[Federal Register: May 14, 2008 (Volume 73, Number 94)]
[Proposed Rules]
[Page 27899-27926]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr14my08-29]
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Part II
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Status Review for Rio
Grande Cutthroat Trout; Proposed Rule
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS-R2-ES-2008-0056; 1111 FY07 MO-B2]
Endangered and Threatened Wildlife and Plants; Status Review for
Rio Grande Cutthroat Trout
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of candidate status review.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce the
results of the status review for the Rio Grande cutthroat trout
(Oncorhynchus clarki virginalis) under the Endangered Species Act of
1973 (Act), as amended. After a thorough review of all available
scientific and commercial information, we find that listing the Rio
Grande cutthroat trout is warranted but precluded by higher priority
actions. Upon publication of this status review, we will add the Rio
Grande cutthroat trout to our list of candidate species with a listing
priority number of 9, because the threats affecting it have a moderate
magnitude and are imminent. We will develop a proposed rule to list the
subspecies as our priorities allow. We ask the public to continue to
submit to us any new information that becomes available concerning the
status of or threats to the subspecies. This information will help us
to monitor and encourage the ongoing conservation of this subspecies.
DATES: The finding announced in this document was made on May 14, 2008.
ADDRESSES: This finding is available on the Internet at http://
www.regulations.gov. Supporting documentation we used in preparing this
finding is available for public inspection, by appointment, during
normal business hours at the U.S. Fish and Wildlife Service, New Mexico
Ecological Services Field Office, 2105 Osuna Road, NE., Albuquerque,
New Mexico 87113; telephone (505) 346-2525; facsimile (505) 248-6788.
Please submit any new information, materials, comments, or questions
concerning this finding to the above address or via electronic mail (e-
mail) at r2fwe_al@fws.gov.
FOR FURTHER INFORMATION CONTACT: Wally ``J'' Murphy, Field Supervisor,
U.S. Fish and Wildlife Service, 2105 Osuna Road, NE., Albuquerque, New
Mexico 87113. (505) 346-2525 ext 106. If you use a telecommunications
device for the deaf (TDD), 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 containing substantial scientific and commercial
information that listing may be warranted, we make a finding within 12
months of the date of receipt of the petition on whether the petitioned
action is: (a) Not warranted, (b) warranted, or (c) warranted, but that
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 Lists of Endangered and
Threatened Wildlife and Plants. 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 a subsequent finding to be made within 12
months. We must publish these 12-month findings in the Federal
Register.
Previous Federal Actions
On February 25, 1998, we received a petition from Kieran Suckling,
of the Southwest Center for Biological Diversity requesting that the
Service add the Rio Grande cutthroat trout (Oncorhynchus clarki
virginalis) to the list of threatened and endangered species. The
petition addressed the range-wide distribution of the Rio Grande
cutthroat trout that includes populations in Colorado and New Mexico.
We subsequently published a notice of a 90-day finding in the Federal
Register (63 FR 49062) on September 14, 1998. In the 90-day finding we
concluded that the petition did not present substantial information
indicating that listing of the Rio Grande cutthroat trout may be
warranted.
On June 9, 1999, a complaint was filed by the Southwest Center for
Biological Diversity alleging that the September 14, 1998, 90-day
petition finding violated the Administrative Procedure Act. While the
litigation was pending, we received information (particularly related
to the presence of whirling disease in hatchery fish in the wild) that
led us to believe that further review of the status of the subspecies
was warranted. On November 8, 2001, a settlement agreement executed by
both parties (the Service and the Southwest Center for Biological
Diversity) was filed with the court. The settlement stipulated that the
Service would initiate a status review for the Rio Grande cutthroat
trout, make a determination on or before June 4, 2002, and shortly
thereafter, publish our determination in the Federal Register. On June
11, 2002, we published our determination that listing of Rio Grande
cutthroat trout was not warranted (67 FR 39936).
Subsequently, on February 25, 2003, the Center for Biological
Diversity, along with several other organizations, sued the Service for
failing to list Rio Grande cutthroat trout. On June 7, 2005, the New
Mexico Federal District Court (Court) ruled that our finding was not
arbitrary and capricious, but also required that we explain in more
detail our analysis of ``significant portion of the range''. The Court
ordered the Service to provide a supplemental briefing discussing in
more detail our analysis of significant portion of the range. We
submitted this briefing on July 20, 2005. On December 19, 2005, the
Court ruled in favor of the Service and upheld our interpretation of
significant portion of the range and determined that our evaluation of
Rio Grande cutthroat trout's status under the listing criteria was not
arbitrary and capricious. Plaintiffs appealed this decision.
The appeal was pending with the Tenth Circuit Court of Appeals,
when other courts issued opinions for other species that required the
Service to reexamine our position on significant portion of the range.
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'' (U.S. DOI 2007).
Because of this new formal opinion and because of our knowledge of
changes in status of some populations that we had defined as ``secure''
in our 2002 review, in consultation with the court and the plaintiffs,
the Service agreed to initiate a new status review. We subsequently
published a notice seeking new information concerning the status of Rio
Grande cutthroat trout on May 22, 2007 (72 FR 28664).
In response to our 2007 requests for information regarding Rio
Grande cutthroat trout (72 FR 28664, 72 FR 46030 (August 16, 2007)), we
received comments and information from Colorado Division of Wildlife
(CDOW), New Mexico Department of Game and Fish (NMDGF), U.S. Bureau of
Land Management (BLM), U.S. Forest Service (USFS), private citizens and
organizations, and the Rio Grande Cutthroat Trout Conservation Team.
The Rio Grande Cutthroat Trout
[[Page 27901]]
Conservation Team is composed of biologists from CDOW, NMDGF, BLM,
USFS, National Park Service, the Jicarilla Apache Nation and the
Service. The Rio Grande Cutthroat Trout Conservation Team recently
completed a range-wide status report (Alves et al. 2007) concerning the
Rio Grande cutthroat trout. The status report and the comprehensive
database (referred to as ``2007 database'' in this finding) that is the
basis for the report, along with other supplemental submissions from
the agencies listed above, provide the best scientific and commercial
information available on Rio Grande cutthroat trout. The report
summarizes information provided by 15 fisheries professionals from
Colorado and New Mexico having specific knowledge of Rio Grande
cutthroat trout (Alves et al. 2007, p. 58). In making this finding, we
considered all scientific and commercial information that we received
or acquired since our previous status review. We relied primarily on
published and peer-reviewed documentation for our conclusions.
Biology and Distribution
The Rio Grande cutthroat trout, one of 14 subspecies of cutthroat
trout, is native to the Rio Grande, Pecos, and the Canadian river
basins in New Mexico and Colorado (Behnke 2002, p. 219). Rio Grande
cutthroat trout has the distinction of being the first North American
trout recorded by Europeans (Behnke 2002, p. 139). In 1541, Francisco
de Coronado's expedition discovered Rio Grande cutthroat trout in the
upper Pecos River (Behnke 2002, p. 139). The first specimens that were
collected for scientific purposes came from Ute Creek in Costilla
County, Colorado, in 1853. Rio Grande cutthroat trout was originally
described in 1856 (Behnke 2002, p. 210). Cutthroat trout subspecies are
distinguished by the red to orange slashes in the throat folds beneath
the lower jaw.
The historical distribution of Rio Grande cutthroat trout is not
known with certainty. In general, it is assumed that Rio Grande
cutthroat trout occupied all streams capable of supporting trout in the
Rio Grande, Pecos, and Canadian basins (Alves et al. 2007, p. 9). The
Pecos River is a tributary of the Rio Grande, so a historic connection
between the two basins likely existed. Although no early museum
specimens document its occurrence in the headwaters of the Canadian
River, it is almost certainly native there as well (Behnke 2002, p.
208). The Canadian River, tributary to the Mississippi River, has no
connection with the Rio Grande. It is possible that through headwater
capture (a tributary from one watershed joins with a tributary from
another) there may have been natural migration of fish between the
Pecos and Canadian headwater streams. There is evidence that Rio Grande
cutthroat trout may have occurred in Texas (Garrett and Matlock 1991,
p. 405; Behnke 1967, pp. 5, 6) and Mexico (Behnke 1967, p. 4).
Currently, the southernmost distribution of Rio Grande cutthroat trout
occurs in Animas Creek, Sierra County, New Mexico, and Indian Creek on
the Mescalero Apache Indian Reservation in Otero County, New Mexico.
Distribution in the southern portion of the range is currently limited
and no conservation populations (see discussion of conservation
populations below) exist south of Santa Fe, New Mexico.
In the range-wide status report, historically occupied habitat was
based on habitat believed to be inhabited by Rio Grande cutthroat trout
when early European explorers entered the Southern Rocky Mountain
Region of Colorado and New Mexico (circa 1800) (Alves et al. 2007, p.
9). In general, streams currently capable of supporting trout
(elevations of 1,829 meters (m) (6,000 feet (ft)) and above; 1,671 m
(5,500 ft) and above on north-facing slopes) were assumed to have been
historically occupied if they were not above a barrier to fish movement
(e.g., an impassable waterfall). Streams which cannot currently support
trout were assumed not to have been historically occupied unless they
were known to have been degraded by such things as water withdrawals,
channel alterations, human-caused barriers, or chemical contamination.
Based on these criteria, 10,622 kilometers (km) (6,660 miles (mi)) of
stream habitat were identified as having the potential of being
historically occupied by Rio Grande cutthroat trout (Alves et al. 2007,
p. 9). The estimated amount of historical range in each State is about
5,196 km (3,229 mi) in Colorado (48 percent), and 5,521 km (3,431 mi)
(52 percent) in New Mexico (Alves et al. 2007, p. 9).
To facilitate management and conservation efforts, the Rio Grande
cutthroat trout range is divided into Geographic Management Units
(GMUs) based on watersheds (Alves et al. 2007, p. 2). The GMUs are,
from north to south, Rio Grande headwaters, Lower Rio Grande, Canadian,
Pecos, and Caballo. Historical occupancy by GMU is 5,277 km (3,279 mi)
(49 percent) in Rio Grande Headwaters, 3,396 km (2,110 mi) (32 percent)
in Lower Rio Grande, 1,027 km (638 mi) (10 percent) in the Canadian,
1,003 km (623 mi) (9 percent) in Pecos, and 16 km (10 mi) (0.2 percent)
in Caballo (Alves et al. 2007, p. 9).
In our prior status review (67 FR 39936; June 11, 2002), we focused
our analysis primarily on ``core'' populations, which we defined using
conservative criteria for genetic integrity, population stability, and
security from invasion by nonnative salmonids (trout and salmon). The
genetic criterion for these core populations was that the populations
have less than one percent representation of genetic markers from
another subspecies of cutthroat trout or from rainbow trout
(Oncorhynchus mykiss), as determined by genetic testing. Rio Grande
cutthroat trout are able to interbreed, or hybridize, with other
subspecies of cutthroat trout and rainbow trout. This hybridization may
result in genes of one species or subspecies being incorporated into
the other species or subspecies. The incorporation of genes from one
species into another is referred to by the technical term
``introgression'' (Mayr 1970) and a species that has received such
genes is referred to as ``introgressed.'' To simplify discussion in
this review, we will also use these terms when describing when genetic
markers of another subspecies are found in Rio Grande cutthroat trout,
although we recognize that these terms, as strictly defined, refer to
species.
Our previous status review concluded that the core populations, as
then defined by conservative criteria, were sufficiently abundant,
distributed, and secure to conclude that listing of the Rio Grande
cutthroat trout was not warranted. As described later in this review,
the status of several of the original core populations has subsequently
declined and we believe those populations alone are not sufficient to
conserve the Rio Grande cutthroat trout.
For the current review, the genetic criterion for core populations
is that they be less than one percent introgressed, which is the same
genetic criterion for core populations followed in the previous review.
Although population stability and security from invasion are not used
to define core populations, as they were in the previous review, those
factors are still addressed as attributes affecting the status of core
and other populations. Core populations in the current review
correspond to the core populations described in the multi-state
position paper for cutthroat management (Utah Division of Wildlife
Resources (UDWR) 2000, pp. 3, 4). In addition to these core
populations, we focused our review on ``conservation populations'' as
defined
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by the position paper (UDWR 2000): populations less than 10 percent
introgressed, as measured by genetic markers, and that retain the
ecological, behavioral, and phenotypic characteristics of Rio Grande
cutthroat trout. In addition, we have included as conservation
populations those populations which have not been genetically tested,
but that retain the ecological, behavioral, and phenotypic
characteristics of Rio Grande cutthroat trout and are not suspected to
be introgressed or co-occurring with hybridizing species.
The above criteria for core and conservation populations have been
applied in Service status reviews of other subspecies of cutthroat
trout published since 2002 (71 FR 8818; 72 FR 32589). The status review
(68 FR 46989; August 7, 2003) for the westslope cutthroat trout
(Oncorhynchus clarki lewisi) included populations with up to 20 percent
introgression, based on several studies of genetic markers and
morphological traits of introgressed populations that indicate that
populations with up to 20 percent of their nuclear genes derived from
rainbow trout were morphologically indistinguishable from
nonintrogressed westslope cutthroat trout populations. Comparable
studies, where genetic and morphological characters in the same
population are studied, have not been performed on Rio Grande cutthroat
trout; therefore, we have no justification for departing from the
general criterion of less than 10 percent introgression proposed in the
position paper on cutthroat trout genetics (UDWR 2000).
In the remainder of this review, we collectively refer to both core
and conservation populations, as defined above, as conservation
populations.
Inclusion of conservation populations with up to 10 percent
introgression in the present review does not mean we are any less
concerned about the effects of introgression on Rio Grande cutthroat
trout. Our evaluation of introgression as a threat to the Rio Grande
cutthroat trout will be described along with other applicable threats
later in this review.
Alves et al. (2007, p. 26) report that 120 conservation populations
of Rio Grande cutthroat trout currently occupy about 1110 km (690 mi)
of habitat, or 10.4 percent of the historical range of the subspecies.
The 120 conservation populations include 12 populations that have not
been tested for introgression and are suspected to be hybridized and
one population that to date has tested as nonintrogressed but in which
rainbow trout, a hybridizing species, co-occurs (Alves et al. 2007, p.
34; 2007 data base). An additional two streams (Placer Creek and
Comanche Creek) included in the 120 are undergoing restoration and are
currently unoccupied by Rio Grande cutthroat trout. Although we fully
expect these two streams will become conservation populations within
the next five years, they are not occupied by viable populations
currently. Although we included in our analysis untested populations
that are suspected to be nonintrogressed as conservation populations,
we do not feel it is appropriate to include untested populations that
are suspected to be introgressed or that co-occur with hybridizing
species. Alves et al. (2007) provided all summary statistics (e.g.,
percent populations with nonnative trout, percent historical habitat
occupied, number of populations in each state) for 120 conservation
populations. Although the inclusion of these populations in Alves et
al. (2007) inflates the number of conservation populations and miles of
stream occupied by Rio Grande cutthroat trout, their inclusion does not
make a material difference in the outcome of our finding. Therefore, we
have decided to present all summary statistics as presented in Alves et
al. (2007) rather than recalculate the summary statistics to reflect
the 105 populations we would classify as conservation populations.
Rio Grande cutthroat trout conservation populations currently
occupy about 473 km (294 mi) in Colorado (9.1 percent of Colorado
historical habitat) and 637 km (396 mi) in New Mexico (11.6 percent of
historical habitat) (Alves et al. 2007, p. 26). The Lower Rio Grande
GMU contains the largest amount of occupied habitat (489 km (304.1
mi)), followed by the Rio Grande Headwaters GMU (452 km (281.4 mi)),
Canadian GMU (109 km (67.5 mi)), and Pecos GMU (60 km (37.3 mi)) (Alves
et al. 2007, p. 26). The Caballo GMU contains a hybridized population
of cutthroat trout that was not included as a conservation population.
Rio Grande cutthroat trout occupy habitat in 14 of 19 watersheds that
supported historical habitat. They are believed to be extirpated from
the following watersheds: Arroyo Del Macho, Caballo, Upper Canadian,
Rio Hondo, and Rio Penasco (Alves et al. 2007, p. 11). If Rio Grande
cutthroat trout once occurred in Texas and Mexico, there is no evidence
that they occur there now.
Life History
As is true of other subspecies of cutthroat trout, Rio Grande
cutthroat trout is found in clear cold streams. Unlike some subspecies
of cutthroat trout, such as the Bonneville (Oncorhynchus clarki utah)
and Yellowstone (Oncorhynchus clarki bouvieri), Rio Grande cutthroat
trout did not originally inhabit large lake systems. However, they have
been introduced into coldwater lakes and reservoirs. They spawn as high
water flows from snowmelt recede. In New Mexico, this typically occurs
from the middle of May to the middle of June (NMDGF 2002, p. 17).
Spawning is believed to be tied to day length, water temperature, and
runoff (Sublette et al. 1990, p. 54; Behnke 2002, p. 141).
It is unknown if Rio Grande cutthroat trout spawn every year or if
some portion of the population spawns every other year as has been
recorded for westslope cutthroat trout (McIntyre and Rieman 1995, p.
1). Likewise, while it is assumed that females mature at age 3, they
may not spawn until age 4 or 5 as seen in westslope cutthroat trout
(McIntyre and Rieman 1995, p. 3). Sex ratio also is unknown with
certainty, but based on field data, a ratio skewed towards more females
might be expected (Pritchard and Cowley 2006, p. 27). Although
Yellowstone (Gresswell 1995, p. 36), Bonneville (Shrank and Rahel 2004,
p. 1532), and westslope (Bjornn and Mallet 1964, p. 73; McIntyre and
Rieman 1995, p. 3) cutthroat trout subspecies are known to have a
migratory life history phase, it is not known if Rio Grande cutthroat
trout once had a migratory form when there was connectivity among
watersheds.
Most cutthroat trout are opportunistic feeders, eating both aquatic
invertebrates and terrestrial insects that fall into the water
(Sublette et al. 1990, p. 54). Rio Grande cutthroat trout evolved with
Rio Grande chub (Gila pandora), longnose dace (Rhinichthys cataractae)
(all basins); Rio Grande sucker (Catastomus plebius) (Rio Grande
Basin); white sucker (C. commersoni) and creek chub (Semotilus
atromaculatus) (Pecos and Canadian Basins); and the southern redbelly
dace (Phoxinus erythrogaster) (Canadian River Basin) (Rinne 1995, p.
24). Many of these fish have either been extirpated from streams with
Rio Grande cutthroat trout or are greatly reduced in number (Sublette
et al. 1990, p. 162; Calamusso and Rinne 1999, pp. 233-236). It is not
known if they once were an important component of Rio Grande cutthroat
trout diet. Other subspecies of cutthroat trout become more piscivorous
(fish eating) as they mature (Moyle 1976, p. 139; Sublette et al. 1990,
p. 54) and cutthroat trout living in lakes will prey heavily on other
species of fish (Echo 1954, p. 244). It is possible that native
cyprinids (i.e., chubs, minnows, and dace) and suckers may have once
been
[[Page 27903]]
important prey items for Rio Grande cutthroat trout. Growth of
cutthroat trout varies with water temperature and availability of food.
Most populations of Rio Grande cutthroat trout are found in high
elevation streams. Under these conditions growth may be relatively slow
and time to maturity may take longer than is seen in subspecies that
inhabit lower elevation (warmer) streams.
Typical of trout, Rio Grande cutthroat trout require several types
of habitat for survival: spawning habitat, nursery or rearing habitat,
adult habitat, and refugial habitat. Spawning habitat consists of clean
gravel (little or no fine sediment present) that ranges between 6 to 40
millimeters (mm) (0.24-1.6 inches (in)) (NMDGF 2002, p. 17). Nursery
habitat is usually at the stream margins where water velocity is low
and water temperature is slightly warmer. Harig and Fausch (2002, pp.
542, 543) found that water temperature may play a critical role in the
life history of the young-of-year cutthroat. Streams with mean daily
temperature in July of less than 7.8 [deg]C (46 [deg]F) may not have
successful recruitment (survival of individuals to sexual maturity and
joining the reproductive population) or reproduction in most years.
Adult habitat consists of pools with cover and riffles for food
production and foraging. Refugial habitat in the form of large deep
pools is also necessary for survival. The primary form of refugial
habitat is deep pools that do not freeze in the winter and do not dry
in the summer or during periods of drought. Lack of large pools may be
a limiting factor in headwater streams (Harig and Fausch 2002, p. 543).
Refugial habitat may also be a downstream reach of stream or a
connected adjacent stream that has maintained suitable habitat in spite
of adverse conditions.
A technical review of Rio Grande cutthroat trout was recently
completed (Pritchard and Cowley 2006) which covers the biology of the
subspecies in greater detail and the reader is referred to that
document for additional background information on the subspecies.
Summary of Factors Affecting the Subspecies
Section 4 of the Act and regulations (50 CFR 424) promulgated to
implement the listing provisions of the Act set forth the procedures
for adding species to the Federal list of endangered or threatened
species. A species may be determined to be threatened or endangered due
to one or more of the five factors described in section 4(a)(1) of the
Act. The following analysis examines the listing factors and their
application to Rio Grande cutthroat trout.
A. The Present or Threatened Destruction, Modification, or Curtailment
of Its Habitat or Range
Population Isolation and Fragmentation
The historic range of Rio Grande cutthroat trout has been greatly
reduced over the last 150 years. Populations have been lost because of
water diversions, stream drying, dams, habitat degradation, changes in
hydrology, hybridization with rainbow trout, or competition with brown
(Salmo trutta) and brook trout (Salvelinus fontinalis) (Pritchard and
Cowley 2006, pp. 16, 34-37; 67 FR 39939). Quantifying the exact
magnitude of loss in either number of fish or habitat is difficult
because there are no baseline data. Alves et al. (2007, p. 26) estimate
that conservation populations occupy about 10 percent of historically
inhabited stream miles. Also, the current distribution of occupied
miles on the landscape differs from the historical distribution. The
range has contracted northward, Rio Grande cutthroat trout are now
restricted primarily to headwater streams, and the large connected
networks that once linked hundreds of stream miles together no longer
exist. The change in distribution is discussed briefly followed by a
discussion of fragmentation which has modified and curtailed habitat.
Historically, 43 percent of Rio Grande cutthroat trout populations
occupied streams 2,438 m (8,000 ft) or less in elevation (Alves et al.
2007, p. 18). Currently, only about 1.6 percent of the populations are
in streams less than 2,438 m (8,000 ft) (Alves et al. 2007, p. 18).
Conservation populations, as defined above, are now concentrated in
elevations from 2,743-3048 m (9,000-10,000 ft) (Alves et al. 2007, p.
18). High-elevation streams (above 2,743 m (9,000 ft)) are subject to
extreme and fluctuating environmental conditions including forest
fires, freezing, and dewatering (Novinger and Rahel 2003, p. 779). In
addition, headwater mountain streams often lack critical resources such
as deep pools (Harig and Fausch 2002, p. 546) and provide insufficient
refuge from catastrophic disturbance (Pritchard and Cowley 2006, p.
17). Because high-elevation headwater streams are narrow and small
compared to the larger downstream reaches that Rio Grande cutthroat
trout once occupied, the absolute loss of habitat in both quantity and
quality is greater than stream miles might indicate.
Historically, many watersheds supporting Rio Grande cutthroat trout
contained streams that were connected. For example, in Colorado, the
Trinchera, Conejos, Culebra, Costilla, and Alamosa rivers would all
have been connected through the upper Rio Grande, forming a vast
network of streams (Alves et al. 2007, p. 10). As a consequence of
habitat loss, each of these watersheds is now isolated from the other
and Rio Grande cutthroat trout are restricted to fragments of streams
(Alves et al. 2007, pp. 12, 29). Of the 120 conservation populations,
112 (representing 80 percent of occupied miles) are in isolated stream
fragments (Alves et al. 2007, p. 29). No populations are considered to
have strong connectivity (i.e., >= 5 connected streams with open
migration corridors) (Alves et al. 2007, pp. 29, 77). One population
has a moderate degree of connectivity (4 to 5 connected streams);
however, this watershed (Comanche Creek) is currently under restoration
and has very few fish present. Seven populations have very little
connectivity (2-3 connected streams, infrequent straying of adults may
occur) (Alves et al. 2007, pp. 29, 77). Because Rio Grande cutthroat
trout habitat is severely fragmented and because the effects of
fragmentation are considered one of the primary threats to Rio Grande
cutthroat trout populations, the consequences of fragmentation are
discussed in detail below.
Habitat fragmentation reduces the total area of habitat available,
reduces habitat complexity, and prevents gene flow (Saunders et al.
1991, p. 25; Rieman and McIntyre 1995, p. 293; Burkey 1995, pp. 527,
528; Dunham et al. 1997, pp. 1126, 1127; Frankham et al. 2002, p. 310;
Noss et al. 2006, p. 219). Fragmentation accelerates extinction,
especially when movement of fish among fragments is not possible, as is
the case with Rio Grande cutthroat trout (Burkey 1995, p. 540; Frankham
et al. 2002, p. 314). Isolated populations are vulnerable to extinction
through demographic stochasticity (random changes in the population
structure, e.g., uneven male/female ratios); environmental
stochasticity (random changes in the fishes' surroundings) and
catastrophes (e.g., fires, stream drying, freezing); loss of genetic
heterozygosity (genetic diversity) and rare alleles (inherited forms of
a genetic trait); and human disturbance (Shaffer 1987, p. 71; Rieman et
al. 1993, pp. 9-15; Burkey 1995, pp. 527, 528; Dunham et al. 1997, p.
1130; Frankham et al. 2002, pp. 310-324). Completely isolated fragments
are the most severe form of fragmentation
[[Page 27904]]
because the isolation prevents fish from mating with other fish
carrying different genes, thereby preventing new genes from entering
the isolated population (Frankham et al. 2002, p. 314). Of 120 Rio
Grande cutthroat trout conservation populations, 112 (93 percent, 80
percent of occupied miles) exist as isolated segments or have very
little connectivity (Alves et al. 2007, p. 29).
Apart from the isolation (lack of gene flow) that fragmentation
causes, the short length of the fragments and small population size
that they support are also of concern for Rio Grande cutthroat trout.
Seventy-one percent of Rio Grande cutthroat trout conservation
populations occupy stream segments of 8.1 km (5 mi) or less (median 6.2
km (4.2 mi)) (Alves et al. 2007, p. 26). Several researchers have found
that population viability of cutthroat trout is correlated with stream
length (Hilderbrand and Kershner 2000, p. 515; Young et al. 2005, p.
2405; Cowley 2007, DOI: 10.1002/aqc.845). Stream length is important
because trout need a variety of habitats to complete their life cycle
(i.e., spawning habitat, rearing habitat, adult habitat, refugial
habitat) (Rieman and McIntyre 1995, p. 293; Horan et al. 2000, p. 1251;
Harig and Fausch 2002, p. 546; Young et al. 2005, p. 2406). The shorter
the stream, the more likely it is that one or more of the Rio Grande
cutthroat trout's required habitats is either missing, or inadequate
for completion of the species life cycle (Hilderbrand and Kershner
2000, p. 513). This is particularly true in high-elevation streams
which are narrower and shallower than larger, lower elevation, streams.
The longer a stream is, the more complexity it encompasses and the
higher the probability that no particular habitat type limits the
population.
Hilderbrand and Kershner (2000, p. 515) estimated 8.3 km (5.1 mi)
were required to maintain a population of 2,500 cutthroat trout when
fish abundance was high (0.3 fish/m (0.09 fish/ft)). Adding a 10
percent loss rate, to account for emigration and mortality, increased
the length up to 9.3 km (5.8 mi) in order to maintain 2,500 fish. For
abundances of 0.2 fish/m (0.06 fish/ft) and 0.1 fish/m (0.03 fish/ft),
the corresponding length increased to 12.5 km (7.8 mi) and 25 km (15.5
mi), respectively (assuming no losses) (Hilderbrand and Kershner 2000,
p. 15). Young et al. (2005, p. 2405) found that to maintain a
population of 2,500 cutthroat trout, 8.8 km (5.5 mi) of stream were
needed. Cowley (2007 DOI: 10.1002/aqc.845) determined that in stream
widths of approximately 2 m (6.6 ft) (average width of most Rio Grande
cutthroat trout streams), a stream length of 11 km (6.8 mi) would be
needed to support a population of 2,750 fish. Because the majority (71
percent) of Rio Grande cutthroat trout conservation populations occur
in short stream fragments of 8.1 km (5 mi) or less, these studies
indicate that stream fragmentation (resulting in short stream lengths)
pose a threat to Rio Grande cutthroat trout conservation populations.
Longer streams support larger populations (Harig and Fausch 2002,
p. 546; Young et al. 2005, p. 2405). Population size is a major
determinant of species persistence (Reed et al. 2003, p. 23).
Population persistence decreases as population size decreases (Rieman
and McIntyre 1993, p. 15). Long-term persistence of a population
depends on having a sufficient number of individuals to avoid
inbreeding depression, which decreases population viability, and to
maintain genetic variation (Franklin 1980, pp. 135-148; Frankham et al.
2002, pp. 190-192; Reed 2005, pp. 563, 564). Genetic variability within
a population is necessary for adaptability (Reed 2005, p. 564; Cowley
2007 DOI: 10.1002/aqc.845). Genetic variation will be lost through time
in isolated populations and the loss occurs more quickly in small
populations than in large populations (Rieman and Allendorf 2001, p.
761). When a population is greatly reduced in size (bottlenecked),
genetic diversity is decreased (Frankham et al. 2002, p. 183)
In our previous status review (67 FR 39938), we concluded that a
population size of 2,500 fish would ensure long-term persistence of Rio
Grande cutthroat trout, i.e., would reduce the risks associated with
small population size alone. Since that time other peer-reviewed
literature has been published that allows us to further evaluate this
number. Reed et al. (2003, p. 30), in a review of 102 vertebrate
species, estimate that sufficient habitat should be present to allow
for approximately 7,000 breeding age adults in order to ensure long-
term species persistence. Cowley (2007 DOI: 10.1002/aqc.845) found that
a population size of 2,500 Rio Grande cutthroat trout failed to meet
the desired long-term effective population size (number of adults
actually contributing offspring to the population) of at least 500. A
minimum population size of 2,750 was sufficient if there was infrequent
loss of year classes (all the individuals of a population of fishes
born or hatched in the same year). He found that a larger population
size was required as survival rate of young fish (one year or less)
decreased. He concluded that managing for Rio Grande cutthroat trout
population sizes in the range of 8,000 to 16,000 would be more likely
to ensure population viability when there are low to intermediate
survival rates of young fish. While any population number we might use
to assess the status of the subspecies is unlikely to satisfy all
interested parties, we believe 2,500 continues to be a reasonable
standard by which to evaluate the populations. While the range of
acceptable standards may range from 2,500 to 16,000, there is relative
certainty that populations below 2,500 are likely at risk and may not
be contributing to long-term persistence of the subspecies.
In 2007, fifteen of the 120 conservation populations had 2,500-
7,000 Rio Grande cutthroat trout. The 120 conservation populations
occur in 161 individual streams. Several conservation populations
occupy multiple individual stream segments that are connected, thus the
numbers of occupied streams segments is larger than the total number of
conservation populations. Of those 161 individual streams, a minimum of
53 contain populations of under 500 reproducing adult fish. Because
population estimates are unavailable for 38 streams, and most of the 38
are short segments (2007 database), the total number of populations
with fewer than 500 reproducing adult fish is much likely greater than
53. Of the 99 conservation populations with quantitative estimates, 19
have an abundance of 0-0.03 fish/m (0-50 fish/mi) and 31 have an
abundance of 0.03-0.09 fish/m (50-150 fish/mi). These low abundances
indicate that on average, Rio Grande cutthroat trout need longer,
rather than shorter, stream segments to ensure their long-term
persistence because longer streams support larger numbers of fish
(Hilderbrand and Kershner 2000, p. 515).
In 2002, we identified 13 Rio Grande cutthroat trout populations as
secure (67 FR 39940). All 13 had populations over 2,500, contained no
nonnative trout, and were protected from invasion by nonnative fish by
a barrier. By 2007, 5 of these populations had fewer than 1,000 fish
and 3 others had fewer than 2,000. One of the populations
(approximately 13,000 fish in 2002) is thought to have been extirpated
by low water effects (the stream either dried or froze). Brown trout
were discovered above the barrier on one of the streams. The status of
only 5 populations remained unchanged between 2002 and 2007.
A ``general health assessment'' was used by Alves et al. (2007, pp.
41-43)
[[Page 27905]]
to look at the health of individual populations. Sixty-eight
populations (798 km (496 mi)) were judged to have a moderately high
degree of health, 50 (264 km (164 mi)) moderately low, and 1 (3.2 km (2
mi)) ranked as having low health (Alves et al. 2007, p. 42). Four
factors were considered in the assessment: isolation, temporal
variability (a measure of variability in the physical environment which
correlates with stream length), population size, and population
production (a composite score based on habitat condition, presence of
nonnatives, and disease) (Alves et al. 2007, pp. 82, 83, 89). These
factors were weighted in the following order: isolation (0.5), stream
length (0.7), population size (1.2), and population production (1.6).
The first 3 factors have a range of 1 to 4, while the last, population
production, has a range of 2 to 8 (Alves et al. 2007, p. 89),
effectively doubling its importance beyond the greater weighting (1.6)
assigned to it. Rationale for the weighting scheme is not provided.
Many scoring systems could be devised to determine population health
and it is unclear why isolation and stream length, two factors that
have been discussed extensively in conservation biology and cutthroat
trout conservation literature (e.g., Saunders et al. 1991, pp. 18-26;
Dunham et al. 1997, p. 1130; Hilderbrand and Kershner 2000, p. 513;
Frankham et al. 2002, Chapter 13; Young et al. 2005, p. 2405; Noss et
al. 2006, Chapter 7) were assigned the lowest weights. This rating
system is heavily biased towards production and does not provide a
balanced assessment of population health. However, even with this
unbalanced health assessment, only one stream ranked as having high
health, Comanche Creek. A major restoration of Comanche Creek began in
2007, and while we fully expect it to be restocked with nonintrogressed
Rio Grande cutthroat trout in the future, it has no Rio Grande
cutthroat trout currently.
It has been argued that small, isolated populations have persisted
for decades (Patten and Sloane 2007, p. 3). However, Rio Grande
cutthroat trout populations have only been monitored and intensively
managed during the last 50 years or less, and habitat conditions and
stressors are very different from historic conditions. Consequently,
long-term persistence cannot be appropriately assessed. In addition, as
Hilderbrand and Kershner state (2000, p. 517), although some isolated
populations may have persisted for centuries, these populations are
probably exceptions. To assume all isolated populations will behave
similarly may lead to insufficient protection (Hilderbrand and Kershner
2000, p. 517).
Based on the arguments presented above, we determined that stream
length, population size, and absence of nonnative trout are the most
important criteria by which to evaluate long-term population
persistence. We have evaluated the status of Rio Grande cutthroat trout
conservation populations primarily on stream length (9.6 km (6 mi) or
greater), population size (more than 2,500 fish), and presence or
absence of nonnative fish (Tables 1 and 2). All streams with a length
of over 9.6 km (6 mi) were initially evaluated. Stream miles in Tables
1 and 2 include all miles in the conservation population when more than
one stream is connected. Habitat condition and presence of a barrier
are also presented in Tables 1 and 2 because these factors are also
considered important in evaluating the status of the populations. Eight
streams (4 in Colorado, 3 in New Mexico, one shared) currently have
over 2,500 fish, are 9.6 km (6 mi) or longer, and have no nonnative
fish present (Table 1). In addition, the main stem of these streams is
greater than 1.5 m (5 ft) (although tributaries to the main stem may be
less than this width) and all have abundances of 151 fish per mile or
greater. Five of the streams, Cross, Medano, San Francisco, Canones,
and El Rito creeks, were identified as secure in 2002. Although these
eight streams meet the criteria, some have characteristics that are
less than optimal (Table 1). For instance, habitat quality in Cross and
Canones creeks is judged as ``Fair.'' In Canones Creek, the percentage
of pools (9 percent) is low and it was found to be at risk by Santa Fe
National Forest temperature standards (Ferrell 2006) (discussed in more
detail in the ``Climate Change'' section below).
Table 1.--Rio Grande Conservation Populations With Unaltered (< 1%) Genetic Status Occurring in Stream Lengths Greater Than 9.6 km (6 mi), With Greater
Than 2,500 Fish, and no Nonnative Trout Present
--------------------------------------------------------------------------------------------------------------------------------------------------------
Population Length in km
size (mi) Habitat condition Ownership State Barrier
--------------------------------------------------------------------------------------------------------------------------------------------------------
San Francisco Creek............... 3,820 23.5 (14.6) Excellent............ USFS, Private........ CO Water diversion.
Torcido Creek..................... 6,042 16.7 (10.4) Good................. Private.............. CO Drying.
Medano Creek...................... 5,795 33.6 (20.9) Excellent............ NPS, USFS............ CO None.
Cross Creek....................... 3,675 12.9 (8.0) Fair................. BLM, USFS, Private... CO None.
Costilla Creek.................... 5,200 21.1 (13.1) Excellent............ Private.............. NM, CO Temporary/Manmade.
Alamitos Creek.................... 3,080 11.4 (7.1) Good................. USFS................. NM Partial/Water
diversion.
El Rito Creek..................... 4,401 10.3 (6.4) Good................. USFS................. NM Temporary/Manmade.
Canones Creek..................... 3,683 9.7 (6.0) Fair................. USFS................. NM Waterfall.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2 shows all the other Rio Grande cutthroat trout conservation
populations in stream lengths greater than 9.6 km (6 mi). Six of the
populations have more than 2,500 Rio Grande cutthroat trout, but all of
these have nonnative brook trout present as well. In addition, 4 of
these have habitat quality judged as fair and one is in a stream with a
width less than 1.5 m (5 ft) wide, which puts it at risk for drying (as
discussed below). Abundance (fish per mile) is provided in Table 2
because some of these have less than 150 fish per mile, and, as
mentioned above, for populations with 0-50 or 50-150 fish per mile, a
longer stream length would be needed to ensure long-term persistence.
It should also be noted that Sangre de Cristo Creek has tested positive
for whirling disease. For all of these reasons, although the Rio Grande
cutthroat conservation populations presented in Table 2 occur in stream
lengths greater than 9.6 km (6 mi), all appear at risk for one or more
reasons. Two additional streams (Osier and Cascade) have strong
populations 3,239 and 2,372, respectively, with no nonnative trout
present. However, stream length for Osier Creek is only 5.9 km (3.7 mi)
and for Cascade it is 4.7 km (2.9 mi). While these populations do
currently contribute to the status of the subspecies range-wide, they
are considered too short to ensure long-term
[[Page 27906]]
persistence as their shorter length makes them more vulnerable to
extirpation from ash flow or other localized disturbance.
Table 2.--Rio Grande Conservation Populations in Stream Lengths Greater Than 9.6 km (6 mi), Sorted by Population Size. Nonnative Species May Be Present or Absent. BRK = Brook Trout, BRN =
Brown Trout, WS = White Sucker
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Abundance (fish per Length in km
Stream name Population size mile) (mi) Nonnatives present Habitat condition Width in feet State Barrier
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Jacks Creek...................... 4,849............... > 400............... 18.5 (11.5) BRK................. Fair............... < 5................ CO Drying.
Cabresto Creek................... 4,570............... > 400............... 13.7 (8.5) BRK................. Fair............... 5 to 10............ NM Diversion.
Sangre de Cristo Creek........... 3,793............... 151 to 400.......... 36.2 (22.5) BRK................. Fair............... 5 to 10............ CO Partial/Diversion.
South Carnero Creek.............. 3,748............... 151 to 400.......... 22.9 (14.2) BRK, BRN, WS........ Fair............... 10 to 15........... CO None.
West Indian Creek................ 3,345............... 151 to 400.......... 17.1 (10.6) BRK................. Excellent.......... 5 to 10............ CO Manmade dam.
Trinchera Creek.................. 2,941............... 151 to 400.......... 14.5 (9.0) BRK................. Excellent.......... 10 to 15........... CO None.
Polvadera Creek.................. 2,045............... 151 to 400.......... 12.1 (7.5) None................ Poor............... < 5................ NM Waterfall.
Jacks Creek...................... 1,504............... 151 to 400.......... 11.3 (7.0) None................ Good............... 5 to 10............ NM Temporary/Manmade.
Jim Creek........................ 1,283............... 151 to 400.......... 10.0 (6.2) BRK................. Poor............... 5 to 10............ CO None.
Ute Creek........................ 1,260............... 50 to 150........... 13.8 (8.6) None................ Good............... 5 to 10............ NM None.
Rio de Truchas................... 692................. 50 to 150........... 10.5 (6.5) None................ Fair............... 5 to 10............ NM Diversion.
Little Vermejo Creek............. 680................. 50 to 150........... 11.9 (7.4) BRK................. Excellent.......... 5 to 10............ NM Temporary/Manmade.
Vallejos Creek................... 678................. 50 to 150........... 11.7 (7.3) BRN................. Good............... 10 to 15........... CO None.
Cave Creek....................... 411................. 50 to 150........... 10.1 (6.3) BRK, BRN, WS........ Fair............... 5 to 10............ CO None.
East Pass Creek.................. 369................. 50 to 150........... 11.1 (6.9) None................ Fair............... < 5................ CO Drying.
Middle Carnero Creek............. 344................. < 50................ 11.3 (7.0) WS.................. Fair............... < 5................ CO Manmade dam.
Ricardo Creek.................... 271................. 50 to 150........... 14.5 (9.0) BRK................. Good............... 5 to 10............ CO Temporary/Manmade.
Torsido Creek.................... 250................. 50 to 150........... 10.3 (6.4) BRK................. Poor............... < 5................ CO None.
Wagon Creek...................... 246................. 151 to 500.......... 20.9 (13.0) BRK................. Good............... 5 to 10............ CO Partial/Diversion.
McCrystal Creek.................. 236................. < 50................ 15.1 (9.4) None................ Good............... 5 to 10............ NM Temporary.
South Ponil Creek................ 202................. < 50................ 15.3 (9.5) None................ Good............... 5 to 10............ NM Temporary/Manmade.
Rio de Oso....................... 194................. < 50................ 12.4 (7.7) None................ Fair............... < 5................ NM None.
Capulin Creek.................... 186................. < 50................ 11.9 (7.4) None................ Excellent.......... 5 to 10............ NM Drying.
North Fork Carnero Creek......... 97.................. < 50................ 13.0 (8.1) WS.................. Fair............... < 5................ CO Manmade dam.
Cat Creek........................ Unknown............. Unknown............. 15.1 (9.4) None................ Fair............... < 5................ CO Drying.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Habitat fragmentation is a threat that can be partially alleviated
by management activities. Three major watershed-scale projects have
been initiated on both private and USFS lands and are in various phases
of implementation. A joint project between Vermejo Park Ranch and the
states of Colorado and New Mexico to restore the Costilla Creek
watershed began in 2002 (Patten et al. 2007, pp 95-102). The
restoration removed brook trout, brown trout, and introgressed
cutthroat trout and reintroduced Rio Grande cutthroat trout into
Costilla Creek, 2 tributaries, and 3 small lakes, totaling 22 km (13.6
miles) of stream and 9.5 ha (23.5 ac) of lake (project is discussed
further in the ``Fisheries Management'' section below). As part of the
larger Costilla Project, 34 km (21.1 mi) of Comanche Creek and selected
tributaries were chemically treated with piscicides (chemicals that
kill fish) in 2007. Most likely a second treatment will be required and
will be completed in 2008 before Rio Grande cutthroat trout are stocked
back into the watershed. A draft Candidate Conservation Agreement with
Assurances with private landowners has been drafted so that the
Costilla Creek project can be extended downstream. Successful
implementation of this project would lead to the restoration of
approximately 241 km (150 mi) and 25 lakes (Patten and Sloane 2007, p.
7). The Placer watershed in Colorado also underwent chemical treatment
in 2007. This watershed has the potential for approximately 80.5 km (50
mi) of connected stream. If successful, the Costilla and Placer
watersheds would represent substantial gains in the goal of creating
connected stream systems for Rio Grande cutthroat trout.
While watershed restoration can reconnect streams and is the best
method for addressing fragmentation, major restoration projects face
many challenges including: negative public sentiment towards using
piscicides in streams which slows or stops projects (Patten et al.
2007, p. 102), incomplete treatment which leaves nonnatives present,
sabatoge of the treatment area (unauthorized introduction of nonnative
trout) (Japhet et al. 2007, p. 17), subsequent barrier failure which
allows nonnatives to reinvade a system (Japhet et al. 2007, p. 15), and
inadvertent mistakes. While many stream segments have been restored and
the Costilla and Placer watershed projects are in progress, no major
watershed restorations have been completed.
The Service has evaluated the data presented by Alves et al. (2007)
and supplemental information requested related to the database. Based
on our knowledge of Rio Grande cutthroat trout populations that we
previously classified as secure in 2002, and all of the information
available to us we conclude:
(1) The majority of Rio Grande cutthroat trout populations (93
percent) are in isolated fragments less than 8 km (5 mi) long (71
percent);
(2) Populations are concentrated in high elevation (2,438 to 3,048
m (8,000 to 10,000 ft)) headwater streams that provide marginal
habitat, especially in regards to the number and depth of pools
critical for trout survival in times of environmental extremes;
(3) The drought in the early 2000s had resulted in adverse effects
on several populations (discussed in more detail in the ``Climate
Change'' section below);
(4) Eight of 13 populations we had identified as secure in 2002
would no
[[Page 27907]]
longer meet the criteria we used at that time (67 FR 39937); and
(5) Only eight populations currently meet our revised criteria for
long-term persistence.
Although additional populations may have greater than 2,500 fish or are
in streams longer than 9.6 km (6 mi), there are additional significant
threats to those populations that put their long-term persistence in
question. For these reasons, we find that Rio Grande cutthroat trout is
threatened by fragmentation, isolation, and loss of habitat throughout
its range. While watershed restoration may alleviate this threat in the
future, insufficient progress has been made to alleviate the threat of
fragmentation range-wide at this time.
Habitat Condition
Many Rio Grande cutthroat trout conservation populations currently
occupy lands administered by Federal agencies. Of the total 1,110 km
(690 mi) of occupied habitat, 698 km (434 mi) (63 percent) are under
Federal jurisdiction, with the majority (59 percent) occurring within
National Forests (Alves et al. 2007). Rio Grande cutthroat trout occupy
6.1 km (3.8 mi) of land administered by the BLM, 30.5 km (19 mi)
managed by the National Park Service, and 397 km (247 mi) that are
owned privately.
Land uses associated with each conservation population were
identified in Alves et al. (2007, p. 49, Table 33), but the impact of
the activities was not evaluated in relation to individual populations
or the conservation of the subspecies. Non-angling recreation (e.g.,
camping, hiking, ATV use, etc.) occurs in 90 percent of the
conservation populations, and angling occurs in 84 percent of the
conservation populations. Livestock grazing occurs within the zone of
influence (area around the stream in which activities influence stream
habitat) of 87 percent of the conservation populations, roads in 58
percent, timber harvest in 19 percent, dewatering in 17 percent, and
mining in 3 percent. Only 3 populations (3 percent) were judged as
having no land use activities within a zone that would influence the
stream habitat. Many populations have more than one land use occurring
in the area.
An evaluation of habitat quality was conducted for currently
occupied habitat (Alves et al. 2007, p. 20). The evaluation considered
both natural habitat features and human disturbances, including land
use practices. A stream ranked excellent if it had ample pool habitat,
low sediment levels, optimal temperatures, and quality riparian
habitat. Good habitat quality had some attributes that are less than
ideal, and fair habitat has a greater number of attributes that are
less than ideal. Poor habitat quality is found where most habitat
attributes reflect inferior conditions. Approximately 224 km (139 mi)
(20.2 percent of occupied habitat) received an excellent habitat
rating. Good habitat conditions were found in 426 km (265 mi) of
habitat (38.4 percent of occupied habitat), and fair habitat conditions
were found in 335 km (208 mi) of habitat (30.1 percent of occupied
habitat). Poor conditions were found in 35 km (22 mi) (3.2 percent of
occupied habitat), and habitat conditions in 90 km (56 mi) (8.1
percent) were unknown (Alves 2007, p. 2). The majority of occupied
habitat (58.6 percent) is considered in good or excellent condition
(Alves et al. 2007, p. 20).
The Service also reviewed 19 detailed stream survey reports which
were conducted by the Santa Fe and Carson national forests in the
period 2001-2006. Although these surveys represent only about one
quarter of the conservation populations in New Mexico (19 of 84
populations), both large (i.e., Pecos River, Rio de las Vacas, Comanche
Creek) and small (i.e., Yerba, Manzanita creeks) streams are
represented. Therefore, these surveys provide additional insight into
the habitat condition on USFS lands. Of the 19 streams surveyed, the
most consistent problem is lack of pool habitat. Of the 19 streams, 18
had less than the 30 percent pool habitat (range 1-21 percent) needed
to be considered properly functioning trout streams. For eight of these
streams, a target value of 30 percent pool habitat was not considered
appropriate because they were 1st or 2nd order streams (i.e., headwater
streams) which often have few pools naturally because they occur on
high gradient slopes. But for four of these eight streams, the pool
habitat ranged from 1-3 percent and the reports noted that even for
headwater streams this was an insufficient number of pools.
In most streams (16 of 19) the average residual pool volume, which
represents initial pool depth if the stream were to dry, met the USFS
standard of 0.3 m (1 ft) or greater. However, the deepest average
residual pool volume was only 0.67 m (2.2 ft) and the mean depth of
pools for all 19 streams was 0.39 m (1.3 ft), indicating that the
majority of pools are relatively shallow.
Pools are recognized as important overwintering habitat and also
are holding areas for trout when streams dry. Not only are the number
of pools consistently fewer than desirable, but they are also
relatively shallow, and thus provide limited refugial habitat in times
of stream freezing or drying. Lack of deep pools could affect year-
class survival. As noted by Cowley (2007 DOI: 10.1002/acq.845) loss of
a year class of fish would suggest that longer stream length is needed
to provide adequate habitat for long-term population persistence.
However, as mentioned above, the sample size (19 streams) is relatively
small and it is not known if the results accurately represent Rio
Grande cutthroat trout streams range-wide.
Livestock grazing occurs in the vicinity of 87 percent of the Rio
Grande cutthroat trout populations (Alves 2007, p. 49). We recognize
that improper grazing does cause adverse impacts (e.g., loss of cover,
increased sedimentation, loss of riparian vegetation) to some
individual populations of Rio Grande cutthroat trout, especially during
drought conditions when the cattle tend to concentrate in riparian
areas. While a few of the USFS stream surveys noted that impacts by
cattle (or elk) were causing localized problems, grazing was not cited
as causing damage throughout the length of any stream. Specific
information on grazing impacts to Rio Grande cutthroat trout habitat on
a range-wide basis is not available. We have no information that leads
us to conclude that improper grazing is a significant threat to Rio
Grande cutthroat trout range-wide.
Timber harvest and associated road building has also led to the
deterioration of Rio Grande cutthroat trout habitat. However, timber
harvest in the National Forests has declined appreciably in the last 20
years. As an example, on the two forests in New Mexico that have
conservation populations, the Santa Fe National Forest and Carson
National Forest, there has been a total of 3.2 ha (8 ac) clear cut
since 1995 (Fink 2008 pp. 2, 3). The average amount of timber cut per
year from 1984 to 1994 in these forests was 27.6 and 19 million board
feet (MBF), respectively. From 1995 to 2005, the average amount cut per
year was 3.5 and 0.09 MBF, respectively (Fink 2008, pp. 2, 3). While
the effects of past logging practices may still be evident on the
landscape in some locations, we conclude that timber harvest is not
currently a threat to Rio Grande cutthroat trout populations.
Roads and off-road vehicles can have negative impacts on stream
habitat primarily through increased sedimentation which degrades
spawning habitat. Non-angling recreation (which includes hiking and
camping as well as off-road vehicle use) is present near 90 percent of
the
[[Page 27908]]
conservation populations. On November 9, 2005, the USFS published
revised rules regarding travel management on their lands (70 FR 68264).
One of the primary purposes of the rule is to protect natural
resources. The final rule requires the designation of roads, trails,
and areas that are open to motor vehicle use by class of vehicle and,
if appropriate, time of year. Use of motor vehicles off designated
routes will be prohibited (70 FR 68264). The Service has begun
consultation on the Travel Management Plans proposed by National
Forests in USFS Region 3 (Arizona and New Mexico) and protecting
aquatic resources is an important component of these plans. While roads
have been identified as an area of concern for some streams (e.g., Tio
Grande, Rio Grande del Rancho, Martinez 2001, 2002), we conclude that
roads are not a threat to Rio Grande cutthroat trout populations range-
wide.
Management agencies are actively working towards improving habitat
conditions for Rio Grande cutthroat trout. In addition to the travel
management rule on USFS lands, several projects have been completed
recently to address habitat degradation caused by roads. For example,
grant money was obtained and used to inventory and identify 97 road
improvement projects to reduce sediment input into Comanche Creek
(Martinez 2006, p. 5). Six culverts were installed or realigned and ten
sediment traps and energy dissipaters were installed below culvert
spillways. Culverts that drained directly into Comanche Creek were
removed. Abandoned logging roads were stabilized and unneeded roads
were re-contoured to natural slope and re-vegetated (USFS 2006, pp.18-
19). In 2006, on the Santa Fe National Forest, over 1,829 m (6,000 ft)
of buck and pole fence was constructed to improve traffic control and
enforce an off-road vehicle closure around Rio Cebolla. Approximately
17.7 km (11 mi) of stream and riparian habitat was protected by this
project (USFS 2006, p. 12). On the Rio Grande National Forest, road-
stream crossing inventories and assessments were conducted for all
streams with conservation populations to determine if the culverts were
barriers to fish (USFS 2006, p. 4). Most of the 120 conservation
populations (90 percent) have one or more restoration, conservation, or
management activities either completed or currently being implemented
(Alves et al. 2007, p. 60).
Range-wide habitat quality is still difficult to accurately assess.
Although an insufficient amount of pool habitat exists on the majority
of streams sampled by the USFS in New Mexico, we cannot draw the same
conclusion range-wide at this time because of lack of data. Alves et
al. (2007 database) did not identify a lack of pools as a systematic
problem. While land management practices have clearly improved and have
less direct impact on Rio Grande cutthroat trout streams, some streams
are still recovering from past land management practices. Therefore we
conclude that there is insufficient information to indicate that
habitat quality currently is a significant threat to Rio Grande
cutthroat trout rangewide.
Nonnative Species
The introduction of nonnative trout is widely recognized as one of
the leading causes of range reduction in cutthroat trout subspecies
(Griffith 1988, pp. 134, 137; Lassuy 1995, p. 394; Henderson et al.
2000, pp. 584, 585; Dunham et al. 2002, p. 374; Peterson et al. 2004,
p. 769). Dunham et al. (2004) provide an overview of the impact of
nonnatives on headwater systems in North America. Since the late 1800s,
fishery managers introduced nonnative salmonids (trout and salmon
species) into lake and stream habitats of Rio Grande cutthroat trout.
Nonnative rainbow, brook, brown trout and Yellowstone cutthroat trout
have been introduced extensively throughout the range of Rio Grande
cutthroat trout, and they compete (brook and brown trout) and hybridize
(rainbow and other cutthroat subspecies) with Rio Grande cutthroat
trout. Forty-six of 120 conservation populations (38 percent) have
nonnative trout present (2007 database). When Rio Grande cutthroat
trout occur in the same stream as nonnative trout, Rio Grande cutthroat
trout typically occupy the colder, headwater reaches and the nonnative
trout occupy areas downstream (Griffith 1988, p. 135; Dunham et al.
1999, p. 885).
Competition from nonnative trout, especially brook trout, is
recognized as a threat to Rio Grande cutthroat trout (Behnke 2002, p.
147; Peterson et al. 2004, pp. 768, 769). When brook trout invade
streams occupied by cutthroat trout, the native cutthroat trout decline
or are displaced (Griffith 1988, p. 136; Harig et al. 2000, pp. 994,
998, 999; Dunham et al. 2002, p. 378; Peterson et al. 2004, p. 769;
Young and Guenther-Gloss 2004, p. 193; Fausch et al. 2006, p. 6). Brook
trout are the most common nonnative trout sympatric (co-occurring) with
Rio Grande cutthroat trout populations in Colorado (2007 database).
Brook trout reduce recruitment of cutthroat trout and reduce inter-
annual survival of juveniles, leading to a reduction in population size
(Peterson et al. 2004, p. 769). Experiments where brook trout were
removed from cutthroat trout populations showed an increase in the
survival of juvenile cutthroat trout (Peterson et al. 2004, p. 767).
Paroz (2005, p. 22) found that mean density and relative weight of Rio
Grande cutthroat trout were lower in populations sympatric with brook
trout. Several Rio Grande cutthroat trout conservation populations have
been identified as at risk and declining because of brook trout (Alves
et al. 2002, pp. 1-4).
In New Mexico, brown trout is the most common nonnative trout
present in Rio Grande cutthroat trout conservation populations
(summarized from 2007 database). Not only are brown trout piscivores
(feed on other fish), but they have also been shown to compete with Rio
Grande cutthroat trout for resources such as food and space. Research
has shown that Rio Grande cutthroat trout confined with brown trout
grew significantly less, while the brown trout grew significantly more,
than control fish (Shemai et al. 2007, pp. 315, 320, 321). A similar
result was seen in experiments conducted with Bonneville cutthroat
trout and brown trout (McHugh and Budy 2005, p. 2788). These results
indicate that brown trout represent a threat to Rio Grande cutthroat
trout from competition as well as predation (Paroz 2005, p. 34).
The primary threat to Rio Grande cutthroat trout from rainbow trout
and other cutthroat trout subspecies is through hybridization and
introgression (Rhymer and Simberloff 1996, pp. 83, 97). The genetic
distinctiveness of Rio Grande cutthroat trout can be lost through
hybridization (Allendorf et al. 2004, p. 1205). Of the 120 conservation
populations, 95 (79 percent) range-wide have been tested and are less
than 1 percent introgressed (Alves et al. 2007, p. 31). These
nonintrogressed populations occupy 870 km (541 mi), or 78 percent, of
the 1110 km (690 mi) occupied by conservation populations (Alves et al.
2007, p. 31). Another 161 km (100 mi) are occupied by populations that
are 90-99 percent genetically pure, and 104 km (65 mi) are occupied by
populations that have not been tested but are connected to
nonintrogressed populations and have no record of stocking (Alves et
al. 2007, p. 34).
To minimize the contact of nonnative trout with Rio Grande
cutthroat trout, barriers have been constructed where natural barriers
didn't already exist in order to prevent nonnatives from invading.
Alves et al. (2007, pp. 35, 36)
[[Page 27909]]
rated the genetic risk to the 120 conservation populations. A
combination of barrier condition or presence and distance to
hybridizing species, determined if a population was at moderate or low
risk (Alves et al. 2007, p. 80). Populations protected by a complete
barrier fell into the no risk category. They determined that 80 had no
risk of genetic mixing with nonnative trout, 32 were at moderate risk,
and 4 were at low risk. As mentioned earlier, four populations that
Alves et al. (2007, pp. 35, 36) consider conservation populations are
sympatric with a hybridizing species, and, therefore, we consider them
at high risk.
Since 2002, NMDGF and CDOW visited approximately 40 and 50 Rio
Grande cutthroat trout conservation populations, respectively, to
assess barrier presence and condition. Seven new barriers have been
installed since 2002, and maintenance was done on at least eight
(Japhet et al. 2007, pp. 24, 25; Patten et al. 2007, pp. 6, 11, 12, 16,
17, 53). Both agencies have also mechanically and chemically removed
nonnative trout from Rio Grande cutthroat trout streams. NMDGF removed
nonnatives from 11 streams, and CDOW removed them from two (Patten and
Sloane 2007, p. 5; Japhet et al. 2007, p. 26).
Since 2002, CDOW and NMDGF have also proactively pursued genetic
testing of Rio Grande cutthroat trout populations using the best
technologies available. In many instances, the results confirmed
previous assessments of genetic purity, while in other cases
populations were either upgraded or downgraded (Japhet et al. 2007, pp.
46-47; Patten et al. 2007, pp. 43-45). Diagnostic markers for
Yellowstone cutthroat trout were also identified, which has led to more
refined testing and more confidence in the categorization of the
populations. The most recent results were used in the 2007 database.
Results of the testing can be found in peer-reviewed literature (e.g.,
Pritchard et al. 2007a, Pritchard et al. 2007b) and in reports to the
States (e.g., Pritchard and Cowley 2005).
Approximately 38 percent of Rio Grande cutthroat trout conservation
populations co-occur with nonnative trout (2007 database). Competition,
predation, and hybridization with nonnative trout are considered an
important source of stress that can depress Rio Grande cutthroat trout
population numbers or, under the right circumstances, displace them
(Fausch et al. 2006, pp. 9, 10). Although resource agencies remove
nonnative trout through electrofishing when they co-occur with
cutthroat trout subspecies, seldom if ever is complete removal possible
(Patten et al. 2007, p. 104). Peterson et al. (2004, p. 769) show that
over 90 percent of the brook trout population must be removed each year
for 3 consecutive years to allow a large cohort of Colorado River
cutthroat trout to survive from age 0 to age 2. This level of effort
has not been documented for stream segments occupied by Rio Grande
cutthroat trout populations (e.g., Japhet et al. 2007, p. 26).
The Service concludes that nonnative fish are a threat to Rio
Grande cutthroat trout range-wide based on the following facts:
(1) Approximately 38 percent of the conservation populations have
nonnative trout present;
(2) Nonnative fish are a documented threat to Rio Grande cutthroat
trout populations;
(3) Mechanical removal cannot remove all of the nonnative fish;
(4) The level of effort required to reduce brook trout populations
to levels sufficient for survival of young Rio Grande cutthroat trout
is not currently being conducted; and,
(5) The number of streams that need regular treatment exceeds the
capability of resource managers at their current staffing levels.
Drought
The relatively short-term drought of the early 2000s negatively
impacted or extirpated 14 Rio Grande cutthroat trout populations in
Colorado and New Mexico (Japhet et al. 2007, pp. 42-44; Patten et al.
2007, pp. 14-40). A fifteenth population is thought to have been
extirpated in 2006 by complete freezing caused by low flow in the
winter (Ferrell 2006, p. 11). The number of streams impacted may have
been greater, because managers only survey a fraction of the 120
conservation populations in any given year.
We assume that small streams (1.5 m (5 ft) wide or less) are more
susceptible to drying, increased water temperatures, and freezing than
larger ones and that stream width is an indicator of risk. Decreased
stream flow reduces the amount of habitat available for aquatic
species, and water quality (e.g., temperature, dissolved oxygen) may
become unacceptable in declining flow. Approximately 27 conservation
populations are in streams that are 1.5 m (5 ft) or less in width
throughout their entire length (2007 database). An additional 29 stream
segments that are tributaries to the conservation populations are also
less than 1.5 m (5 feet) in width (2007 database). Although not all
small streams have equal risk, small headwater streams, especially
those with an inadequate number of deep pools, are most likely to lose
suitable habitat. Even if streams do not dry (or freeze) completely,
stream length can be truncated during drought and many fish can perish,
greatly reducing the population number (bottleneck) and reducing
genetic diversity (Frankham et al. 2002, p. 183).
Because of the documented extirpation and population reductions of
Rio Grande cutthroat trout caused by drought, the possibility of more
widespread drought accompanying climate change, and the lack of a
range-wide plan to address drought, we conclude that drought is a
threat to Rio Grande cutthroat trout throughout its range (discussed in
``Climate Change'' section below).
Fire
Wildfires are a natural disturbance in forested watersheds.
However, since the mid-1980s, wildfire frequency in western forests has
nearly quadrupled compared to the average frequency during the period
1970-1986. The total area burned is more than six and a half times the
previous level (Westerling et al. 2006, p. 941). In addition, the
average length of the fire season during 1987-2003 was 78 days longer
compared to that during 1970-1986 and the average time between fire
discovery and control was 29.6 days longer (Westerling et al. 2006, p.
941). Westerling et al. (2006, p. 942) found that wildfire sensitivity
was related to snowmelt timing with 56 percent of fires and 72 percent
of burned area occurring in early snowmelt years. Early spring snowmelt
is strongly associated with spring temperature (Stewart et al. 2004, p.
218; Westerling et al. 2006, p. 942). Westerling et al. (2006, p. 942)
conclude that there are robust statistical associations between
wildfire and climate in western forests and that increased fire
activity over recent decades reflects responses to climate change
(discussed further in the ``Climate Change'' section below).
In the Southwest, the fire season is followed by the monsoon season
(July to August). Consequently, denuded watersheds are susceptible to
heavy precipitation leading to severe floods and ash flows. Although
fish may survive the fire, ash and debris flows that occur after a fire
can eliminate populations of fish from a stream (Rinne 1996, p. 654;
Brown et al. 2001, p. 142; USFS 2006, p. 32; Patten et al. 2007, p.
33), and the fire suppression activities (e.g., fire retardant, water
removal, road construction) may also impact stream ecosystems (Buhl and
Hamilton 2000, pp. 410-416; Backer et al. 2004, pp. 942,
[[Page 27910]]
943). Wildfires within the range of Rio Grande cutthroat trout have
impacted or eliminated fish populations (Japhet et al. 2007, p. 20;
Ferrell 2006, p. 32; Patten et al. 2007, pp. 33, 36), and the effects
of large fires are recognized as a threat to greenback cutthroat
(Oncorhynchus clarki stomias) populations in Colorado (Young and
Guenther-Gloss 2004, p. 194). Imperiled fish populations can be rescued
if ash flows are imminent, but a rescue and evacuation plan should be
in place (e.g., Brooks 2004, pp. 1-15).
Dunham et al. (2007, p. 342) found significantly elevated stream
temperatures for at least a decade after a stand-replacing wildfire
because of the lack of stream shading. In addition, the authors suggest
that longer term (over 20 years) increases in stream temperatures are
likely in systems where debris flows or severe floods completely
eliminate streamside vegetation and reorganize the channel. Rainbow
trout were found to be resilient and recolonized the burned streams
within 1 year of extirpation in spite of elevated water temperatures
(Dunham et al. 2007, p. 343). Dunham et al. (2003a, pp. 188, 189)
suggest that fire poses a greater threat to fish populations when
habitat is fragmented. Moyle and Light (1996, p. 157) argue that
habitat degradation favors nonnative fishes and that species with
narrow habitat requirements are expected to be more sensitive to
habitat alteration caused by fire than generalist species such as
rainbow trout (Dunham et al. 2003a, p. 189).
Fire risk can be reduced through fuels reduction and prescribed
burns. The National Forests in New Mexico have active programs to
improve forest health. As an example, 28,314 ha (69,965 ac) have
undergone fuel-reduction treatment, thereby improving watershed
conditions associated with 100 km (62 miles) of stream, and an
additional 58,912 ha (145,575 ac) are planned for treatment to improve
conditions associated with an additional 128 km (79.5 mi) of stream
(Ferrel 2002, p. 12). Such techniques have been found to reduce fire
severity even under extreme weather conditions in low-elevation
ponderosa pine forests (Schoennagel et al. 2004, p. 669). However, for
mid-elevation, mixed-severity fire regimes, fuel-reduction treatments
had virtually no effect on the 2002 Hayman Fire (Colorado), and extreme
climate can override the influence of stand structure and fuels on fire
behavior (Schoennagel et al. 2004, pp. 672, 673). Climate variation,
not fuel levels, is seen as the dominant influence on fire frequency
and severity in subalpine forests (Schoennagel et al. 2004, p. 666).
Wildfires that eliminate nonnative fish provide the opportunity to
reclaim streams for Rio Grande cutthroat trout. The 1996 Dome Fire in
the Jemez Mountains (Santa Fe National Forest) extirpated the fish
residing in Capulin Canyon. In 2006, after 10 years of habitat
recovery, 100 Rio Grande cutthroat trout from Canones Creek were
stocked into Rio Capulin adding 11.2 km (7.0 mi) of occupied habitat in
New Mexico (Patten et al. 2007, p. 94). In addition, ash flows after
the 2004 Peppin Fire in the Capitan Wilderness (Lincoln National
Forest) apparently eliminated all fish from Pine Lodge Creek and
Copeland Creek (Patten et al. 2007, pp. 255-258), and there are plans
to restore Rio Grande cutthroat trout into these streams. Restoration
of Pine Lodge Creek would add approximately 4 km (2.5 mi) of habitat in
the Pecos Headwaters GMU (Patten et al. 2007, p. 255).
Although we recognize that Rio Grande cutthroat trout evolved in a
landscape that included fire, wildfire intensities and size are likely
changing because of increased fuel loads and possibly climate change
(see ``Climate Change'' section below). Wildfire today is much more of
a threat than it was historically to Rio Grande cutthroat trout because
of existing habitat loss, fragmentation, and climate change. These
multiple stressors may overwhelm the subspecies' resilience to
disturbance such as fire (Rieman et al. 2005, pp. 2, 3). Although fire
may also provide opportunity for repatriation of Rio Grande cutthroat
trout by eliminating nonnative fish, total elimination of nonnative
fish from fire-affected streams is not guaranteed, and it may take many
years for the habitat to become suitable. For these reasons, we
conclude that wildfire is a significant threat to Rio Grande cutthroat
trout throughout its range.
Summary of Factor A
In summary, Rio Grande cutthroat trout populations have been and
continue to be impacted by habitat fragmentation and isolation,
nonnative species interactions, drought, and fire. Rio Grande cutthroat
trout conservation populations occupy a fraction of their historical
habitat, they are confined primarily to small high-elevation streams
with marginal habitat, they are highly fragmented, and the stream
segments they occupy are short in length. All of these factors work to
reduce gene flow between populations and reduce the ability of
populations to recover from catastrophic events thus threatening their
long-term persistence. Detailed habitat surveys, although not available
range-wide, are uniformly consistent in documenting a lack of pools in
streams occupied by Rio Grande cutthroat trout. Deep pools are
considered a critically important element of Rio Grande cutthroat trout
habitat. As discussed above, in order to ensure some level of
population stability and contribute to the long-term persistence of the
subspecies, populations should consist of more than 2,500 fish, occupy
9.6 km (6 mi) of stream or more, and have no nonnative trout present.
Currently, only eight Rio Grande cutthroat trout populations meet these
criteria. Nonnative trout co-occur with 38 percent of Rio Grande
cutthroat trout conservation populations. Because of the documented
negative impacts of nonnative trout on cutthroat trout discussed above,
nonnatives are an ongoing threat to the security of Rio Grande
cutthroat trout. Additionally, although drought and fire have impacted
a limited number of populations since the last status review, negative
impacts from these two factors may increase in response to climate
change (as discussed in the ``Climate Change'' section below). Based on
the best scientific and commercial information available to us, we
conclude that the present or threatened destruction, modification, or
curtailment of its habitat or range is a threat to the continued
existence of Rio Grande cutthroat trout.
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
No commercial harvest occurs for Rio Grande cutthroat trout.
Recreational angling occurs on approximately 84 percent of the
populations (Alves et al. 2007, p. 49). Fishing regulations in New
Mexico and Colorado appropriately manage recreational angling. For
example, many of the streams with Rio Grande cutthroat trout are
``catch and release.'' Those that are not have a 2 (New Mexico) or 4
(Colorado) fish limit. Many of the streams with pure populations of Rio
Grande cutthroat trout are remote and angling pressure is light. For
these reasons, angling is not considered a threat to Rio Grande
cutthroat trout.
Scientific collection of Rio Grande cutthroat trout for scientific
or educational purposes is controlled by a strict permitting process
that prevents excessive sampling. In addition, advancements in
molecular technology have resulted in the need for only a small
clipping from a fin to provide sufficient material to perform molecular
[[Page 27911]]
analysis of genetic purity. To test for whirling disease (see
``Disease'' section below for further discussion), usually 60 fish are
collected and sacrificed. However, to minimize the collection of Rio
Grande cutthroat trout during whirling disease testing, nonnative trout
are collected preferentially over Rio Grande cutthroat trout, or sample
sites are selected below a barrier that protects a population of Rio
Grande cutthroat trout from nonnative trout. In some situations fewer
than 60 Rio Grande cutthroat trout will be collected and sacrificed for
testing. For these reasons, overutilization for scientific purposes is
not considered a threat to Rio Grande cutthroat trout.
Summary of Factor B
Because no commercial harvest occurs for Rio Grande cutthroat
trout, fishing regulations in New Mexico and Colorado minimize the
impact of recreational angling, and scientific collection of Rio Grande
cutthroat trout for scientific or educational purposes is controlled by
a strict permitting process that prevents excessive sampling, we
conclude that the best scientific and commercial information available
to us indicates that Rio Grande cutthroat trout is not threatened by
overutilization for commercial, recreational, scientific, or
educational purposes.
C. Disease or Predation
Disease
Whirling disease is of great concern to fishery managers in western
States. Whirling disease is caused by the nonnative myxosporean
parasite, Myxobolus cerebralis. This parasite was introduced to the
United States from Europe in the 1950s and requires two separate hosts,
a salmonid fish and an aquatic worm (Tubifex tubifex) to complete its
life cycle. Spores of the parasite are released from infected fish when
they die. The spores are ingested by T. tubifix where they undergo
transformation in the gut to produce actinosporean triactionomyxons
(TAMs). Trout are infected either by eating the worms (and TAMs) or
through contact with water in which TAMs are present.
The myxosporean parasite became widely distributed in Colorado in
the early 1990s through the stocking of millions of catchable size
trout from infected hatcheries (Nehring 2007, p. 1). Up to 2001, it was
estimated that whirling disease infection had negatively impacted
recruitment of wild rainbow and brook trout fry (small recently emerged
fish) in 560-600 km (350-400 mi) of stream in Colorado (Nehring 2007,
p. 2). In 2006, the number of sites that tested positive for whirling
disease was considerably higher than in any of the previous field
seasons (Nehring 2007, p. 11). Whirling disease is also present in
several streams in New Mexico (67 FR 39943, Patten and Sloane 2007, p.
11). Laboratory (DuBey et al. 2007, pp. 1411, 1412) and field (Thompson
1999, pp. 323-325) experiments have shown that Rio Grande cutthroat
trout is very susceptible to whirling disease.
Among the four lineages (I, III, V, and VI) of T. tubifix known to
occur in Colorado, New Mexico, and other states, lineage III is the
only one susceptible to infection by M. cerebralis (DuBey and Caldwell
2004, p. 183; Nehring 2007, p. 11). Because T. tubifix is typically
found in degraded habitat with higher levels of sediment and warmer
temperatures, it had been hypothesized that Rio Grande cutthroat trout
were provided some level of protection because they occur in high-
elevation cold-water streams (67 FR 39943). Extensive sampling of
tubificid worms in Colorado does not support this hypothesis. Nehring
(2007) collected tubificid worm samples from over 100 sites in
Colorado, including streams occupied by Rio Grande cutthroat trout. He
stratified his results by 305 m (1,000 ft) elevation groups from 1829 m
(6,000 ft) to 3657 m (12,000 ft) (e.g. 1829-2134 m (6,000-7000 ft),
2134-2438 m (7001-8,000 ft), etc.). Lineage III worms had the greatest
abundance, outnumbering all of the other lineages combined, at all
elevations. The number of sites with lineage III worms was
approximately the same at all elevations from the 1829-2134 m (6,000-
7,000 ft) band up to the 3048-3353 m (10,000-11,000 ft) band (Nehring
2007, p. 10) indicating that the high-elevation cold-water streams do
not provide protection from lineage III worms.
One hundred and five conservation populations (88 percent) are
judged to have very limited risk from whirling disease or other
potential diseases because the pathogens are not known to exist in the
watershed or a barrier blocks upstream fish movement (Alves et al.
2007, p. 38). Six populations are at minimal risk because they are
greater than 10 km (6.2 mi) from the pathogen or they are protected by
a barrier, but the barrier may be at risk of failure (Alves et al.
2007, p. 38). Eight populations were identified as being at moderate
risk because whirling disease had been identified within 10 km of
occupied habitat (Alves et al. 2007, p. 38). In 2006, it was discovered
that whirling disease had infected brook trout and Rio Grande cutthroat
trout in Placer Creek, Colorado, a conservation population, and in 2007
it was chemically treated to remove infected fish and nonnative brook
trout.
In 2002, the Pecos, Cebolla, San Juan, Cimarron, Red, and Canones
rivers in New Mexico were listed as being infected with whirling
disease (67 FR 39943). By 2007, more than 80 streams and lakes had been
tested for the disease (Patten and Sloane 2007, pp. 10-13). North
Bonito Creek, Brazos River, and Los Pinos River were added to the list
of streams testing positive for whirling disease. Canones and Jacks
creeks, which had tested positive in 2000, tested negative in 2005, and
2003, respectively (Patten and Sloane 2007, pp. 10-13). Of the streams
listed, Rio Cebolla, Pecos River and Cimarron River are occupied by Rio
Grande cutthroat trout upstream above barriers.
NMDGF policies and regulations prohibit the stocking of any
whirling disease positive fish in the State of New Mexico (Patten and
Sloane 2007, p. 10). All private facilities must maintain a pathogen-
free certification. The Seven Springs Hatchery, which is used for Rio
Grande cutthroat trout broodstock, has tested negative on all occasions
since it was refurbished (Patten and Sloane 2007, p. 10). In Colorado
stocking of whirling disease positive fish in protected habitats, which
include native cutthroat trout waters, is prohibited (Japhet et al.
2007, p. 12). Colorado and New Mexico have web sites, brochures, and
information in their fishing regulations regarding whirling disease and
what anglers can do to prevent its spread. In addition, both States
have regulations regarding the stocking of fish by private landowners
that are designed to eliminate the importation of whirling disease
positive fish. It states clearly in the fishing regulations that it is
illegal to stock fish in public waters without prior permission from a
State agency.
Whirling disease remains a concern for Rio Grande cutthroat trout
populations. One Rio Grande cutthroat trout conservation population was
infected in Colorado, and restoration efforts were immediately
implemented to address the issue. Although widespread increases in M.
cerebralis have not been seen, additional infected sites have been
documented. Because of the limited level of infection currently,
whirling disease is not seen as a significant threat to populations
range-wide. However, climate change and warmer stream temperature may
facilitate the spread of whirling disease in the future (discussed in
the ``Disease'' section in Factor E below).
[[Page 27912]]
Predation
Brown trout are piscivores and are the most likely predator on Rio
Grande cutthroat trout. Additionally, brown trout have been found to
have a significant negative impact on the condition of coexisting Rio
Grande cutthroat trout through harassment (e.g., chasing) (Shemai 2004,
pp. 315-323; McHugh and Budy 2005, p. 2788). It is probable that larger
brown trout prey on young Rio Grande cutthroat trout and, unchecked,
brown trout can depress population levels. Warmer water temperatures in
the future may give brown trout a greater competitive advantage over
Rio Grande cutthroat trout (discussed in the ``Climate Change'' section
below). However, we have insufficient information at this time to
conclude that predation by brown trout is currently a significant
threat to Rio Grande cutthroat trout.
Summary of Factor C
One population of Rio Grande cutthroat trout has been infected with
whirling disease since our 2002 status review and eight conservation
populations are considered to be at moderate risk of infection.
Although whirling disease is currently limited in distribution and
effect, it has the potential to become a more widespread problem due to
warmer waters that could result from climate change (discussed in the
``Climate Change'' section below). We have insufficient information to
conclude that predation is a significant threat at this time.
Therefore, we conclude that the best scientific and commercial
information available to us indicates that, although the status of Rio
Grande cutthroat trout has not yet been affected by disease, Rio Grande
cutthroat trout is likely to be threatened by disease in the
foreseeable future.
D. The Inadequacy of Existing Regulatory Mechanisms
The NMDGF and the CDOW have authority and responsibility for the
management of Rio Grande cutthroat trout. Rio Grande cutthroat trout is
designated as a species of special concern by the State of Colorado and
of special management concern by the State of New Mexcio. The agencies'
capabilities include the regulation of fishing, law enforcement,
research, and conservation and educational activities relating to Rio
Grande cutthroat trout. Policies regarding the stocking of nonnative
fish (no nonnatives are stocked in Rio Grande cutthroat trout
populations), minimization of exposure to whirling disease and other
diseases, and broodstock management are in place in both States. In
2004, the ``Conservation Plan for Rio Grande Cutthroat trout in
Colorado'' was approved by the Director of CDOW. The goal of the plan
is to assure the long-term persistence of Rio Grande cutthroat trout
throughout its historic range by preserving genetic integrity, reducing
population fragmentation, and providing suitable habitat to support
self-sustaining populations (Japhet et al. 2007, p. ii). New Mexico
(2002) has an approved management plan currently being implemented that
will ``facilitate long range cooperative, interagency conservation of
Rio Grande cutthroat trout.''
Rio Grande cutthroat trout populations have been lost because of
stream drying (Japhet et al. 2007 pp. 42-44), and other trout
populations in the Southwest have been extirpated as the result of ash
flows following fire (Brown et al. 2001 p. 142). Imperiled fish
populations can be rescued from streams (Brooks 2004, pp. 1-15; Japhet
et al. 2007, p. 20). In the face of widespread drought or fire
(discussed in the ``Climate Change'' section below) it is expected that
many streams would be affected at one time, as seen in the 2002 drought
(Japhet et al. 2007, pp. 42-44; Patten et al. 2007, pp. 14-40). An
emergency rescue and evacuation plan is not in place for Rio Grande
cutthroat trout, nor do we anticipate that this strategy would be
effective in eliminating the threat of stream drying or post-fire ash
flows in the face of widespread drought.
In 2003, a range-wide conservation agreement was signed by CDOW,
NMDGF, USFS, the Service, BLM, NPS, and Jicarilla Apache Nation. The
purpose of the agreement is to facilitate cooperation and coordination
among State, Federal, and tribal agencies in the conservation of Rio
Grande cutthroat trout. The Conservation Team has met several times and
the ``Range-wide Status of Rio Grande Cutthroat Trout (Oncorhynchus
clarki virginalis): 2007'' is a product of the team's cooperative
effort.
Regulatory Mechanisms Involving Land Management
Numerous State and Federal laws and regulations help to minimize
adverse effects of land management activities on Rio Grande cutthroat
trout. Federal laws that protect Rio Grande cutthroat trout and their
habitats include the Clean Water Act (33 U.S.C. 1251 et seq.), Federal
Land Policy and Management Act (43 U.S.C. 1701 et seq.), National
Forest Management Act (16 U.S.C. 1600 et seq.), Wild and Scenic Rivers
Act (16 U.S.C. 1271 et seq.), Wilderness Act (16 U.S.C. 1131 et seq.),
and the National Environmental Policy Act (42 U.S.C. 4321 et seq.).
Approximately 59 percent of Rio Grande cutthroat trout habitat occurs
on lands managed by Federal agencies. The majority of those lands are
managed by the USFS. Rio Grande cutthroat trout occur over a large
geographic area within the Rio Grande, Santa Fe, and Carson National
Forests in Colorado and New Mexico. Rio Grande cutthroat trout is
designated as a sensitive species on all USFS lands.
The Regional Forester's Sensitive Species List policy is applied to
projects implemented under the 1982 National Forest Management Act
Planning Rule. However, in 2005, USFS implemented a new planning rule
(70 FR 1023, January 5, 2005), which directs land management plans to
be more strategic and less prescriptive. Under the new rule, land
management plans identify ecosystem-level desired conditions and
provide management objectives and guidelines to move toward the desired
conditions. The land management plans also will provide species-
specific direction for special status species when the broader
ecosystem-level desired conditions do not provide for their needs.
However, the United States District Court in Citizens for Better
Forestry et al. v. U.S. Department of Agriculture (N.D. Calif.)
enjoined the Forest Service from implementation and utilization of the
National Forest land management planning rule published on January 5,
2005 (70 FR 1023). Currently, the U.S. Department of Agriculture Office
of General Counsel is reviewing this matter and will provide legal
advice to USFS on how to proceed with forest planning. Therefore,
efforts specific to forest planning are postponed until further
direction is available (USFS 2008).
Threats to depletion of stream flow can be reduced by the U.S.
Forest Service utilizing its authorities, if any, to further secure
additional instream flows in Colorado. Rio Grande cutthroat trout
conservation populations are protected by State instream flow water
rights or USFS Reserve water rights along 620 km (385 mi) in 63 stream
segments (approximately 70 percent of occupied habitat) within the Rio
Grande basin in Colorado. Most of the remaining Rio Grande cutthroat
trout conservation populations that are not associated with instream
flow water rights are found on private property within the boundaries
of the old Spanish Land Grants where natural resource stewardship is
practiced. Regulatory controls of water quality in Colorado are
implemented by the
[[Page 27913]]
Colorado Water Quality Control Division and Commission. Water quality
standards are in place to protect the maintenance of aquatic life in
coldwater environments, and special resource restrictions are also
available to provide further site-specific protection to water quality
(Japhet et al. 2007, p. 18).
Summary of Factor D
The NMDGFG, CDOW and USFS are actively managing Rio Grande
cutthroat trout and its habitat. They also have authority for and are
undertaking fisheries management, research, educational and law
enforcement activities designed to improve the conservation status of
the species. There is a range-wide conservation agreement that also
involves the Service and other parties. Existing regulations,
authorities, and policies address current threats to the species that
are subject to regulatory control. However, climate change will have
potential impact throughout the range of this species. At this time it
is difficult to state how these effects will be addressed through
existing regulatory mechanisms.
E. Other Natural or Manmade Factors Affecting Its Continued Existence
Climate Change
In this section, we discuss the aspects of climate change that will
most likely affect the habitat of Rio Grande cutthroat trout. We begin
by presenting the evidence that indicates that climate change is
occurring globally. We then discuss literature related to climate
change that has been published for the Southwest and southern Rocky
Mountains that documents changes either that have already occurred or
that researchers predict will occur. Finally, we present data that have
been collected for streams occupied by Rio Grande cutthroat trout that
indicate that the effects of climate change could exacerbate the
threats discussed above.
The Intergovernmental Panel on Climate Change (IPCC) is a
scientific body set up by the World Meteorological Organization and the
United Nations Environment Program in 1988. It was established because
policymakers needed an objective source of information about the causes
of climate change, its potential environmental and socio-economic
consequences, and the adaptation and mitigation options to respond to
it. The Service considers the IPCC an impartial and legitimate source
of information on climate change. In 2007, the IPCC published its
Fourth Assessment Report, which is considered the most comprehensive
compendium of information on actual and projected global climate change
currently available.
Although the extent of warming likely to occur is not known with
certainty at this time, the IPCC (2007a, p. 5) has concluded that
warming of the climate is unequivocal and continued greenhouse gas
emissions at or above current rates would cause further warming (IPCC
2007a, p. 13). The IPCC also projects that there will very likely be an
increase in the frequency of hot extremes, heat waves, and heavy
precipitation (IPCC 2007a, p. 15). Warming in the Southwest is expected
to be greatest in the summer (IPCC 2007b, p. 887). Annual mean
precipitation is likely to decrease in the Southwest and the length of
snow season and snow depth are very likely to decrease (IPCC 2007b, p.
887). Most models project a widespread decrease in snow depth in the
Rocky Mountains and earlier snowmelt (IPCC 2007b, p. 891).
In consultation with leading scientists from the Southwest, the New
Mexico Office of the State Engineer prepared a report for the Governor
(State of New Mexico 2006) which made the following observations about
the impact of climate change in New Mexico:
(1) Warming trends in the American Southwest exceed global averages
by about percent (p. 5);
(2) Models suggest that even moderate increases in precipitation
would not offset the negative impacts to the water supply caused by
increased temperature (p. 5);
(3) Temperature increases in the Southwest are predicted to
continue to be greater than the global average (p. 5);
(4) There will be a delay in the arrival of snow and acceleration
of spring snow melt, leading to a rapid and earlier seasonal runoff (p.
6); and
(5) The intensity, frequency, and duration of drought may increase
(p. 7).
By the late 21st century, one simulation predicts no sustained snowpack
south of Santa Fe or in the Sangre de Cristo Mountains (State of New
Mexico 2006, p. 13). Snow pack would remain in far northern New Mexico
and southern Colorado but would be greatly reduced in mass, with a
decrease in water mass between one-third and one-half (State of New
Mexico 2006, p. 14).
Consistent with the outlook presented for New Mexico, Hoerling
(2007, p. 35) states that, relative to 1990-2005, simulations indicate
that a 25 percent decline in stream flow will occur from 2006-2030 and
a 45 percent decline will occur from 2035-2060 in the Southwest. Seager
et al. (2007, p. 1181) show that there is a broad consensus among
climate models that the Southwest will get drier in the 21st century
and that the transition to a more arid climate is already under way.
Only one of 19 models has a trend toward a wetter climate in the
Southwest (Seager et al. 2007, p. 1181). Stewart et al. (2004, p. 1152)
show that timing of spring streamflow in the western United States
during the last five decades has shifted so that the major peak now
arrives 1 to 4 weeks earlier, resulting in less flow in the spring and
summer. They conclude that almost everywhere in North America, a 10 to
50 percent decrease in spring-summer streamflow fractions will
accentuate the seasonal summer dry period with important consequences
for warm-season water supplies, ecosystems, and wildfire risks (Stewart
et al. 2004, p. 1154). An increase in average mean air temperature of
just over 1 [deg]C (2.5 [deg]F) in Arizona and just under 1 [deg]C (1.8
[deg]F) in New Mexico since 1976 has already been documented (Lenart
2007, p. 4). Udall (2007, p. 7) found that multiple independent data
sets confirm widespread warming in the West. Long-term studies (25 plus
years) of Mexican jays (Aphelocoma ultramarina) in Arizona and of
yellow-bellied marmots (Marmota flaviventris) in the Rocky Mountains
indicate changes in the timing of important life history events (e.g.,
breeding, emergence from hibernation) for both species related to
warmer temperatures (Parmesan and Galbraith 2004, pp. 18, 19).
As we will discuss below, climate change is predicted to have four
major effects on the cold water habitat occupied by Rio Grande
cutthroat trout: (1) Increased water temperature; (2) decreased stream
flow; (3) a change in the hydrograph (a graphical representation of the
distribution of water discharge or runoff over a period of time); and
(4) an increased occurrence of extreme events (fire, drought, and
floods).
Increased Water Temperature
Water temperature influences the survival of salmonids in all
stages of their life cycle. Alterations in the temperature regime from
natural background conditions negatively affect population viability,
when considered at the scale of the watershed or individual stream
(McCullough 1999, p. 160). Salmonids are classified as coldwater fish
with thermal preferences centered around 15 [deg]C (59 [deg]F) (Shuter
and Meisner 1992, p. 8). High temperatures suppress appetite and
growth, can influence behavioral interactions with other fish (Shrank
et al. 2003, p. 100), or can be lethal
[[Page 27914]]
(McCullough 1999, p. 156). Salmonids inhabiting warm stream segments
have higher probabilities of dying from stress (McCullough 1999, p.
156).
Eaton and Scheller (1996, p. 1111) state that the maximum
temperature tolerance for cutthroat trout is 23.3 [deg]C (74 [deg]F),
but Dunham et al. (2003b, p. 1042) state that Lahontan cutthroat trout
(Oncorhynchus clarki henshawi) show signs of stress (decreased growth
and appetite and increased mortality) when water temperature exceeds 22
[deg]C (71.6 [deg]F) for even a short time (less than 1 day). For
Bonneville cutthroat trout, the 7-day upper incipient lethal
temperature (temperature lethal to 50 percent of the fish) was 24.2
[deg]C (75.6 [deg]F) under constant thermal conditions (Johnstone and
Rahel 2003, p. 96). However, when the temperature was cycled daily
between 16-26 [deg]C (60.8-78.8 [deg]F) for 7 days, similar to what the
trout would experience in high mountain streams, all trout survived
(Johnstone and Rahel 2003, p. 97). Dickerson and Vineyard (1999, pp.
519, 520) found a similar result (cycling between 20 and 26 [deg]C (68
and 78.8 [deg]F)) for Lahontan cutthroat trout. Although trout may
survive cyclic exposures to high temperatures, growth is slowed or
stopped due to the high metabolic costs and reduced food intake
(Dickerson and Vineyard 1999, p. 519; Johnstone and Rahel 2003, p. 98).
Although temperature preferences of Rio Grande cutthroat trout have
not been researched specifically, their optimum growth temperature
(appetite is high and maintenance requirements low) is most likely in
the range of 13-15 [deg]C (55.4-59 [deg]F), similar to other cutthroat
trout (Meeuwig et al. 2004, p. 213; Bear et al. 2007, p. 1118) and
their upper incipient lethal limit is most likely near 23-24 [deg]C
(73.4-75.2 [deg]F), as has been found for other subspecies of cutthroat
trout (Wagner et al. 2001, p. 434; Johnstone and Rahel 2003, p. 97).
Upper incipient lethal limit (temperature at which 50 percent of the
fish can survive for 7 days) for rainbow trout ranges from 24-26 [deg]C
(75.2-78.8 [deg]F), for brown trout 23-26 [deg]C (73.4-78.8 [deg]F),
and for brook trout 24-25 [deg]C (75.2-77 [deg]F) (McCullough 1999, pp.
47, 48), which means these nonnative trout are better able to tolerate
higher water temperatures than cutthroat trout.
The IPCC states that of all ecosystems, freshwater ecosystems will
have the highest proportion of species threatened with extinction due
to climate change (Kundzewicz et al. 2007, p. 192). Species with narrow
temperature tolerances will likely experience the greatest effects from
climate change, and it is anticipated that populations located at the
margins of species' hydrologic and geographic distributions will be
affected first (Meisner 1990a, p. 282). Climate change has already had
or is predicted to have negative consequences on coldwater fisheries
globally (Nakano et al. 1996, p. 711; Hari et al. 2006, p. 24), across
North America (Meisner 1990a, pp. 287, 290; Regier and Meisner 1990, p.
11; Carpenter et al. 1992, p. 124; Eaton and Scheller 1996, p. 1111;
O'Neal 2002, p. 3; Poff et al. 2002, p. iv; Chu et al. 2005, p. 303;
Preston 2006, pp. 106, 107, 110, 111, 115; Reiman et al. 2007, pp.
1553, 1558), and in the Southwest and Rocky Mountains specifically
(Keleher and Rahel 1996, p. 1; Rahel et al. 1996, pp. 1116, 1122;
O'Neal 2002, pp. 43, 44; Preston 2006, pp. 101, 102, 113) through
increases in ground and surface water temperature.
The magnitude of habitat loss due to increased water temperature
depends on the climate change model used, the model used to predict the
air temperature/water temperature relationship, and the timeframe.
Keleher and Rahel (1996, p. 4) found that the distribution of salmonids
in Wyoming streams was limited to areas where mean July air temperature
did not exceed 22 [deg]C (71.6 [deg]F). They projected that for
temperature increases of 1, 2, 3, 4, or 5 [deg]C, there would be a
corresponding loss of area suitable for salmonids of 16.2, 29.1, 38.5,
53.3, and 68.0 percent, respectively (Keleher and Rahel 1996, p. 4).
Rahel et al. (1996) used three approaches to examine potential salmonid
habitat loss due to warming in the North Platte river drainage of the
Rocky Mountains. They found that there was a loss of 9 to 76 percent of
coldwater habitat based on air temperature increases of 1 to 5 [deg]C
(Rahel et al. 1996, p. 1120). Other studies have predicted losses of
18-92 percent of suitable natal bull trout (Salvelinus confluentus)
habitat (Rieman et al. 2007, p. 1558), and Preston (2006, p. 92), in a
re-analysis of other studies, found a 20, 35, and 50 percent loss of
coldwater habitat from the Rocky Mountains in 2025, 2050, and 2100,
respectively.
In these studies, habitat loss occurs in the lower elevation stream
reaches (or lower latitude streams) due to increased temperatures. As a
result, salmonid populations will be restricted to increasingly higher
elevations or to more northern latitudes (Meisner et al. 1988, p. 6;
Regier and Meisner 1990, p. 11; Keleher and Rahel 1996, p. 2; Nakano et
al. 1996, pp. 716, 717; Rahel et al. 1996, p. 1122; Poff et al. 2002,
p. 7; Rieman et al. 2007, p. 1558). Consequently, coldwater species
occupying the southern distributions of their range are seen as more
susceptible to extirpation as a consequence of global climate change
(Poff et al. 2002, p. 8; Rieman et al. 2007, pp. 1552, 1553). Rio
Grande cutthroat trout are the southernmost subspecies of cutthroat
trout (Behnke 2002, p. 143).
Rio Grande cutthroat trout primarily occupy high-elevation
headwater tributaries. Dispersal to new habitats is unlikely because
they currently occupy the uppermost available habitat. Warming of lower
elevation stream segments may limit restoration opportunities in the
future and provide a competitive advantage to brown, rainbow, and brook
trout in locations where these nonnatives occur with Rio Grande
cutthroat trout (De Staso and Rahel 1994, pp. 293, 294; Dunham et al.
2002, p. 380; Paroz 2005, p. vi; Bear et al. 2007, p. 1118; Shemai et
al. 2007, p. 322).
The Santa Fe and Carson National Forests have monitored stream
temperature data using thermographs (instruments that record
temperature at designated intervals, e.g., once every 4 hours) (Eddy
2005, Martinez 2007). From 2001-2003, 47 thermograph stations were used
to monitor 21 streams on the Santa Fe National Forest, representing 385
km (239 mi) of stream (Eddy 2005, p. 5). Seven of the 21 streams are
currently occupied by Rio Grande cutthroat trout conservation
populations; all 21 are believed to be historical habitat. Temperature
data collected were compared with New Mexico Environment Department
(NMED) standards for high quality coldwater fisheries and with Santa Fe
National Forest standards, which are slightly more stringent than NMED
but are more in line with standards for coldwater fisheries in the
western States (Table 3) (Eddy 2005, p. 4). ``Properly functioning''
indicates that the water temperature of the stream is within the
optimal range for feeding, physiology, and behavior for coldwater fish.
``At risk'' indicates that the water temperature is slightly warmer
than optimal, and ``not properly functioning'' indicates that the water
temperature is too warm to support a healthy coldwater fishery.
[[Page 27915]]
Table 3.--Santa Fe National Forest and NMED
[Water quality temperature standards for high quality coldwater fisheries]
----------------------------------------------------------------------------------------------------------------
Water temperature standards Properly functioning At risk Not properly functioning
----------------------------------------------------------------------------------------------------------------
Santa Fe National Forest 7- <=64 [deg]F (<=17.8 64 to 70 [deg]F........... >70 [deg]F (>21.1 [deg]C).
Day Average Maximum. [deg]C). (17.8-21.1 [deg]C)........
NMED 3-Day Average Maximum.. <68 [deg]F (<20 [deg]C)... 68 to <73.4 [deg]F........ >=73.4 [deg]F (23 [deg]C).
(20 to <23 [deg]C)........
----------------------------------------------------------------------------------------------------------------
Using the Santa Fe National Forest standards, stream segments
represented by 12 thermograph stations were properly functioning (67.3
km (41.8 mi)), stream segments represented by 20 stations were at risk
(162.1 km (100.7 mi)), and stream segments represented by 15 stations
were not properly functioning (154.7 km (96.1 mi)) (Eddy 2005, p. 5).
Using NMED standards, stream segments represented by 23 stations (172.7
km (107.3 mi)) were properly functioning, stream segments represented
by 12 stations (82.2 km (51.1 mi)) were at risk, and stream segments
represented by 12 stations (129.1 km (80.2 mi)) were not properly
functioning (Eddy 2005, p. 5). Only nine streams were properly
functioning for their entire length, using both standards. Of these,
only one is occupied by a Rio Grande cutthroat trout conservation
population (Cave Creek) (Eddy 2005, p. 5). The Pecos River and Rio de
las Vacas are properly functioning in occupied Rio Grande cutthroat
trout habitat but have at risk (Pecos River) or not properly
functioning sections (Rio de las Vacas) below occupied habitat (Eddy
2005, pp. 34, 35, 92). Canones, Polvadera, and Rio Cebolla were the
other streams monitored that have conservation populations of Rio
Grande cutthroat trout. These streams were identified as at risk or not
properly functioning (Rio Cebolla) in occupied habitat (Eddy 2005, pp.
9, 19, 26).
Monitoring on the Carson National Forest indicated that Comanche
Creek had several periods in which temperature standards were exceeded
(Martinez 2007, pp. 3-22). Eight sites on Comanche Creek were monitored
in 1998, 1999, and 2004. Temperatures were highest in 1998 and 1999,
years of lower runoff. Temperatures in 1998 were very high, with 5 of
the 8 sites recording temperatures from 26.6-29.5 [deg]C (80-85 [deg]F)
(Martinez 2007, pp. 3-22). At the remaining three sites, temperatures
reached 26.4 [deg]C (79.5 [deg]F). Thermographs went in on June 23 each
year, and in 1998, maximum temperatures ranged from 22.9-24 [deg]C
(73.2-76 [deg]F) at all eight sites on the first day the recorders were
deployed, indicating that there were probably several days of warm
temperatures that occurred before monitoring began (Martinez 2007, pp.
3-22). In total, of 14 streams occupied by Rio Grande cutthroat trout
and monitored by thermographs on the Santa Fe and Carson National
Forests, 8 streams were either at risk or not properly functioning
because of high water temperature (NMED 2007, pp. 15-331; Eddy 2005,
pp. 8-116; Martinez 2007, pp. 3-22). An additional conservation
population in Colorado was also identified at risk from high water
temperatures by Pritchard and Cowley (2006, p. 39). Because only a
fraction of the streams occupied by Rio Grande cutthroat trout have
been monitored, there are likely more that are at risk.
The thermograph data collected on the Santa Fe and Carson National
Forests indicate that stream temperatures in several streams are
already at risk or are considered ``not properly functioning'' for
trout. Because air temperature and consequently water temperature are
expected to increase with climate change, we would anticipate that more
streams that are currently not properly functioning will become
unsuitable for Rio Grande cutthroat trout, those currently at risk will
enter the not properly functioning category, and more streams will fall
into the at risk category for temperature. As a consequence, suitable
habitat will decrease and fragmentation will increase.
In contrast to the potential negative impacts of water temperature
increase on Rio Grande cutthroat trout, there could also be a potential
benefit. Cold summer water temperatures (mean July temperature of less
than 7.8 [deg]C (46 [deg]F)) have been found as a limiting factor to
recruitment of cutthroat trout in high-elevation streams (Harig and
Fausch 2002, p. 545; Coleman and Fausch 2007, pp. 1238-1240). Coleman
and Fausch (2007, p. 1240) found that cold summer water temperatures in
Colorado streams likely limited recruitment of cutthroat trout because
of reduced survival of age-0 fish (fish less than 1 year old). Harig
and Fausch (2002, p. 538) recorded summer water temperatures in 5
streams in New Mexico and 11 streams in Colorado from 1996 to 1999
(Harig and Fausch 2002, p. 540). None of the streams in New Mexico had
July water temperatures below 7.8 [deg]C (46 [deg]F) (lowest July
average was in the Pecos River, 9.2 [deg]C (48.6 [deg]F)). Three of
four streams in Colorado that no longer had translocated fish present
had summer averages below 7.8 [deg]C (46 [deg]F) (Harig and Fausch
2002, pp. 538, 539). The remaining 8 streams in Colorado had summer
averages >=8.3 [deg]C (46.9 [deg]F), indicating that cold summer water
temperatures were most likely not limiting for these Rio Grande
cutthroat trout populations (Harig and Fausch 2002, pp. 538, 539). Two
of the four streams (Little Medano and Unknown Creek), which no longer
had transplanted fish at the time of Harig and Fausch's research (1996-
1998), dried in 2002 (Alves et al. 2007, pp. 43, 44), raising the
possibility that insufficient refugial habitat may have been limiting,
not low summer water temperatures.
Cold summer water temperatures have been identified as limiting in
one stream: Deep Canyon, Colorado (Pritchard and Cowley 2006, p. 42).
However, Alves et al. (2007 database) indicate that Deep Canyon has
temperatures from 8 to 16 [deg]C (46.4 to 60.8 [deg]F) during spawning
and incubation periods. Of the 14 Rio Grande cutthroat trout streams
monitored with thermographs on the Santa Fe and Carson National
Forests, two (Pecos and Mora rivers) were found to have July
temperatures less than 7.8 [deg]C (46 [deg]F) (data summarized from
Eddy 2005, Martinez 2007). The result for the Pecos River contrasts
with the data Harig and Fausch (2002, p. 540) collected (9.2 [deg]C
(48.6 [deg]F)) and likely reflects a difference in thermograph
placement or year (e.g., temperature variability, amount of runoff).
In summary, we find that data collected thus far indicate that warm
water temperatures have already reached the likely limits of
suitability in some Rio Grande cutthroat trout streams and several
others are at risk. Water temperatures are expected to increase in the
future, affecting more streams and making lower elevation reaches
either
[[Page 27916]]
marginal or unsuitable. This is particularly true for populations that
are located in New Mexico and are at the southernmost extent of the
range but could also be true for smaller streams in Colorado. Although
cold water temperatures are limiting to some high-elevation salmonid
populations, cold water limitation has not been convincingly
demonstrated for any Rio Grande cutthroat trout population. Therefore,
we view the negative impact of stream warming to outweigh any benefit
that may occur from increased water temperature.
The studies cited above that forecast coldwater habitat loss,
calculate the loss of habitat based on increases in temperature alone,
assuming temperatures will rise above the thermal tolerance limits of
coldwater species, thereby limiting the amount of suitable habitat
available. The ancillary effects of increased temperature, such as
increased habitat fragmentation (Rahel et al. 1996, pp. 1121, 1122;
Rieman et al. 2007, pp. 1553, 1560, 1562), changes in invertebrate prey
base (both species composition and availability) (Ries and Perry 1995,
p. 204; O'Neal 2002, p. 4; IPCC 2002, p. 17; Harper and Peckarsky 2006,
p. 618; Bradshaw and Holazpel 2008, p. 157), effects on spawning (Jager
et al. 1999, p. 236), increased competitive interactions with nonnative
trout (Meisner 1990b, p. 1068; De Staso and Rahel 1994, pp. 289, 294;
O'Neal 2002, p. 33; Chu et al. 2005, p. 307; Sloat et al. 2005, p.
235), additional invasive species (IPCC 2002, p. 32), increased
susceptibility to disease (Hari et al. 2006, p. 24), and effects on
water quality (e.g., dissolved oxygen, nutrients, pH) (Meisner et al.
1988, p. 7), are not considered in calculating the potential habitat
loss.
Of these factors, increased fragmentation, increased effects from
nonnative fish, and increased disease risk are considered of particular
importance to Rio Grande cutthroat trout and are discussed in more
detail.
Fragmentation. Climate change is predicted to increase
fragmentation of coldwater fish habitat (Nakano et al. 1996, p. 719;
Rahel et al. 1996, p. 1122; Rieman et al. 2007, p. 1553). Currently,
112 of 120 (93 percent) conservation populations of Rio Grande
cutthroat trout exist as fragments, with no well-connected populations
(Alves et al. 2007, p. 29). Only one population has a moderate degree
of connectivity (Comanche Creek) (2007 database). As noted above,
Comanche Creek currently has very high water temperatures (Martinez
2007, pp. 3-22), and several of the small tributaries of upper Comanche
Creek dried in 2006 (Patten et al. 2007, p. 76). Consequently, the one
moderately well-connected population may already be at risk. Seven Rio
Grande cutthroat trout conservation populations are considered weakly
networked (occupied habitat consists of 2-3 connected streams, possible
infrequent straying of adults may occur) (Alves et al. 2007, p. 77). Of
these seven, six have connecting stream segments less than 5 feet in
width (2007 database), and are therefore considered at risk from
drying. Consequently, fragmentation of these weakly networked systems
appears reasonably likely in the foreseeable future.
Nonnative Fish Interactions. Water temperature is a determining
factor in the distribution of salmonids (Rahel and Hubert 1991, p. 326;
Schrank et al. 2003, p. 100; Sloat et al. 2005, p. 225). Additionally,
temperature regime is a key determinant of the outcome of competitive
interactions in a fish community (MuCullough 1999, p. 156). Fish living
within their optimum temperature range have improved performance
relative to other species not within their optimum range (MuCullough
1999, p. 156). There is evidence that the reason cutthroat trout occupy
headwater streams and rainbow, brook, and brown trout occupy downstream
reaches is because of the influence of temperature on competitive
abilities (Dunham et al. 2002, p. 380). DeStaso and Rahel (1994, pp.
293, 294) looked at competition between Colorado River cutthroat trout
(Oncorhynchus clarki pleuriticus) and brook trout. They found that at
warmer water temperatures (20 [deg]C (68 [deg]F)) brook trout was
dominant, as evidenced by a higher level of interspecific aggression,
more time spent at the optimal feeding position, and greater food
consumption (DeStaso and Rahel 1994, pp. 293, 294). Brook trout also
tolerated higher temperatures (DeStaso and Rahel 1994, p. 294).
As mentioned earlier, when brook trout co-occur with cutthroat
trout, species interactions act to suppress cutthroat trout populations
(Dunham et al. 2002, p. 378; Young and Guenther-Gloss 2004, p. 193;
Peterson et al. 2004, pp. 765-769). Because brook trout tolerate higher
temperatures, warmer stream temperatures would provide a competitive
advantage to brook trout over Rio Grande cutthroat trout, exacerbating
the problems that already exist for Rio Grande cutthroat trout
populations.
In New Mexico, brown trout is the most common nonnative trout
present in Rio Grande cutthroat trout conservation populations
(summarized from 2007 database). Jager et al. (1999, p. 232) modeled
the effects of an increase of 2 [deg]C air temperature on brown trout
distribution in the Sierra Nevada, California. They found that brown
trout numbers would increase in upstream cooler reaches, and decrease
downstream through starvation of juvenile and adult fish (Jager et al.
1999, p. 235). This is consistent with observations in Switzerland. In
Switzerland in 1987, after a long period of essentially stable river
water temperatures, water temperatures took an abrupt and significant
increase to a higher mean level, which was attributed to a
corresponding increase in air temperature (Hari et al. 2006, pp. 10,
21). Suitable habitat for brown trout, a trout species native to the
area, moved upstream, and downstream portions became unsuitable (Hari
et al. 2006, pp. 10, 21).
McHugh and Budy (2005, p. 2791) hypothesized that cold incubation
temperatures might explain why brown trout did not form self-sustaining
populations at high elevations in Logan River, Utah, where upstream
water temperatures were not too cold for adult brown trout. Because
brown trout have a higher optimal growth temperature (between 13-18
[deg]C) than cutthroat trout (12-13 [deg]C), and because cold
incubation temperatures may currently be limiting brown trout range
expansion upstream, it is anticipated that warmer water temperatures
will make additional upstream habitat suitable for brown trout,
reducing the area where Rio Grande cutthroat trout are now dominant.
When cutthroat trout co-occur with rainbow trout, cutthroat trout
typically occupy the upper colder reaches and rainbow trout occupy the
lower, warmer stream reaches (Sloat et al. 2005, p. 235; Robinson 2007,
p. 80). As identified by Alves et al. (2007, p. 35), rainbow trout
occupy the same stream reaches as four conservation populations of Rio
Grande cutthroat trout. Rainbow trout have a higher thermal tolerance
than do cutthroat trout (Bear et al. 2007, pp. 1115, 1116). Because
rainbow trout are able to tolerate higher temperatures than Rio Grande
cutthroat trout, we expect that warming stream temperatures will give
rainbow trout a competitive advantage over Rio Grande cutthroat trout.
Monitoring and maintenance of barriers will continue to be essential,
to prevent hybridization and competition.
White sucker is native to the middle elevations of the Pecos and
Canadian river drainages in New Mexico, but it has been introduced
widely throughout the State and is sympatric with at least two
populations of Rio Grande cutthroat trout (Sublette et al. 1990, p.
199; 2007
[[Page 27917]]
database). White sucker has a preferred water temperature of 22.4-27.1
[deg]C (72.3-80.8 [deg]F) (Sublette et al. 1990, p. 198). Sublette et
al. (1990, p.199) note that white sucker is highly fecund (able to
reproduce) and often dominates a body of water. Comanche Creek
(elevation approximately 2900 m (9500 ft)) has an abundant white sucker
population, most likely due to the warm water temperatures discussed
above. In 2007, over 20,000 white sucker were removed from Comanche
Creek during a Rio Grande cutthroat trout restoration project (Patten
2007). Before the restoration, fish biomass was dominated by white
sucker, and an inverse relationship was found between Rio Grande
cutthroat trout density and white sucker density (Patten et al. 2007,
pp. 17, 18). Because both white sucker and Rio Grande cutthroat trout
feed on aquatic insects, there is the potential for high numbers of
white sucker to negatively impact food availability for Rio Grande
cutthroat trout. We would anticipate the warmer stream temperatures
would lead to more stream habitat becoming suitable for white sucker
with potential negative impacts on Rio Grande cutthroat trout
populations.
Disease. As mentioned earlier (see the ``Disease and Predation''
section in Factor C above) it had been thought that Rio Grande
cutthroat trout were provided some level of protection against whirling
disease because tubificid worms are most abundant in warm, degraded
habitats and Rio Grande cutthroat trout occur in high-elevation,
coldwater streams (67 FR 39943). However, Nehring (2007, p. 10) found
equal abundance of lineage III tubificid worms in elevations from 1,829
m (6,000 ft) to 3,657 m (12,000 ft). Thus, it is clear that elevation
does not provide protection from exposure to the disease.
El-Matubouli et al. (1999) found that temperatures from 10-15
[deg]C (50-59 [deg]F) were optimum for development and maturation of
the parasite inside the tubificid worm. Blazer et al. (2003, p. 24)
found that the greatest production of TAMs occurred at temperatures
from 13-17 [deg]C (55.4-62.6 [deg]F). Although the effect of
temperature on survival of the tubificid worms was not statistically
detectable, DuBey et al. (2005, p. 341) found that survival was
consistently higher at 17 [deg]C (62.6 [deg]F) than at 5 [deg]C (41
[deg]F). Schisler et al. (2000, p. 862) found that multiple stressors
on rainbow trout, especially the combination of M. cerebralis infection
and temperature, increased mortality drastically. At 12.5 [deg]C (54.5
[deg]F) mean mortality of rainbow trout exposed to M. cerebralis was
41.7 percent. Mean mortality of rainbow trout exposed to M. cerebralis
and held at a temperature of 17 [deg]C (62.6 [deg]F) was 60 percent
(Schisler 2000, p. 861). Water temperature often exceeds 17 [deg]C
(62.6 [deg]F) in July and August in Rio Grande cutthroat trout streams
that have been monitored (Eddy 2005, Martinez 2007).
Thompson et al. (1999, p. 318) found that as water temperature
increased from May to July, rainbow and cutthroat trout infected with
M. cerebralis suffered high rates of mortality even though they had
survived well in the winter. In a field study of the effects of water
temperature, discharge, substrate size, nutrient concentration, primary
productivity, and relative abundance of T. tubifix, de la Hoz Franco
and Budy (2004, p. 1183) found that prevalence of M. cerebralis in
trout increased with water temperature. Across sites where cutthroat
trout were present, the lowest prevalence of infection occurred in the
headwaters where average daily water temperature was 9.2 [deg]C (48.6
[deg]F), whereas the highest levels of infection occurred at a low
elevation site where the temperature was the highest (>12 [deg]C (53.6
[deg]F)) (de la Hoz Franco and Budy 2004, p. 1186).
While water temperature in some streams may warm to the point (>20
[deg]C (68 [deg]F)) of inhibiting the production of TAMs (Blazer et al.
2003, p. 24), it is anticipated that the overall increases in water
temperature will be favorable for T. tubifix and TAM production. From
these studies we conclude that elevation does not provide protection to
Rio Grande cutthroat trout populations and that increasing water
temperature would increase the production of TAMs and the survival of
tubificid worms (up to about 20 [deg]C (68 [deg]F)), and increased
water temperature would increase mortality of infected Rio Grande
cutthroat trout.
In summary, stream warming will most likely decrease the amount of
suitable habitat available for Rio Grande cutthroat trout. Warmer
stream temperatures may in the foreseeable future make currently
occupied reaches of stream more stressful or unsuitable. Suitable
habitat is likely to be reduced, primarily at the downstream end of
stream reaches and in small tributaries, leading to increased
fragmentation, shorter occupied segments, and increased risk of
extirpation. Warmer water temperatures will allow nonnative fishes to
expand their range and give them a competitive advantage over Rio
Grande cutthroat trout. Stress from warm water temperatures increases
susceptibility to and mortality from disease. Although whirling disease
positive sites are currently still limited within the range of Rio
Grande cutthroat trout, managers will need to continue to monitor the
disease closely. Increased water temperatures would increase the threat
posed by whirling disease.
Decreased Stream Flow
Current models suggest a decrease in precipitation in the Southwest
(Seager et al. 2007, p. 1181; Kundzewicz et al. 2007, p. 183), which
would lead to reduced stream flows and a reduced amount of habitat for
Rio Grande cutthroat trout. Stream flow is also predicted to decrease
in the Southwest even if precipitation were to increase moderately
(Nash and Gleick 1993, p. ix; State of New Mexico 2005, p. 6; Hoerling
2007, p. 35). Winter and spring warming causes an increased fraction of
precipitation to fall as rain, resulting in a reduced snow pack, an
earlier snowmelt, and decreased summer runoff (Christensen et al. 2004,
p. 4; Stewart et al. 2005, p. 1137; Regonda et al. 2005, p. 373).
Earlier snowmelt and warmer air temperatures lead to a longer dry
season, which affects stream flow. Warmer air temperatures lead to
increased evaporation, increased evapo-transpiration, and decreased
soil moisture. These three factors would lead to decreased stream flow
even if precipitation increased moderately.
The effect of decreased stream flow is that streams become smaller,
thereby reducing the amount of habitat available for aquatic species
(Lake 2000, p. 577). A smaller stream is affected more by air
temperature than a larger one, exacerbating the effects of warm (and
cold) air temperature (Smith and Lavis 1975, p. 229). Small headwater
streams, such as those occupied by Rio Grande cutthroat trout, and
intermittent streams may dry completely. Seventy-one percent of Rio
Grande cutthroat trout streams are less than 8 km (5 mi) in length
(Alves et al. 2007, p. 26). Because stream length is one indicator of
population viability (Harig et al. 2000, p. 997; Hilderbrand and
Kershner 2000, p. 515; Young et al. 2005, p. 2405; Cowley 2007 10.1002/
aqc.845), further shortening of Rio Grande cutthroat trout streams due
to drying is expected to have a negative impact on populations.
In fact, fourteen Rio Grande cutthroat trout streams with
conservation populations became intermittent, and had populations
negatively impacted or lost because of the 2002 drought (Japhet et al.
2007, pp. 42-44; Patten et al. 2007, pp. 14, 31, 32, 34, 39, 76). The
number of streams impacted was most likely higher, because managers
only survey a fraction of the 120 conservation populations in any given
year. Approximately 27 conservation
[[Page 27918]]
populations are in streams that are 1.5 m (5 ft) or less in width
throughout their entire length (2007 database). An additional 29 stream
segments that are tributaries to the conservation populations are also
less than 1.5 m (5 ft) in width (2007 database), which indicates that
fragmentation of existing connected populations could increase. We
recognize that not all streams less than 1.5 m (5 ft) wide have an
equal probability of drying. Some are likely spring fed or are narrow
and deep, thus decreasing the likelihood of drying. However, because of
the high number of Rio Grande cutthroat trout streams less than 8 km (5
mi) in length (71 percent of conservation populations) and less than
1.5 m (5 ft) wide, the risk of drying is considered high.
Insight into the effects that climate change may have on headwater
streams is provided by research done at the Experimental Lakes Area in
northwestern Ontario (Schindler et al. 1996). The experimental area was
set up in 1968, and precipitation, evaporation, air temperature, wind
velocity, and other meteorological and hydrological parameters were
monitored continuously throughout the 1970 to 1990 study period
(Schindler et al. 1996, p. 1005). During this period, the area
experienced gradual air temperature warming (1.6 [deg]C (2.9 [deg]F))
and decreased precipitation (as measured by a decline of over 50
percent in annual runoff) (Schindler et al. 1996, p. 1004). Whether
these changes can be attributed to climate change or local variation is
unknown, but they are consistent with changes that are predicted under
global climate change scenarios. In the early 1970s, two streams in the
area were perennial and one stream was dry for less than 10 days per
year. By the late 1980s all three streams were dry for 120-160 days
during the summer (Schindler et al. 1996, p. 1006). Because northern
latitude ecosystems mimic higher elevation systems in southern
latitudes, the effects seen on these streams likely represent what may
happen at high-elevation streams in New Mexico and Colorado, within the
range of Rio Grande cutthroat trout.
In summary, stream drying has already had a negative impact on
several Rio Grande cutthroat trout populations; 71 percent of Rio
Grande cutthroat trout conservation populations are in stream fragments
8 km (5 mi) or less in length, and many of the populations are in
streams less than 1.5 m (5 ft) wide. Further, the increased risk of
stream drying as a result of climate change, leading to shorter stream
segments and increased fragmentation, is seen as high. A rangewide
emergency rescue and evacuation plan does not exist for Rio Grande
cutthroat trout and would likely not be effective. If widespread
drought were to occur, affecting many streams at the same time, it is
unclear if sufficient facilities or donor streams exist to accept the
rescued fish, or if the effort would take place according to a
carefully conceived, well-organized plan.
Change in Hydrograph
Changes in air temperature and precipitation will likely lead to
changes in the magnitude, frequency, timing, and duration of runoff
(Poff et al. 2002, p. 4). Stewart et al. (2004, p. 1152) show that
spring streamflow during the last five decades has shifted so that the
major peak now arrives 1 to 4 weeks earlier, resulting in declining
fractions of flow in the spring and summer. The life history of
salmonids is closely tied to the flow regime, runoff in particular
(Fausch et al. 2001, p. 1440). A change in timing or magnitude of
floods can scour the streambed, destroy eggs, or displace recently
emerged fry downstream (Erman et al. 1988, p. 2199; Montgomery et al.
1999, p. 378; Fausch et al. 2001, p. 1440). The environmental cues for
spawning of Rio Grande cutthroat trout are not known with certainty,
but they are most likely tied to increasing water temperature,
increasing day length, and possibly flow, as it has been noted that
they spawn when runoff from snowmelt has peaked and is beginning to
decrease (Behnke 2002, p. 141; Pritchard and Cowley 2006, p. 25).
Consequently, a change in the timing of runoff from spring to winter
could disrupt spawning cues because peak flow would occur when the days
are still short in length and water temperatures cold.
Increased winter temperatures cause more precipitation to fall as
rain instead of snow (Regonda et al. 2005, p. 373). Snow covering small
streams provides valuable insulation that protects aquatic life
(Needham and Jones 1959, p. 470; Gard 1963, p. 197). Gard (1963, p.
196) measured temperatures above, within, and below the snow at Sagehen
Creek, California, a small Sierra Nevada mountain stream. He found that
although there was a 35.4 [deg]C (63.8 [deg]F) diurnal air temperature
variation, within the snow the temperature variation was only 1.3
[deg]C (2.3 [deg]F) and the water temperature in the stream below
varied by only 0.3 [deg]C (0.55 [deg]F). Stream freezing, which is more
likely absent insulating snow cover, has been suggested as the cause of
the extirpation of one Rio Grande cutthroat trout population (Ferrell
2006, p. 11). Anchor ice (ice frozen on the stream bed) and frazil ice
(ice crystal suspended in the water) can also have negative impacts on
trout (Needham and Jones 1959, p. 465). High-elevation streams are
rarely visited in winter; consequently, it is difficult to document the
extent to which freezing may impact populations. However, the
combination of reduced stream flow and reduced snow pack could lead to
an increased probability of stream freezing in small headwater Rio
Grande cutthroat trout streams.
Earlier snowmelt, which leads to less flow in the spring and
summer, could either benefit Rio Grande cutthroat trout or be
detrimental. The benefit could come because the young-of-year would
have a longer growing season before winter. However, as discussed
above, a longer season of lower flows would lead to increased stream
temperatures and increased probability of intermittency and drying.
In summary, it is difficult to project how changes in the
hydrograph as a result of climate change will affect Rio Grande
cutthroat trout populations. If growing season is increased, water
temperatures remain suitable, and the stream does not dry, a beneficial
effect could occur. If spawning cues are disrupted or egg and fry
success is reduced because of winter floods or unseasonal extreme
floods, a negative impact would occur. In addition, stream freezing may
reduce suitable over-winter habitat or reduce population size in
susceptible streams.
Extreme Events
An increase in extreme events such as drought, fires, and floods is
predicted to occur because of climate change (IPCC 2007a, p. 15). It is
anticipated that an increase in extreme events will most likely affect
populations living at the edge of their physiological tolerances. The
predicted increases in extreme temperature and precipitation events may
lead to dramatic changes in the distribution of species or to their
extirpation or extinction (Parmesan and Matthews 2006, p. 344).
Drought. The relatively short-term drought of the early 2000s had a
negative impact on or extirpated 14 Rio Grande cutthroat trout
populations in Colorado and New Mexico (Japhet et al. 2007, pp. 42-44;
Patten et al. 2007, pp. 14-40). A fifteenth population is thought to
have been extirpated in 2006 by complete freezing caused by low flow in
the winter (Ferrell 2006, p. 11). As discussed above, in the
``Decreased Stream Flow'' section, it is anticipated that a prolonged,
intense drought would affect many Rio Grande cutthroat trout
populations, in particular those less
[[Page 27919]]
than 1.5 m (5 ft) wide and less than 8 km (5 mi) long because of their
small size.
Most Rio Grande cutthroat trout populations are currently protected
from downstream populations of nonnative trout by barriers. Downstream
reaches are larger streams that historically could have provided
refugia for populations threatened by stream drying. If Rio Grande
cutthroat trout disperse downstream now, they are lost from their
conservation population once they pass over the barrier because they
will not be able to pass back over the barrier moving the upstream
direction. In the future, downstream water temperatures may be too warm
to be suitable for Rio Grande cutthroat trout. In addition to stream
drying, there is a clear association between severe droughts and large
fires in the Southwest (Swetnam and Baisan 1994, pp. 11, 24, 28), as
discussed below.
Fire. Since the mid-1980s, wildfire frequency in western forests
has nearly quadrupled compared to the average of the period 1970-1986.
The total area burned is more than six and a half times the previous
level (Westerling et al. 2006, p. 941). In addition, the average length
of the fire season during 1987-2003 was 78 days longer compared to
1970-1986 and the average time between fire discovery and control
increased from 7.5 days to 37.1 days for the same timeframes
(Westerling et al. 2006, p. 941). McKenzie et al. (2004, p. 893)
suggest, based on models, that the length of the fire season will
likely increase further and that fires in the western United States
will be more frequent and more severe. In particular, they found that
fire in New Mexico appears to be acutely sensitive to summer climate
and temperature changes and may respond dramatically to climate
warming.
Changes in relative humidity, especially drying over the western
United States, are also projected to increase the number of days of
high fire danger (Brown et al. 2004, p. 365). High-elevation, subalpine
forests in the Rocky Mountains typically experience infrequent (i.e.,
one to many centuries), high severity crown fires (Schoennagel et al.
2004, p. 664). These fires usually occur in association with extremely
dry regional climate patterns (Swetnam and Baisan 1994, p. 28;
Schoennagel et al. 2004, p. 664). Short drying periods do not create
the conditions appropriate for fire in these typically cool, humid
forests. Schoennagel et al. (2004, p. 665, 666) conclude that recent
increases in the area burned in subalpine forests are not attributable
to fire suppression but that variation in climate exerts the largest
influence on the size, timing, and severity of the fires. In contrast,
low-elevation, ponderosa pine forests in the Rocky Mountains were
historically characterized by frequent, low-severity fires (Schoennagel
et al. 2004, p. 669). Fire suppression has significantly increased
ladder fuels (fuels that allow fire to climb from the forest floor to
the tops of trees) and tree densities leading to unprecedented high-
severity fires in these ecosystems (Schoennagel et al. 2004, p. 669).
Rio Grande cutthroat trout streams occur in both forest types.
As discussed in the ``Fire'' section in Factor A above, because of
the observed and predicted increase in fire season length; the
predicted increase in frequency and severity of fires; the observation
that fuel treatment is only effective in low-elevation, ponderosa pine
forests; the expectation of an increase in the frequency of hot
extremes, heat waves, and heavy precipitation (IPCC 2007a, p. 15); and
the fact that most Rio Grande cutthroat trout streams occur within a
forested landscape, we conclude that wildfire associated with climate
change will exacerbate habitat loss to Rio Grande cutthroat trout
populations across their range.
Floods. The life history of salmonids is tied to the timing of
floods (Fausch et al. 2001, p. 1440). A change in timing or magnitude
of floods can scour the streambed, destroy eggs, or displace recently
emerged fry downstream (Erman et al. 1988, p. 2199; Montgomery et al.
1999, p. 378; Fausch et al. 2001, p. 1440). Floods that occur after
intense wildfires that have denuded the watershed are also a threat. As
described above, in the ``Fire'' section under Factor A, several
streams in the Southwest have had populations of trout extirpated as a
result of ash flows which occurred after fire (Rinne 1996, p. 654;
Brown et al. 2001, p. 142; Patten et al. 2007, p. 33). Consequently, an
increase in rain or snow events, intense precipitation that is
unseasonable, or precipitation that occurs after fire could extirpate
affected Rio Grande cutthroat trout populations.
In summary, extreme events, especially widespread fire and drought,
will likely affect Rio Grande cutthroat trout populations in the
foreseeable future through population extirpation, extreme population
reduction, or habitat reduction. Several Rio Grande cutthroat trout
populations have already been impacted by drought. Fire has thus far
primarily affected nonnative trout streams within the range of Rio
Grande cutthroat trout, but there is no safeguard for Rio Grande
cutthroat trout streams. The impact of a change in the timing of runoff
may be significant but is more difficult to predict.
Climate Change Summary
The extent to which climate change will affect Rio Grande cutthroat
trout is not known with certainty at this time. Preliminary projections
point to a possible rangewide negative impact through increased water
temperatures, decreased stream flow, a change in hydrograph, and an
increased occurrence of extreme events, which will all tend to
exacerbate the threats to the Rio Grande cutthroat trout and its
habitat discussed under Factors A and C above. Although the extent that
the global climate will change in the future is not known, even a
minimal increase in temperature will lead to increased habitat
unsuitability and will exacerbate most other known threats to the
subspecies.
Fisheries Management
Future management of Rio Grande cutthroat trout will depend in part
on the use of hatchery-reared fish. Although hatcheries can produce
many fish in a short period of time, the use of hatchery fish is not
without risks (Busack and Currens 1995, pp. 73-78). Two recent papers
have explored the risks of captive propagation used to supplement
species that are declining in the wild (Araki et al. 2007, Frankham
2007). Araki et al. (2007, p. 102) found that there was approximately a
40 percent decline in reproductive capabilities per captive-reared
generation when steelhead trout (Oncorhynchus mykiss) were moved to
natural environments. Frankham (2007, p. 2) notes that characteristics
selected for under captive breeding conditions are overwhelmingly
disadvantageous in the natural environment. Minimizing the number of
generations in captivity or making the captive environment similar to
the wild environment are effective means for minimizing genetic
adaptation to captivity (Frankham 2007, pp. 4, 5).
The history of brood stock management in New Mexico has been marked
by many challenges (Cowley and Pritchard 2003, pp. 12, 13). The most
recent challenges came from whirling disease infection at Seven Springs
Hatchery and the discovery that the brood stock was introgressed with
Yellowstone cutthroat trout (Patten et al. 2007, p. 42). The hatchery
was refurbished to eliminate M. cerebralis and the brood stock program
was restarted in 2005 (Patten et al. 2007, p. 42). A recently revised
brood stock management plan was completed for
[[Page 27920]]
New Mexico (Cowley and Pritchard 2003).
Although the intent of fisheries management is positive, fisheries
management may result in unanticipated outcomes. For example, Costilla
Creek restoration efforts were unfortunately marred by the introduction
of rainbow trout into the recently reclaimed stream (Patten et al.
2007, p. 101, Appendices VIII-X). The rainbow trout came from Seven
Springs Hatchery, even though this hatchery is designated as a Rio
Grande cutthroat trout facility (NMDGF 2002, p. 28; Pattten et al.
2007, p. 379). It is unclear why Seven Springs Hatchery was holding
rainbow trout. Through a coordinated effort, managers believe they
captured most, if not all, of the rainbow trout that were stocked into
Costilla Creek along with Rio Grande cutthroat trout (Patten et al.
2007, pp. 18, 102). While electrofishing to recover the rainbow trout,
two brook trout were also caught, indicating that the lower barrier was
compromised, not all the fish were killed during treatment, or that an
angler had released the fish above the barrier. In addition, because
the stocked Rio Grande cutthroat trout came from Seven Springs Hatchery
before the introgression with Yellowstone cutthroat trout was
discovered, the Rio Grande cutthroat trout that were stocked were
slightly introgressed (Patten et al. 2007, p. 102). For these reasons,
relying on hatchery-reared Rio Grande cutthroat trout does not provide
certainty that repatriation will be successful.
Fisheries managers have worked very hard in the last several years
to monitor populations, check and maintain barriers, test the genetic
purity of populations, test streams for whirling disease, fund
research, and reintroduce populations into appropriate streams (Patten
et al. 2007, pp. 4-19; Japhet et al. 2007, pp. 22-27). New populations
have been established in Costilla, South Ponil, Leandro, and Capulin
creeks in New Mexico and in Big Springs, East Costilla, and West
Costilla creeks in Colorado. Populations were restarted in Cat Creek
and Little Medano Creek, Colorado, after being lost to the drought
(Japhet et al. 2007, pp. 42-44). In addition, major restoration
projections have gone through environmental review and are in progress
on Placer Creek, Comanche Creek, and Costilla Creek. Completion of
these projects will contribute to the long-term persistence of Rio
Grande cutthroat trout. The USFS, BLM, and NPS have been active
partners in project implementation and have completed many miles of
detailed stream surveys, which adds greatly to our knowledge of habitat
condition.
New Mexico Tribes and Pueblos have recently taken initiatives to
restore Rio Grande cutthroat trout on their homelands. The Mescalero
Apache Tribe began inventorying their streams to determine presence,
and has reopened the Mescalero Tribal Fish Hatchery. The Tribe hopes to
establish a Rio Grande cutthroat trout brood stock and raise Rio Grande
cutthroat trout to support native fish restoration projects on Tribal
lands. Santa Clara Pueblo received a Tribal Wildlife grant for nearly
$200,000 for Rio Grande cutthroat trout restoration. The Pueblo is in
the initial phases of project planning for restoring the Santa Clara
Creek watershed. Nambe Pueblo has also expressed an interest in Rio
Grande cutthroat trout restoration and is working in collaboration with
USFS, the Service, Southwest Tribal Fisheries Commission (SWTFC), and
NMDGF to formulate a restoration plan to restore Rio Grande cutthroat
trout in the Nambe River watershed. The Jicarilla Apache Nation has
also been involved in Rio Grande cutthroat trout restoration and plans
to expand their restoration efforts to additional creeks on the
reservation in the near future. The SWTFC, an organization composed of
southwestern Native American tribes, has developed a Memorandum of
Understanding with NMDGF to acquire Rio Grande cutthroat trout eggs for
juvenile and adult production in support of tribal restoration Rio
Grande cutthroat trout projects. Currently, the Memorandum is still
awaiting approval by both participants. If successful, these actions
would provide further conservation for Rio Grande cutthroat trout.
The Santa Fe National Forest, led by their fisheries biologist, has
been very proactive about public education. They estimate that up until
2006 their ``Respect the Rio'' program directly reached over 9,300
people (Ferrell 2006, p. 16). They developed the Rio Grande Cutthroat
Trout Life Cycle Game, which has traveled to classrooms, Earth Day
events, and Kids' Fishing Day celebrations (Ferrell 2006, p. 15). The
game has also been translated into Spanish to reach students who speak
English as a second language. It is estimated that over 1,000 children
and adults have played the game.
In New Mexico, a Rio Grande cutthroat trout Working Group meets
monthly to discuss Rio Grande cutthroat trout conservation, projects,
and volunteer opportunities, and to coordinate and communicate efforts
among the participants. Regular members are NMDGF, the Service, Trout
Unlimited, New Mexico Trout, and the USFS. The members are committed to
Rio Grande cutthroat trout conservation.
One obstacle to fisheries managers in New Mexico has been the
difficult process of approval for chemical treatment of streams. In
August 2004, the New Mexico Game Commission voted to prohibit the use
of piscicides in New Mexico (Patten et al. 2007, p. 102). This decision
effectively terminated a project on Animas Creek, Gila National Forest,
and has made stream restoration project approval difficult. Another
obstacle to successful stream renovation is the stocking of nonnative
trout by anglers into streams that have been treated to remove them
(Japhet et al. 2007, p. 17). Although education and regulation may
help, there is no known way to stop this illegal activity.
Summary of Factor E
Fisheries management is integral to the conservation of Rio Grande
cutthroat trout. Although there are some risks associated with
fisheries management, we conclude that the benefits outweigh the risks.
We also conclude that the best scientific and commercial information
available to us indicates that the threats facing Rio Grande cutthroat
trout will be exacerbated by climate change. Continued management
actions to connect fragmented populations are essential. However, at
this time, it is not clear that management actions can outpace some of
the projected effects of climate change.
Finding
We have carefully assessed the best scientific and commercial
information available regarding the past, present, and future threats
faced by Rio Grande cutthroat trout. We have reviewed information
supplied to us by State and Federal agencies, peer-reviewed literature,
comments from private citizens, and other unpublished documents. The
information summarized in this status review includes substantial
information that was not available at the time of our 2002 finding (67
FR 39936). On the basis of this review, we find that listing of Rio
Grande cutthroat trout as threatened or endangered is warranted, due to
a combination of population fragmentation, isolation, small population
size, nonnative trout, drought, and fire. We anticipate these threats
will be compounded by the projected effects of climate change. However,
listing of the Rio Grande cutthroat trout is precluded at this time by
pending proposals for other species with higher listing priorities and
actions.
[[Page 27921]]
In the context of the Act, the term ``threatened species'' means
any species (or subspecies or, for vertebrates, distinct population
segments) that is likely to become an endangered species within the
foreseeable future throughout all or a significant portion of its
range. The term ``endangered species'' means any species that is in
danger of extinction throughout all or a significant portion of its
range. The Act does not indicate threshold levels of historic
population size at which, as the population of a species declines,
listing as either ``threatened'' or ``endangered'' becomes warranted.
Instead, the principal considerations in the determination of whether
or not a species warrants listing as a threatened or an endangered
species under the Act are the threats that now confront the species and
the probability that the species will persist into ``the foreseeable
future.'' The Act does not define the term ``foreseeable future.''
However, we consider the ``foreseeable future'' to be 20 to 30 years,
which equates to approximately 4 to 10 Rio Grande cutthroat trout
generations, depending on the productivity of the environment. We find
that this is both reasonable and appropriate for the present status
review because it is long enough to take into account multi-
generational dynamics of life-history and ecological adaptation, yet
short enough to incorporate social and political change that affects
species management.
Evidence shows that populations of Rio Grande cutthroat trout have
been greatly reduced over the last 200 years. The range of Rio Grande
cutthroat trout has contracted northward and populations are primarily
restricted to high-elevation headwater streams. We attribute the
decline in the distribution of Rio Grande cutthroat trout to habitat
degradation and the introduction of nonnative sport fish into Rio
Grande cutthroat trout habitat that began in the late 1800s. The wide
distribution of rainbow trout and nonnative cutthroat trout have
compromised Rio Grande cutthroat trout populations through competition,
hybridization, and predation. These introduced fish have expanded and
colonized new habitat and formed naturally reproducing populations that
occupy the former, and in some cases current, range of Rio Grande
cutthroat trout.
We find that populations we considered secure in 2002 suffered
severe to moderate population declines. We considered 13 populations
secure in 2002, and now we find that only 8 populations (5 identified
in 2002, 3 new populations) would meet our definition of long-term
persistence (over 2,500 fish, 9.6 km (6 mi) of occupied habitat, no
nonnatives present). Although 97 additional conservation populations
exist, they all are affected by one or more threats (e.g., small
population size, short stream length, poor habitat quality, nonnative
trout) that we consider significant enough to threaten their long-term
survival. The overarching threat that magnifies the problems for each
individual population is fragmentation. Over 90 percent of Rio Grande
cutthroat trout populations exist in stream fragments. Consequently,
recolonization of streams cannot occur after a natural disaster occurs
and populations are much more susceptible to extirpation.
Because of the increases in air temperature that have already been
documented in the Southwest, and other changes that have been
documented in hydrology, fire patterns, and the life history of animals
in the region, there is evidence that the effects of climate change are
already occurring in the range of Rio Grande cutthroat trout. Every
aspect of climate change we examined will likely have a negative effect
on Rio Grande cutthroat trout. Rio Grande cutthroat trout populations
are currently surviving with multiple stressors. Adding the effects of
climate change on these populations may exacerbate the existing threats
and stressors on the species.
There is documented commitment of agency personnel, tribes, and
private landowners to continue conservation efforts for Rio Grande
cutthroat trout. This is evidenced by the lists of accomplishments the
States and agencies have provided to us. Both State and Federal
agencies have been actively involved in Rio Grande cutthroat trout
management. Several habitat restoration projects are in progress and
several others are planned. It is too early to determine the level of
success of current large watershed projects as they have not been fully
completed and evaluated.
Listing Priority Number
In accordance with guidance we published on September 21, 1983, we
assign a Listing Priority Number (LPN) to each candidate species (48 FR
43098). Such a priority ranking guidance system is required under
section 4(h)(3) of the Act (16 U.S.C. 1533(h)(3)). Using this guidance,
we assign each candidate an LPN of 1 to 12, depending on the magnitude
of threats (high vs. moderate to low); immediacy of threats (imminent
or non-imminent); and taxonomic status of the species, in order of
priority (monotypic genus (i.e., a species that is the sole member of a
genus), species, subspecies, distinct population segment, or
significant portion of the range). The lower the listing priority
number, the higher the listing priority (that is, a species with an LPN
of 1 would have the highest listing priority).
Many of the threats to this subspecies could result in complete
loss of a given population at any time (e.g., fire, disease, nonnative
introgression). However, because there are many known conservation
populations and because many populations are being actively managed,
the threats to this subspecies as a whole are considered moderate.
An increase in average mean air temperature of just over 1 [deg]C
(2.5 [deg]F) in Arizona and just under 1 [deg]C (1.8 [deg]F) in New
Mexico since 1976 (Parmesan and Galbraith 2004, pp. 18, 19; State of
New Mexico 2006, p. 5; Lenart 2007, p. 4) suggest that climate change
is already occurring in the Southwest. Coldwater species like Rio
Grande cutthroat trout are expected to be among the most sensitive
species to climate change. Water temperatures in some Rio Grande
cutthroat trout streams are already elevated beyond recommended
temperatures for coldwater trout. At least 14 Rio Grande cutthroat
trout streams either dried up or had populations negatively affected by
the 2002 drought. Rio Grande cutthroat trout populations already face
multiple stresses such as nonnative trout, fragmented habitat, and
limited habitat. The additional effects of climate change are expected
to cause population extirpations and population bottlenecks.
Consequently, threats to this species are considered imminent.
Therefore, based on the moderate magnitude and immediacy of threats, we
have given this subspecies an LPN of 9.
Preclusion and Expeditious Progress
Preclusion is a function of the listing priority of a species in
relation to the resources that are available and competing demands for
those resources. Thus, in any given fiscal year (FY), multiple factors
dictate whether it will be possible to undertake work on a proposed
listing regulation or whether promulgation of such a proposal is
warranted but precluded by higher priority listing actions.
The resources available for listing actions are determined through
the annual Congressional appropriations process. The appropriation for
the Listing Program is available to support work involving the
following listing actions: proposed and final listing rules; 90-day and
12-month findings on petitions to add species to the Lists of
Endangered and Threatened Wildlife and Plants (Lists) or to change the
status
[[Page 27922]]
of a species from threatened to endangered; annual determinations on
prior ``warranted but precluded'' petition findings as required under
section 4(b)(3)(C)(i) of the Act; proposed and final rules designating
critical habitat; and litigation-related, administrative, and program
management functions (including preparing and allocating budgets,
responding to Congressional and public inquiries, and conducting public
outreach regarding listing and critical habitat). The work involved in
preparing various listing documents can be extensive and may include,
but is not limited to: gathering and assessing the best scientific and
commercial data available and conducting analyses used as the basis for
our decisions; writing and publishing documents; and obtaining,
reviewing, and evaluating public comments and peer review comments on
proposed rules and incorporating relevant information into final rules.
The number of listing actions that we can undertake in a given year
also is influenced by the complexity of those listing actions; that is,
more complex actions generally are more costly. For example, during the
past several years, the cost (excluding publication costs) for
preparing a 12-month finding, without a proposed rule, has ranged from
approximately $11,000 for one species with a restricted range and
involving a relatively uncomplicated analysis to $305,000 for another
species that is wide-ranging and involving a complex analysis.
We cannot spend more than is appropriated for the Listing Program
without violating the Anti-Deficiency Act (see 31 U.S.C.
1341(a)(1)(A)). In addition, in FY 1998 and for each fiscal year since
then, Congress has placed a statutory cap on funds which may be
expended for the Listing Program, equal to the amount expressly
appropriated for that purpose in that fiscal year. This cap was
designed to prevent funds appropriated for other functions under the
Act (for example, recovery funds for removing species from the Lists),
or for other Service programs, from being used for Listing Program
actions (see House Report 105-163, 105th Congress, 1st Session, July 1,
1997).
Recognizing that designation of critical habitat for species
already listed would consume most of the overall Listing Program
appropriation, Congress also put a critical habitat subcap in place in
FY 2002 and has retained it each subsequent year to ensure that some
funds are available for other work in the Listing Program: ``The
critical habitat designation subcap will ensure that some funding is
available to address other listing activities'' (House Report No. 107-
103, 107th Congress, 1st Session, June 19, 2001). In FY 2002 and each
year until FY 2006, the Service has had to use virtually the entire
critical habitat subcap to address court-mandated designations of
critical habitat, and consequently none of the critical habitat subcap
funds have been available for other listing activities. In FY 2007, we
were able to use some of the critical habitat subcap funds to fund
proposed listing determinations for high-priority candidate species; we
expect to also be able to do this in FY 2008.
Thus, through the listing cap, the critical habitat subcap, and the
amount of funds needed to address court-mandated critical habitat
designations, Congress and the courts have in effect determined the
amount of money available for other listing activities. Therefore, the
funds in the listing cap, other than those needed to address court-
mandated critical habitat for already listed species, set the limits on
our determinations of preclusion and expeditious progress.
Congress also recognized that the availability of resources was the
key element in deciding whether, when making a 12-month petition
finding, we would prepare and issue a listing proposal or make a
``warranted but precluded'' finding for a given species. The Conference
Report accompanying Public Law 97-304, which established the current
statutory deadlines and the warranted-but-precluded finding, states (in
a discussion on 90-day petition findings that by its own terms also
covers 12-month findings) that the deadlines were ``not intended to
allow the Secretary to delay commencing the rulemaking process for any
reason other than that the existence of pending or imminent proposals
to list species subject to a greater degree of threat would make
allocation of resources to such a petition [that is, for a lower-
ranking species] unwise.''
In FY 2008, expeditious progress is that amount of work that can be
achieved with $8,206,940, which is the amount of money that Congress
appropriated for the Listing Program at this time (that is, the portion
of the Listing Program funding not related to critical habitat
designations for species that are already listed). Our process is to
make our determinations of preclusion on a nationwide basis to ensure
that the species most in need of listing will be addressed first and
also because we allocate our listing budget on a nationwide basis. The
$8,206,940 for listing activities (that is, the portion of the Listing
Program funding not related to critical habitat designations for
species that already are listed) will be used to fund work in the
following categories: Compliance with court orders and court-approved
settlement agreements requiring that petition findings or listing
determinations be completed by a specific date; section 4 (of the Act)
listing actions with absolute statutory deadlines; essential
litigation-related, administrative, and program management functions;
and high-priority listing actions. The allocations for each specific
listing action are identified in the Service's FY 2008 Draft Allocation
Table (part of our administrative record). We are working on completing
our allocation at this time. More funds are available in FY 2008 than
in previous years to work on listing actions that are not the subject
of court orders or court-approved settlement agreements.
We currently have more than 120 species with an LPN of 2.
Therefore, we further rank the candidate species with an LPN of 2 by
using the following extinction-risk type criteria: International Union
for the Conservation of Nature and Natural Resources (IUCN) Red list
status/rank, Heritage rank (provided by NatureServe), Heritage threat
rank (provided by NatureServe), and species currently with fewer than
50 individuals, or 4 or fewer populations. Those species with the
highest IUCN rank (critically endangered), the highest Heritage rank
(G1), the highest Heritage threat rank (substantial, imminent threats),
and currently with fewer than 50 individuals, or fewer than 4
populations, comprise a list of approximately 40 candidate species
(``Top 40''). These 40 candidate species have the highest priority to
receive funding to work on a proposed listing determination. To be more
efficient in our listing process, as we work on proposed rules for
these species in the next several years, we are preparing multi-species
proposals when appropriate, and these may include species with lower
priority if they overlap geographically or have the same threats as a
species with an LPN of 2. In addition, available staff resources are
also a factor in determining high-priority species provided with
funding. Finally, proposed rules for reclassification of threatened
species to endangered are lower priority, since the listing of the
species already affords the protection of the Act and implementing
regulations. We assigned the Rio Grande cutthroat trout an LPN of 9,
based on our finding that the subspecies faces
[[Page 27923]]
threats of moderate magnitude that are imminent.
As explained above, a determination that listing is warranted but
precluded must also demonstrate that expeditious progress is being made
to add or remove qualified species to and from the Lists of Endangered
and Threatened Wildlife and Plants. (We note that we do not discuss
specific actions taken on progress towards removing species from the
Lists because that work is conducted using appropriations for our
Recovery program, a separately budgeted component of the Endangered
Species Program. As explained above in our description of the statutory
cap on Listing Program funds, the Recovery Program funds and actions
supported by them cannot be considered in determining expeditious
progress made in the Listing Program.) As with our ``precluded''
finding, expeditious progress in adding qualified species to the Lists
is a function of the resources available and the competing demands for
those funds. Our expeditious progress in FY 2007 in the Listing
Program, up to the date of making this finding for the Rio Grande
cutthroat trout, included preparing and publishing the following
determinations:
FY 2007 Completed Listing Actions
----------------------------------------------------------------------------------------------------------------
Publication date Title Actions FR pages
----------------------------------------------------------------------------------------------------------------
10/11/2006..................... Withdrawal of the Final withdrawal, 71 FR 59700-59711.
Proposed Rule to List Threats eliminated.
the Cow Head Tui Chub
(Gila biocolor
vaccaceps) as Endangered.
10/11/2006..................... Revised 12-Month Finding Notice of 12-month 71 FR 59711-59714.
for the Beaver Cave petition finding,
Beetle Not warranted.
(Pseudanophthalmus
major).
11/14/2006..................... 12-Month Finding on a Notice of 12-month 71 FR 66292-66298.
Petition to List the petition finding,
Island Marble Butterfly Not warranted.
(Euchloe ausonides
insulanus) as Threatened
or Endangered.
11/14/2006..................... 90-Day Finding for a Notice of 90-day 71 FR 66298-66301.
Petition to List the petition finding,
Kennebec River Substantial.
Population of Anadromous
Atlantic Salmon as Part
of the Endangered Gulf
Of Maine Distinct
Population Segment.
11/21/2006..................... 90-Day Finding on a Notice of 90-day 71 FR 67318-67325.
Petition To List the petition finding,
Columbian Sharp-Tailed Not substantial.
Grouse as Threatened or
Endangered.
12/5/2006...................... 90-Day Finding on a Notice of 90-day 71 FR 70483-70492.
Petition To List the petition finding,
Tricolored Blackbird as Not substantial.
Threatened or Endangered.
12/6/2006...................... 12-Month Finding on a Notice of 12-month 71 FR 70717-70733.
Petition To List the petition finding,
Cerulean Warbler Not warranted.
(Dendroica cerulea) as
Threatened with Critical
Habitat.
12/6/2006...................... 90-Day Finding on a Notice of 90-day 71 FR 70715-70717.
Petition To List the Petition Finding,
Upper Tidal Potomac Not substantial.
River Population of the
Northern Water Snake
(Nerodia sipedon) as an
Endangered Distinct
Population Segment.
12/14/2006..................... 90-Day Finding on a Notice of 5-year 71 FR 75215-75220.
Petition to Remove the Review, Initiation.
Uinta Basin Hookless Notice of 90-day
Cactus From the List of petition finding,
Endangered and Not substantial.
Threatened Plants; 90- Notice of 90-day
Day Finding on a petition finding,
Petition To List the Substantial.
Pariette Cactus as
Threatened or Endangered.
12/19/2006..................... Withdrawal of Proposed Notice of 71 FR 76023-76035.
Rule to List Penstemon withdrawal, More
grahamii (Graham's abundant than
beardtongue) as believed, or
Threatened With Critical diminished threats.
Habitat.
12/19/2006..................... 90-Day Finding on Notice of 90-day 71 FR 76057-76079.
Petitions to List the petition finding,
Mono Basin Area Not substantial.
Population of the
Greater Sage-Grouse as
Threatened or Endangered.
1/9/2007....................... 12-Month Petition Finding Notice of 12-month 72 FR 1063-1099.
and Proposed Rule To petition finding,
List the Polar Bear Warranted.
(Ursus maritimus) as Proposed Listing,
Threatened Throughout Threatened.
Its Range; Proposed Rule.
1/10/2007...................... Endangered and Threatened Clarification of 72 FR 1186-1189.
Wildlife and Plants; findings.
Clarification of
Significant Portion of
the Range for the
Contiguous United States
Distinct Population
Segment of the Canada
Lynx.
1/12/2007...................... Withdrawal of Proposed Notice of 72 FR 1621-1644.
Rule To List Lepidium withdrawal, More
papilliferum (Slickspot abundant than
Peppergrass). believed, or
diminished threats.
2/2/2007....................... 12-Month Finding on a Notice of 12-month 72 FR 4967-4997.
Petition To List the petition finding,
American Eel as Not warranted.
Threatened or Endangered.
2/13/2007...................... 90-Day Finding on a Notice of 90-day 72 FR 6699-6703.
Petition To List the petition finding,
Jollyville Plateau Substantial.
Salamander as Endangered.
2/13/2007...................... 90-Day Finding on a Notice of 90-day 72 FR 6703-6707.
Petition To List the San petition finding,
Felipe Gambusia as Not substantial.
Threatened or Endangered.
2/14/2007...................... 90-Day Finding on A Notice 90-day 72 FR 6998-7005.
Petition to List petition finding,
Astragalus debequaeus Not substantial.
(DeBeque milkvetch) as
Threatened or Endangered.
2/21/2007...................... 90-Day Finding on a Notice of 5-year 72 FR 7843-7852.
Petition To Reclassify Review, Initiation.
the Utah Prairie Dog Notice of 90-day
From Threatened to petition finding,
Endangered and Not substantial.
Initiation of a 5-Year
Review.
3/8/2007....................... 90-Day Finding on a Notice of 90-day 72 FR 10477-10480.
Petition To List the petition finding,
Monongahela River Basin Not substantial.
Population of the
Longnose Sucker as
Endangered.
3/29/2007...................... 90-Day Finding on a Notice 90-day 72 FR 14750-14759.
Petition To List the petition finding,
Siskiyou Mountains Substantial.
Salamander and Scott Bar
Salamander as Threatened
or Endangered.
[[Page 27924]]
4/24/2007...................... Revised 12-Month Finding Notice of 12-month 72 FR 20305-20314.
for Upper Missouri River petition finding,
Distinct Population Not warranted.
Segment of Fluvial
Arctic Grayling.
5/2/2007....................... 12-Month Finding on a Notice of 12-month 72 FR 24253-24263.
Petition to List the petition finding,
Sand Mountain Blue Not warranted.
Butterfly (Euphilotes
pallescens ssp.
arenamontana) as
Threatened or Endangered
with Critical Habitat.
5/22/2007...................... Status of the Rio Grande Notice of Review.... 72 FR 28664-28665.
Cutthroat Trout.
5/30/2007...................... 90-Day Finding on a Notice of 90-day 72 FR 29933-29941.
Petition To List the Mt. petition finding,
Charleston Blue Substantial.
Butterfly as Threatened
or Endangered.
6/5/2007....................... 12-Month Finding on a Notice of Review.... 72 FR 31048-31049.
Petition To List the
Wolverine as Threatened
or Endangered.
6/6/2007....................... 90-Day Finding on a Notice 90-day 72 FR 31256-31264.
Petition To List the Petition Finding,
Yellow-Billed Loon as Substantial.
Threatened or Endangered.
6/13/2007...................... 12-Month Finding for a Notice 12-month 72 FR 32589-32605.
Petition To List the petition finding,
Colorado River Cutthroat Not warranted.
Trout as Threatened or
Endangered.
6/25/2007...................... 12-Month Finding on a Notice amended 12- 72 FR 34657-34661.
Petition To List the month petition
Sierra Nevada Distinct finding, Warranted
Population Segment of but precluded.
the Mountain Yellow-
Legged Frog (Rana
muscosa).
7/5/2007....................... 12-Month Finding on a Notice 12-month 72 FR 36635-36646.
Petition To List the petition finding,
Casey's June Beetle Warranted but
(Dinacoma caseyi) as precluded.
Endangered With Critical
Habitat.
8/15/2007...................... 90-Day Finding on a Notice 90-day 72 FR 45717-45722.
Petition To List the Petition Finding,
Yellowstone National Not substantial.
Park Bison Herd as
Endangered.
08/16/2007..................... 90-Day Finding on a Notice 90-day 72 FR 46023-46030.
Petition To List Petition Finding,
Astragalus anserinus Substantial.
(Goose Creek milk-vetch)
as Threatened or
Endangered.
8/28/2007...................... 12-Month Finding on a Notice of Review.... 72 FR 49245-49246.
Petition To List the
Gunnison's Prairie Dog
as Threatened or
Endangered.
9/11/2007...................... 90-Day Finding on a Notice 90-day 72 FR 51766-51770.
Petition To List Kenk's Petition Finding,
Amphipod, Virginia Well Not substantial.
Amphipod, and the
Copepod Acanthocyclops
columbiensis as
Endangered.
9/18/2007...................... 12-month Finding on a Notice 12-month 72 FR 53211-53222.
Petition To List petition finding
Sclerocactus brevispinus for uplisting,
(Pariette cactus) as an Warranted but
Endangered or Threatened precluded.
Species; Taxonomic
Change From Sclerocactus
glaucus to Sclerocactus
brevispinus, S. glaucus,
and S. wetlandicus.
----------------------------------------------------------------------------------------------------------------
In FY 2007, we provided funds to work on proposed listing
determinations for the following high-priority species: 3 southeastern
aquatic species (Georgia pigtoe, interrupted rocksnail, and rough
hornsnail), 2 Oahu plants (Doryopteris takeuchii, Melicope hiiakae), 31
Kauai species (Kauai creeper, Drosophila attigua, Astelia waialealae,
Canavalia napaliensis, Chamaesyce eleanoriae, Chamaesyce remyi var.
kauaiensis, Chamaesyce remyi var. remyi, Charpentiera densiflora,
Cyanea eleeleensis, Cyanea kuhihewa, Cyrtandra oenobarba, Dubautia
imbricata ssp. imbricata, Dubautia plantaginea ssp. magnifolia,
Dubautia waialealae, Geranium kauaiense, Keysseria erici, Keysseria
helenae, Labordia helleri, Labordia pumila, Lysimachia daphnoides,
Melicope degeneri, Melicope paniculata, Melicope puberula, Myrsine
mezii, Pittosporum napaliense, Platydesma rostrata, Pritchardia hardyi,
Psychotria grandiflora, Psychotria hobdyi, Schiedea attenuata,
Stenogyne kealiae), 4 Hawaiian damselflies (Megalagrion nesiotes,
Megalagrion leptodemas, Megalagrion oceanicum, Megalagrion pacificum),
and one Hawaiian plant (Phyllostegia hispida (no common name)). In FY
2008, we are continuing to work on these listing proposals (we are now
including an additional 17 species in the Kauai species proposed
listing determination package). In addition, we are continuing to work
on several other determinations listed below, which we funded in FY
2007 and are scheduled to complete in FY 2008.
Actions Funded in FY 2007 That Have Yet To Be Completed
------------------------------------------------------------------------
Species Action
------------------------------------------------------------------------
Actions Subject to Court Order/
Settlement Agreement:
Western sage grouse................ 90-day petition finding
(remand).
Actions with Statutory Deadlines:
Polar bear......................... Final listing determination.
Ozark chinquapin................... 90-day petition finding.
Tucson shovel-nosed snake.......... 90-day petition finding.
Gopher tortoise--Florida population 90-day petition finding.
Sacramento valley tiger beetle..... 90-day petition finding.
Eagle lake trout................... 90-day petition finding.
Smooth billed ani.................. 90-day petition finding.
Mojave ground squirrel............. 90-day petition finding.
Gopher Tortoise--eastern population 90-day petition finding.
Bay Springs salamander............. 90-day petition finding.
Tehachapi slender salamander....... 90-day petition finding.
[[Page 27925]]
Evening primrose................... 90-day petition finding.
Northern leopard frog.............. 90-day petition finding.
Cactus ferruginous pygmy owl....... 90-day petition finding.
------------------------------------------------------------------------
Our expeditious progress so far in FY 2008 in the Listing Program,
includes preparing and publishing the following:
FY 2008 Completed Listing Actions
----------------------------------------------------------------------------------------------------------------
Publication date Title Actions FR pages
----------------------------------------------------------------------------------------------------------------
10/09/2007..................... 90-Day Finding on a Notice of 90-day 72 FR 57278-57283.
Petition To List the Petition Finding,
Black-Footed Albatross Substantial.
(Phoebastria nigripes)
as Threatened or
Endangered.
10/09/2007..................... 90-Day Finding on a Notice of 90-day 72 FR 57273-57276.
Petition To List the Petition Finding,
Giant Palouse Earthworm Not Substantial.
as Threatened or
Endangered.
10/23/2007..................... 90-Day Finding on a Notice of 90-day 72 FR 59983-59989.
Petition To List the Petition Finding,
Mountain Whitefish Not Substantial.
(Prosopium williamsoni)
in the Big Lost River,
ID, as Threatened or
Endangered.
10/23/2007.................... 90-Day Finding on a Notice of 90-day 72 FR 59979-59983.
Petition To List the Petition Finding,
Summer-Run Kokanee Not substantial.
Population in Issaquah
Creek, WA, as Threatened
or Endangered.
11/08/2007..................... Response to Court on Response to Court... 72 FR 63123-63140.
Significant Portion of
the Range, and
Evaluation of Distinct
Population Segments, for
the Queen Charlotte
Goshawk.
12/13/2007..................... 12-Month Finding on a Notice of 12-month 72 FR 71039-71054.
Petition To List the Petition Finding,
Jollyville Plateau Warranted but
Salamander (Eurycea Precluded.
tonkawae) as Endangered
With Critical Habitat.
1/08/2008...................... 90-Day Finding on a Notice of 90-day 73 FR 1312-1313.
Petition To List the Petition Finding,
Pygmy Rabbit Substantial.
(Brachylagus idahoensis)
as Threatened or
Endangered.
1/10/2008...................... 90-Day Finding on Notice of 90-day 73 FR 1855-1861.
Petition To List the Petition Finding,
Amargosa River Substantial.
Population of the Mojave
Fringe-Toed Lizard (Uma
scoparia) as Threatened
or Endangered With
Critical Habitat.
1/24/2008...................... 12-Month Finding on a Notice of 12-month 73 FR 4379-4418.
Petition To List the Petition Finding,
Siskiyou Mountains Not Warranted.
Salamander (Plethodon
stormi) and Scott Bar
Salamander (Plethodon
asupak) as Threatened or
Endangered.
2/05/2008...................... 12-Month Finding on a Notice of 12-month 73 FR 6660-6684.
Petition To List the Petition Finding,
Gunnison's Prairie Dog Warranted.
as Threatened or
Endangered.
2/07/2008...................... 12-Month Finding on a Notice of Review.... 73 FR 7236-7237.
Petition To List the
Bonneville Cutthroat
Trout (Oncorhynchus
clarki utah) as
Threatened or Endangered.
2/19/2008...................... Listing Phyllostegia Proposed Listing, 73 FR 9078-9085.
hispida (No Common Name) Endangered.
as Endangered Throughout
Its Range.
2/26/2008...................... Initiation of Status Notice of Review.... 73 FR 10218-10219.
Review for the Greater
Sage-Grouse
(Centrocercus
urophasianus) as
Threatened or Endangered.
3/11/2008...................... 12-Month Finding on a Notice of 12-month 73 FR 12929-12941.
Petition To List the Petition Finding,
North American Wolverine Not Warranted.
as Endangered or
Threatened.
3/20/2008...................... 90-Day Finding on a Notice of 90-day 73 FR 14950-14955.
Petition To List the Petition Finding,
U.S. Population of Substantial.
Coaster Brook Trout
(Salvelinus fontinalis)
as Endangered.
----------------------------------------------------------------------------------------------------------------
Our expeditious progress also includes work on listing actions,
which we are funding in FY 2008. These actions are listed below. We are
conducting work on those actions in the top section of the table under
a deadline set by a court. Actions in the middle section of the table
are being conducted to meet statutory timelines, that is, timelines
required under the Act. Actions in the bottom section of the table are
high priority listing actions, which include at least one or more
species with an LPN of 2, available staff resources, and, when
appropriate, species with a lower priority if they overlap
geographically or have the same threats as the species with the high
priority.
Actions Funded in FY 2008 That Have Yet To Be Completed
------------------------------------------------------------------------
Species Action
------------------------------------------------------------------------
Actions Subject to Court Order/
Settlement Agreement:
Bonneville cutthroat trout......... 12-month petition finding
(remand).
Mexican garter snake............... 12-month petition finding
(remand).
Actions with Statutory Deadlines:
Polar bear......................... Final listing determination.
[[Page 27926]]
Phyllostegia hispida............... Final listing.
Yellow-billed loon................. 12-month petition finding.
Black-footed albatross............. 12-month petition finding.
Mount Charleston blue butterfly.... 12-month petition finding.
Goose Creek milk-vetch............. 12-month petition finding.
Mojave fringe-toed lizard.......... 12-month petition finding.
White-tailed prairie dog........... 12-month petition finding.
Pygmy rabbit (rangewide)........... 12-month petition finding.
Delta smelt (uplisting)............ 90-day petition finding.
Mono Basin sage grouse (vol. 90-day petition finding.
remand).
Ashy storm petrel.................. 90-day petition finding.
Longfin smelt--San Fran. Bay 90-day petition finding.
population.
Black-tailed prairie dog........... 90-day petition finding.
Lynx (include New Mexico in 90-day petition finding.
listing).
Wyoming pocket gopher.............. 90-day petition finding.
Llanero coqui...................... 90-day petition finding.
Least chub......................... 90-day petition finding.
American pika...................... 90-day petition finding.
Dusky tree vole.................... 90-day petition finding.
Sacramento Mts. checkerspot 90-day petition finding.
butterfly.
Kokanee--Lake Sammamish population. 90-day petition finding.
206 species........................ 90-day petition finding.
475 Southwestern species........... 90-day petition finding.
High Priority Listing Actions:
48 Kauai species \1\............... Proposed listing.
21 Kauai species................... Proposed listing.
11 packages of high-priority Proposed listing.
candidate species.
Flatwoods salamander (taxonomic Proposed listing.
revision).
------------------------------------------------------------------------
\1\ Funds used for this listing action were also provided in FY 2007.
We have endeavored to make our listing actions as efficient and
timely as possible, given the requirements of the relevant law and
regulations, and constraints relating to workload and personnel. We are
continually considering ways to streamline processes or achieve
economies of scale, such as by batching related actions together. Given
our limited budget for implementing section 4 of the Act, these actions
described above collectively constitute expeditious progress.
We will list the Rio Grande cutthroat trout as threatened or
endangered when funding is available for discretionary listing actions.
We intend any listing action for the Rio Grande cutthroat trout to be
as accurate as possible. Therefore, we will continue to accept
additional information and comments on the status of and threats to
this subspecies from all concerned governmental agencies, the
scientific community, industry, or any other interested party
concerning this finding. If an emergency situation develops with this
subspecies that warrants an emergency listing, we will act immediately
to provide additional protection.
References Cited
A complete list of all references cited in this document is
available from the New Mexico Ecological Services Field Office (see
ADDRESSES section).
Author
The primary author of this notice is the staff of the Albuquerque
Ecological Services Field Office, 2105 Osuna Road NE., Albuquerque, NM
87113.
Authority: The authority for this action is the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: April 30, 2008.
Kenneth Stansell,
Director, Fish and Wildlife Service.
[FR Doc. E8-10182 Filed 5-13-08; 8:45 am]
BILLING CODE 4310-55-P