Endangered and Threatened Wildlife and Plants; Status Review for Rio Grande Cutthroat Trout, 27900-27926 [E8-10182]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 73, Number 94 (Wednesday, May 14, 2008)]
[Proposed Rules]
[Pages 27900-27926]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-10182]



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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

Federal Register / Vol. 73, No. 94 / Wednesday, May 14, 2008 / 
Proposed Rules

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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 https://
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

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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 a