Danger of
Extinction Throughout All or a Significant Portion of Its Range' ''
(DOI 2007). We have summarized our interpretation of that opinion and
the underlying statutory language below. A portion of a species' range
is significant if it is part of the current range of the species and is
important to the conservation of the species because it contributes
meaningfully to the representation, resiliency, or redundancy of the
species. The contribution must be at a level such that its loss would
result in a decrease in the ability of the species to persist.
The first step in determining whether a species is endangered in an
SPR is to identify any portions of the range of the species that
warrant further consideration. The range of a species can theoretically
be divided into portions in an infinite number of ways. However, there
is no purpose to analyzing portions of the range that are not
reasonably likely to be significant and threatened or endangered. To
identify those portions that warrant further consideration, we
determine whether there is substantial information indicating that (i)
the portions may be significant and (ii) the species may be in danger
of extinction there. In practice, a key part of this analysis is
whether the threats are geographically concentrated in some way. If the
threats to the species are essentially uniform throughout its range, no
portion is likely to warrant further consideration. Moreover, if any
concentration of threats applies only to portions of the range that are
unimportant to the conservation of the species, such portions will not
warrant further consideration.
The petition specified two portions of the range of brook trout:
(1) The historical range of coaster brook trout in the contiguous U.S.,
namely the upper Great Lakes, and (2) the Salmon Trout River/South
Shore Lake Superior. In our SPR analysis, we assessed threats to brook
trout in these portions in comparison to threats acting on other
portions of the range. Information on threats within the upper Great
Lakes region included primarily habitat degradation, overutilization,
nonnative fishes, and loss of connectivity and life-history diversity.
We had comparatively less detailed information on the threats acting
throughout the rest of the range. The best information available to us
regarding other portions of the brook trout range was found in analyses
completed for the Eastern Brook Trout Joint Venture (see Hudy et al.
2005, TU 2006). Given the information available to us on threats to
brook trout across its range, we conclude that threats to this species
were similar throughout its range, that the conservation status of the
species is similar throughout its range,
[[Page 23388]]
and that there is no area within the range of the upper Great Lakes and
the Salmon Trout River/South Shore Lake Superior portions of the
coaster brook trout where potential threats to this species are
significantly concentrated or are substantially greater than in other
portions of the range. We found no evidence that more threats were
geographically concentrated within the upper Great Lakes than in any
other part of the range; according to the findings of Hudy et al.
(2005), it seems that threats may be greater in portions of the
Northeastern U.S. populations than in the Great Lakes.
Therefore, we find that the brook trout is not threatened or
endangered solely in any significant portion of its range within the
upper Great Lakes. As stated in the Finding section below, we plan to
initiate a range-wide assessment of the native brook trout that will
enable us to better understand the status of the native brook trout
across the range of species, including a determination of whether the
threats to the species, which are not concentrated in the upper Great
Lakes, warrant listing the native brook trout rangewide.
Finding
In making this finding, we considered information provided by the
petitioners, as well as other information available to us concerning
coaster brook trout. We have carefully assessed the best scientific and
commercial information available regarding the status of and threats to
coaster brook trout in the upper Great Lakes. We reviewed the petition,
and available published and unpublished scientific and commercial
information. We also consulted with Federal and State land managers,
along with recognized experts in conservation and population genetics
and brook trout and salmonid biology. This 12-month finding reflects
and incorporates information that we received from the public following
our 90-day finding or that we obtained through consultation, literature
research, and field visits.
On the basis of this review, we have determined that the coaster
brook trout in the upper Great Lakes does not meet the elements of our
1996 DPS Policy as being a valid DPS. We also find that the coaster
brook trout is not an SPR of the native brook trout and does not
warrant further consideration as such under the Act. Therefore, we find
that the coaster brook trout is not a listable entity under the Act,
and that listing is not warranted.
Although we find that population segments analyzed above are not
listable entities, we found enough information concerning the
diversity, habitats, population structure, threats, and trends of the
native brook trout in its entire range to initiate a range-wide
assessment that will enable us to better understand the status of the
native brook trout across the range of species. Completing a range-wide
assessment will allow us to better evaluate if any population would
meet the elements of the DPS policy or constitute an SPR of the taxon.
We will also continue to assess the status of and threats to both the
upper Great Lakes and Salmon Trout River/South Shore Lake Superior
populations of the coaster brook trout.
We request that you submit any new information concerning the
taxonomy, biology, ecology, and status of the brook trout in its entire
native range. Send this information to the Region 3 Fish and Wildlife
Service Regional Office (see ADDRESSES section) whenever it becomes
available. We will accept additional information and comments from all
concerned governmental agencies, the scientific community, industry, or
any other interested party concerning this finding; and will reconsider
this determination with new information as appropriate. The Service
continues to strongly support the cooperative conservation and
restoration of the coaster brook trout in the upper Great Lakes.
References
A comprehensive list of the referenced materials is available upon
request (see ADDRESSES section above).
Author
The primary authors of this document are staff located at the
Region 3 Fish and Wildlife Service Regional Office (see ADDRESSES).
Authority
The authority for this action is the Endangered Species Act of
1973, as amended (16 U.S.C. 1531 et seq.).
Stephen Guertin,
Acting Deputy Director, U.S. Fish and Wildlife Service.
[FR Doc. E9-11527 Filed 5-18-09; 8:45 am]
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