[Federal Register: June 11, 2002 (Volume 67, Number 112)]
[Proposed Rules]               
[Page 39936-39947]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; Candidate Status 
Review for Rio Grande Cutthroat Trout

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of candidate status review.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service) announce the 
results of the candidate status review for the Rio Grande cutthroat 
trout (Onchorhynchus clarki virginalis) under the Endangered Species 
Act of 1973, as amended. After a review of all available scientific and 
commercial information, we have determined that listing of the Rio 
Grande cutthroat trout is not warranted at this time.

DATES: The finding announced in this document was made on June 3, 2002.

ADDRESSES: You may submit comments regarding this notice to the 
Supervisor, U.S. Fish and Wildlife Service, New Mexico Ecological 
Services Field Office, 2105 Osuna Road NE, Albuquerque, New Mexico 
87113. Written comments and materials received in response to this 
notice will be available for public inspection, by appointment, during 
normal business hours at the New Mexico Field Office.

Supervisor, U.S. Fish and Wildlife Service, 2105 Osuna Road NE, 
Albuquerque, New Mexico 87113. (505) 346-2525 ext 106.



    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. 
Section 4(b)(3)(B) of the Endangered Species Act (Act) requires that we 
make a finding on whether a petition to list, delist or reclassify a 
species presents substantial scientific or commercial information 
indicating that the petitioned action is--(a) not warranted; (b) 
warranted; or (c) warranted but precluded by listing proposals of 
higher priority. 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 challenging the September 14, 1998, 90-day 
petition finding as violating the Act and the Administrative Procedures 
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 species 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 stipulates that we will initiate a candidate status review 
for the Rio Grande cutthroat trout. The settlement also stipulates that 
on or before June 3, 2002, we will make a determination concerning the 
results of this review and, shortly thereafter, we will publish our 
determination in the Federal Register. The agreement also states that 
we will not vacate our previous determination in the interim.

Biogeography and Taxonomy

    The Rio Grande cutthroat trout (RGCT) is a subspecies of cutthroat 
trout, endemic to the Rio Grande, Pecos, and possibly the Canadian 
River Basins in New Mexico and Colorado. The first specimens that were 
collected for scientific purposes came from Ute Creek in Costilla 
County, Colorado. Girard described these fish as Salar virginalis in 
1856 (Behnke 1967). Cutthroat trout are distinguished by the red to 
orange slashes in the throat folds beneath the lower jaw. Rio Grande 
cutthroat trout have irregular shaped spots that are concentrated 
behind the dorsal fin (largest fin on the back), smaller less numerous 
spots located primarily above the lateral line anterior to the dorsal 
fin, and basibranchial (located on the floor of the gill chamber) teeth 
that are minute or absent. Rio Grande cutthroat trout are light rose to 
red-orange on the sides and pink or yellow-orange on the belly.
    The historical distribution of RGCT is not known with certainty. In 
general, it is assumed that RGCT occupied all streams capable of 
supporting trout in the Rio Grande and Pecos basins (Stumpff and Cooper 
1996). It is unclear if RGCT were also present in the Canadian River 
Basin. The Pecos River is a tributary of the Rio Grande, so a historic 
connection between RGCT in the two basins is possible. 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. However, because trout were moved and stocked frequently 
beginning in the 1800s, the difficulties in correctly identifying fish, 
and errors in locality records make it difficult to know if early 
reports of trout from the Canadian River headwaters were indeed RGCT. 
Genetic testing of RGCT from the three basins using

[[Page 39937]]

molecular methods has not yet clarified the situation, but research 
continues on this subject (pers. comm., Yvette Paroz, New Mexico 
Department of Game and Fish (NMDGF), 2002). Biologists have suggested 
that RGCT may have occurred in Texas (Garrett and Matlock 1991) and 
Mexico (Behnke 1967). Currently, the southern most distribution of RGCT 
occurs in Animas Creek, Sierra County, New Mexico, and Indian Creek on 
the Mescalero Apache Indian Reservation in Otero County, New Mexico.

Life History

    Because the RGCT has not been studied intensively, less is known 
specifically about their habitat requirements or life history 
characteristics than is known for several other subspecies of cutthroat 
trout. As is true of other subspecies of cutthroat trout, it is found 
in clear, cold streams. Unlike some subspecies of cutthroat trout, such 
as the Bonneville (O. c. utah) and Yellowstone (O. c. bouvieri), RGCT 
did not originally inhabit large lake systems. However, they have been 
introduced into coldwater lakes and reservoirs. They spawn as high 
flows from snowmelt recede, typically from the middle of May to the 
middle of June in New Mexico (NMDGF 2002). Spawning is probably keyed 
to day length, water temperature, elevation, and runoff (Stumpff 1998, 
Sublette et al. 1990). The size of mature females ranges from 10.7-26 
centimeters (4.21-10.27 inches (in)) (Stumpff 1998). Number of eggs per 
female varies greatly depending on the size and age of the fish. 
Stumpff (1998) reported that average egg production from 93 females 
spawned from Rio Puerco, New Mexico, was less than 100 eggs per female; 
however, these fish may have been collected after the peak of the 
spawn. From efforts to develop RGCT broodstock, fish from several 
streams were collected and spawned from 1994 to 1997. The average 
number of eggs per female from these collections was 175 (Stumpff 
1998). The mean number of eggs taken from 12 RGCT from Indian Creek 
(Tularosa Basin) was 311 with the range between 232-454 (Cowley 1993). 
Sublette et al. (1990) state that females produce between 200-4,500 
eggs; however, this figure applies to all cutthroat subspecies and is 
not specific to RGCT.
    It is unknown if RGCT spawn every year or if some portion of the 
population spawns every other year as has been recorded for westslope 
cutthroat trout (O. c. lewisi) (McIntyre and Rieman 1995). 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). Sex ratio is also unknown, but a ratio skewed towards 
more females might be expected (Cowley 1993). Although Yellowstone 
(Gresswell 1995), Colorado River (O. c. pleuriticus) (Young 1995), 
Bonneville (Service 2001), and westslope (Bjornn and Mallet 1964, 
McIntyre and Riemand 1995) cutthroat subspecies are known to have a 
migratory life history phase, it is not known if RGCT currently have, 
or once had, a migratory form when there were fluvial (flowing water) 
connections among watersheds.
    Most cutthroat trout are opportunistic feeders, eating both aquatic 
invertebrates and terrestrial insects that fall into the water 
(Sublette et al. 1990). RGCT 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). Many of these fish 
have either been extirpated from streams with RGCT or are greatly 
reduced in number. It is not known if they once were an important 
component of RGCT diet. Other species of cutthroat trout become more 
piscivorous (fish eating) as they mature (Sublette et al. 1990, Moyle 
1976), and cutthroat trout living in lakes will prey heavily on other 
species of fish (Echo 1954). It is possible that native cyprinids 
(i.e., chubs, minnows, and dace) and catastomids may have once been 
important prey items for RGCT.
    Growth of cutthroat trout varies with water temperature and 
availability of food. Slowest growth is seen in high-elevation streams 
where temperatures are cold and productivity is typically low. Most 
populations of RGCT are found in high-elevation streams and under these 
conditions growth may be relatively slow, and time to maturity may take 
longer than is seen in subspecies that inhabit lower elevation streams. 
Based on 471 fish from 3 streams, Cowley (1993) estimated the following 
age/size classes: age 0, 30-64 millimeters (mm), (1.0-2.5 in); age 1, 
65-114 mm (2.5-4.5 in); age 2, 115-149 mm (4.5-5.9 in); age 3, 150-174 
mm (5.9-6.9 in); age 4, 175-205 mm (6.9-8.0 in); and age 5, over 205 mm 
(8.0 in). At Seven Springs Hatchery, eggs hatched in 32 days at 10 
degrees Celcius ( deg.C), 50 degrees Fahrenheit ( deg.F) (NMDGF 2002).
    Typical of trout, RGCT require four types of habitat for survival: 
spawning habitat, nursery or rearing habitat, adult habitat, and 
overwintering habitat. Spawning habitat consists of clean gravel 
(little or no fine sediment present) that ranges between 6 to 40 mm 
(0.24-1.6 in) (NMDGF 2002). Nursery habitat is usually at the stream 
margins where water velocity is low and water temperature is slightly 
warmer. Harig and Fausch (in press) have found that water temperature 
may play a critical role in the life history of the young of the year 
cutthroat. Streams with cold temperatures (less than 7.8 deg.C 
(46 deg.F) mean daily temperature for July) may not have successful 
recruitment or reproduction in most years. The cold temperatures can 
delay spawning and prolong egg incubation. Fry (recently hatched fish) 
emerge later in the summer and may not have sufficient time to grow and 
gain metabolic reserves to be able to overwinter. Overwintering habitat 
in the form of large deep pools that do not freeze is also necessary 
for survival. Lack of large pools may be a limiting factor in headwater 
streams (Harig and Fausch in press).


    It has been estimated that there are 106 populations of RGCT in New 
Mexico (NMDGF 2002) and 161 in Colorado (Alves et al. 2002) in both 
streams and lakes. All of these populations contribute in some way to 
the overall security of the range-wide population. However, many of 
these populations are hybrids, some populations have an extremely low 
number of individuals, and some have been invaded by nonnative 
salmonids that either hybridize or compete with RGCT. These factors can 
make individual RGCT populations more vulnerable to extinction and 
limit the likelihood of their long-term persistence. Conservation 
actions can remove or reduce these threats. Because ecological factors 
affecting persistence vary among populations, we decided to use 
criteria to categorize populations based on vulnerability to threats 
that affect long-term persistence. The populations deemed most likely 
to persist are considered ``core'' populations. Criteria were 
established for purity, population stability, and security from 
invasion by nonnative salmonids. We recognize that our criteria are 
conservative, and that population estimates are not precise. For these 
reasons we also evaluate non-core populations (discussed in the 
conclusion) that do not meet all of the core criteria but are important 
components of the range-wide population.

[[Page 39938]]

Genetic Purity

    For the purposes of this review we considered ``pure'' to mean that 
there was less than 1 percent introgression (genetic mixing) with 
either rainbow or another subspecies of cutthroat trout. Allendorf et 
al. (2001) suggest that conservation efforts should focus on 
maintaining and expanding remaining pure populations, and we have 
decided to follow this guidance for RGCT. To meet our criteria, testing 
for purity had to include either allozymes (forms of an enzyme) or 
nuclear DNA (genetic coding molecule in cell nucleus). We did not 
include populations that were tested only with meristics (counts of 
body parts). Although a meristic evaluation is a good first step to 
determine purity, individuals can look pure and still have a 
significant level of introgression. We also did not include the results 
from mitochondrial DNA (mtDNA). Because mtDNA is passed on only from 
the mother to her offspring, it can only detect hybridization when the 
mother is a rainbow trout or another subspecies of cutthroat trout and 
the father is RGCT; however, it cannot detect hybridization when the 
mother was RGCT and the father was another species. For this reason we 
have not included populations that were only tested with meristics and 
mtDNA or mtDNA only.
    The exclusion of populations with evidence of greater than 1 
percent introgression does not imply that these populations may not be 
important to the species conservation or that they should be eliminated 
from stream systems. They provide recreational opportunities for 
anglers; in some watersheds they may act as a buffer between pure 
populations and downstream areas where nonnatives are present, and in 
some streams hybrids may still contain genes unique to a watershed. 
There is a minimum of 30 pure, remnant populations of RGCT widely 
distributed range-wide. It is likely that the gene pool of the hybrid 
populations is represented in one of the many pure, remnant 
populations. In terms of restoration, only pure populations are used 
for translocation into renovated streams or for use as broodstock in 
hatcheries. For these reasons we view pure populations as particularly 
important to the status of the RGCT.
    We identified a total of 82 populations (remnant and transplants) 
in New Mexico and Colorado that are genetically pure. An additional 13 
populations have been identified as pure by NMDGF and Colorado 
Department of Wildlife (CDOW) based on meristics or a combination of 
meristics and mtDNA. Genetics testing is in progress on 12 populations 
in New Mexico, and 31 more populations are scheduled for testing 
through 2005 (NMDGF 2002). Once additional genetic testing is 
completed, it is likely that several more pure populations will be 

Population Stability

    For the long-term persistence of a population, sufficient 
population size is needed to prevent inbreeding depression (genetic 
defects caused by mating of closely related family members) and 
maintain genetic variation (Franklin 1980). Large populations also have 
been suggested to be less susceptible to both demographic events 
(random changes in the population structure, e.g., uneven male/female 
ratios), and environmental random events (random changes in the fishes' 
surroundings) that can eliminate small populations. The expected time 
to extinction decreases as population size decreases (Rieman et al. 
1993). Habitat size (length of stream) and habitat quality affect the 
potential size of the population: the larger the fragment, the more 
likely the population will be large and able to resist chance 
extinctions (Gilpin and Soul 1986). Smaller stream fragments can have 
less diverse habitats and a lack of refugia (areas where individuals 
can survive through environmentally challenging periods) that can lead 
to greater population fluctuations through time (Rieman and McIntyre 
1995). As long as birth rate equals or exceeds death rate, small 
populations may persist; however, smaller isolated populations may be 
more vulnerable to detrimental effects of genetic change and 
detrimental effects of demographic and environmental change.
    Dr. David Cowley (New Mexico State University) developed a model to 
determine population viability for RGCT in New Mexico (NMDGF 2002). The 
model incorporates habitat size, population size, reproductive success, 
a probability of extinction of less than 10 percent over 100 years, and 
a probability that long-term net effective population size 
(Ne) of 500 is greater than 90 percent. For the purposes of 
this review, we consider elements in the model and work done on other 
populations of salmonids to evaluate the likelihood of long-term 
population persistence. Three factors were considered: population 
number, biomass (weight of fish per unit area), and stream length. Of 
these factors, population number is considered to be the most important 
for viability and has been discussed most often in the literature.
    Franklin (1980) proposed some general rules for effective 
population sizes to maintain a genetically viable population. 
Franklin's ``50/500'' rule is still used as a starting point by which 
to judge the viability of populations. This rule suggests that a short-
term Ne size of 50 will prevent an unacceptable rate of 
inbreeding, and a long-term Ne size of 500 will maintain 
overall genetic variability. The Ne size refers to an ideal 
population of breeding adults produced by the random union of an equal 
number of male and female gametes randomly drawn from the previous 
generation. The population size (N) needed to meet the effective 
population varies according the percent of individuals that are capable 
of breeding, the number of animals that actually breed, sex ratio, and 
other factors. Typically, Ne/N ratios vary from 10 to 33 
percent giving long term population sizes of 2,000 to 5,000 (Thompson 
1991). Population sizes between 2,000 and 5,000 have been suggested as 
appropriate for the long-term persistence of other fish populations 
(Nelson and Soul 1987, Reiman and McIntyre 1993, Hilderbrand and 
Kershner 2000), based on both genetic and demographic consideration.
    For this analysis we consider 2,500 total fish in a population to 
be a number that will ensure long-term persistence (i.e., reduce the 
risks associated with small population size alone). Although larger 
populations are most likely incrementally ``safer,'' in the absence of 
specific work on RGCT, we determined that 2,500 individuals is a 
reasonable number that falls within the range suggested for other 
salmonids. Although there are examples of persistence of much smaller 
populations of RGCT (100-500 individuals), these fish evolved in 
connected systems and we have no assurance at this time that they can 
persist (i.e., survive as a species for 100-500 years). We do not know 
if isolated populations of RGCT can be sustained for long periods (100 
years) in small stream fragments; however, managers have documented the 
persistence of small RGCT populations for at least 30 years 
(Interagency meeting on RGCT, pers. comm. 2002). There are 11 pure 
populations in New Mexico and 10 in Colorado that have more than 500 
and less than 2,500 individuals and 15 populations in both States with 
less than 500 individuals.
    Biomass of fish and stream length are related to population size. 
Both of these factors have been used as alternative methods to judge 
the viability of inland trout populations (Service 1998, Hilderbrand 
and Kershner 2000). In the greenback cutthroat recovery plan, one

[[Page 39939]]

recovery goal is that populations have a biomass of 22 kilograms/
hectare (kg/ha), 20 pounds/acre (ac) (lb/ac) (Service 1998). All the 
RGCT populations with 2,500 fish or more have a biomass greater than 22 
kg/ha (20 lb/ac). The lowest biomass in the populations with 2,500 or 
more individuals is 29 kg/ha (26 lb/ac). Seventeen of 22 populations of 
RGCT with 2,500 fish or more have a biomass of 50 kg/ha (44.6 lb/ac) or 
more. Biomass is not considered a limiting factor in these pure 
    Having sufficient stream length is another factor that can play a 
role in the survival of cutthroat trout populations (Hilderbrand and 
Kershner 2000, Harig and Fausch in press). Fish density is high for 
RGCT populations with over 2,500 individuals, suggesting that the 
stream length of 8 kilometers (km) (4.9 miles (mi)) suggested by 
Hilderbrand and Kershner (2000) is probably sufficient for most of the 
streams. Only one stream reach with a population of more than 2,500 
fish is of a length shorter than is recommended. However, fish density 
is high (0.7 fish/meter, 0.21 fish/foot), and we deduce from this that 
the habitat is of high quality and sufficient to support a strong 
    We identified 22 pure populations with 2,500 or more fish, but 
there may be slightly more or slightly fewer. An inherent problem with 
using population size as a criterion for the status review is that 
populations fluctuate naturally from year to year. Survey sites might 
not represent the entire stream; a limited number of surveys have been 
conducted on each stream (0-4); survey methods vary; survey efficiency 
varies with crew experience and stream conditions (deep water, complex 
habitats such as beaver ponds, and low water conductivity decrease 
electrofishing efficiency); and surveys have not been conducted 
recently on some streams. Around every population estimate are upper 
and lower confidence intervals that may be large or small. It is 
possible that more populations should be included in the pure, secure, 
and stable category because they have slightly less than the 2,500 fish 
criterion employed here. Riley and Fausch (1992) found that two- and 
three-pass removal methods underestimate total abundance because of 
decreasing catchability of fish with each pass (electrofishing a set 
length of stream). Nearly all the survey results are from two- or 
three-pass methods, so it is possible that of the populations that did 
not meet the 2,500 fish criterion, some actually have 2,500 fish or 
more. It is possible that with new survey data the streams in the 
stable group could change with some dropping down below 2,500 fish and 
with others being added. Twelve populations in New Mexico that have 
tested pure have no population information available. It is possible 
that five of these, which are in longer stream segments (8 to 18 km 
[5.0 to 11.2 mi] long), would meet the 2,500 fish criterion.

Population Security

    A population of RGCT is not considered secure if nonnative 
salmonids are present. The presence of rainbow trout in RGCT 
populations is unacceptable because of hybridization. Because brook 
trout (Salvelinus fontinalis) and brown trout (Salmo trutta) are fall 
spawners (RGCT spawn in spring), they do not hybridize with RGCT. 
However, they are competitors for food and space, and there have been 
both historic and recent examples of population extirpation due to 
nonnative introductions. In some limited situations, co-existence of 
RGCT and brook or brown trout may occur, especially in high-gradient or 
high-elevation streams that may favor cutthroat trout. However, not 
enough is known about the competitive interactions between these fish 
to know what factors tip the scale in favor of the nonnatives over 
RGCT. Preliminary evidence from Peterson and Fausch (2001) indicate 
that brook trout have the most impact on young of the year Colorado 
River cutthroat trout. Competitive interactions between RGCT and brook 
or brown trout have not yet been studied. Where nonnatives are present, 
active management must occur to remove them on a regular basis or the 
nonnative trout will gradually replace RGCT. For the purposes of this 
review, the emphasis is on self-sustaining pure populations of RGCT. 
Brook and brown trout are present in several pure populations of RGCT. 
While these populations are less secure than the populations without 
nonnatives, removal of the nonnatives by State agency personnel on a 
regular basis can lead to stable RGCT populations. These populations 
are important to the overall status of the subspecies.
    Inextricably linked to the presence of nonnatives is the presence 
of a barrier. Barriers prevent nonnatives from migrating into habitat 
occupied by RGCT. They also prevent the upstream migration of RGCT, 
limiting gene flow among populations. Until more watersheds with 
connecting tributaries are restored, having secure barriers to prevent 
invasion of nonnatives is essential for protecting existing 
populations. Once large watersheds are restored, upstream barriers 
could be breached to allow for free passage of RGCT upstream and 
downstream. For this status review, populations had to be protected by 
a barrier to be considered secure with no nonnative trout above the 
barrier. We identified 13 populations that are pure (confirmed by 
appropriate genetic testing), have over 2,500 fish, are secured by a 
barrier, and do not coexist with nonnatives (see Table 1 below).

   Table 1.--Streams With Pure, Stable, and Secure Populations of Rio
        Grande Cutthroat Trout, Their Watersheds, and Land Status
            Watershed                   Stream             Ownership
Saguache........................  Cross.............  Rio Grande NF/
San Luis........................  Medano Cr.........  Rio Grande NF/NPS.
Alamosa/Trinchera...............  San Francisco Cr..  private/Rio Grande
                               New Mexico
Canones Cr......................  Canones Cr........  Santa Fe NF.
El Rito Cr......................  El Rito Cr........  Carson NF.
Red River.......................  Bitter Cr.........  Carson NF.
Red River.......................  Columbine Cr......  Carson NF.
Rio Cebolla.....................  Rio Cebolla.......  Santa Fe NF.
Rio Puerco West.................  Rio Puerco (west).  Santa Fe NF.

[[Page 39940]]

San Cristobal...................  San Cristobal.....  Carson NF.
Pecos River.....................  Jacks.............  Santa Fe NF.
Rio Chamita.....................  Powderhouse.......  Carson NF.
Rio Pueblo......................  Policarpio........  Carson NF.
Tested pure with meristics and mtDNA or meristics only..................
Alamosa/Trinchera...............  Cat Cr............  Rio Grande NF.
Alamosa/Trinchera...............  Jaroso Cr.........  private.
Alamosa/Trinchera...............  Torcido...........  private.
Conejos.........................  Osier.............  Rio Grande NF.
Conejos.........................  Cascade Cr........  Rio Grande NF.
NF = National Forest, NPS = National Park Service. Five streams have not
  been tested using allozymes or nuclear DNA, however, it is highly
  likely that they will test pure based on their isolation from
  nonnative trout.

Analysis of Factors Affecting the Populations

    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 lists. A species may be determined to 
be threatened or endangered due to one or more of the five factors 
discussed below.

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

    The historic range of RGCT has been greatly reduced over the last 
150 years. Many populations have been lost or impacted by water 
diversions, dams, habitat degradation, changes in hydrology, 
hybridization with rainbow trout, or competition with brown or brook 
trout. Quantifying the exact magnitude of loss in either number of fish 
or habitat is difficult because there are no baseline data. Stumpff and 
Cooper (1996) estimated the loss in habitat (stream miles) to be about 
91 percent in New Mexico. Harig and Fausch (1998) suggest that native 
cutthroat (greenback and RGCT) have been reduced to less than one 
percent of their historic habitat. Because RGCT are now restricted to 
headwater and first and second order streams that are narrow and small 
compared to larger second, third, and fourth order streams they once 
occupied, the absolute loss of habitat is greater than stream miles 
might indicate and includes the loss of diversity of habitat found in 
larger stream systems. As a consequence of the habitat loss, RGCT 
populations that were once connected are now fragmented.
    The constriction and fragmentation of RGCT habitat most likely 
began gradually about 1350 A.D. and accelerated in the late 1800s. 
Agriculture in the Rio Grande Valley began about 1350 A.D. and water 
diversions for the irrigation of crops started at that time (Crawford 
et al. 1993). Diversion of water from tributaries of the Rio Grande 
probably represents the first interruptions in RGCT habitat. Following 
Spanish colonization in 1598, human influence increased as more land 
was cleared and more acequias (irrigation canals) were built to divert 
water into fields. The greatest contraction in RGCT habitat most likely 
occurred between 1880 and 1973. In 1880, the maximum number of acres in 
the middle Rio Grande Valley were under cultivation, and grazing 
pressure was intense with over 2 million sheep and 200,000 cattle, 
horses, and mules (Crawford et al. 1993). In addition, it is likely 
that RGCT were sought for subsistence during this time. In the early 
1900s, numerous water supply and flood control dams were built in the 
Rio Grande headwaters (Crawford et al. 1993). Rainbow, brook, and brown 
trout were introduced at the turn of the century (Sublette et al. 
1990). The livestock industry grew through the mid-1930s and livestock 
numbers increased far beyond the carrying capacity of the range and had 
a widespread negative impact on riparian systems (Meehan and Platts 
1978). In addition, timber harvest and an associated increase in roads 
led to increased levels of sedimentation in the streams. As a result of 
these multiple impacts, reduction of RGCT habitat occurred range-wide, 
affecting essentially every watershed.
    Habitat fragmentation reduces the total area of habitat available, 
reduces habitat complexity, and isolates the fragments (Saunders et al. 
1991, Rieman and McIntyre 1993, Rieman and McIntyre 1995, Burkey 1995). 
Originally, many watersheds supporting RGCT would have been connected 
creating an interconnected network. 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. Each of these watersheds is now isolated from one 
another, and RGCT are restricted to fragments of streams. Compared to 
the lower elevation, larger order streams, the high-elevation streams 
that RGCT are now restricted to may represent relatively poor habitat. 
Water temperatures are colder, productivity is lower, length of time 
for young-of-the-year development is shorter, and amount of habitat 
available is less. For some isolated populations, fragmentation may 
lead to a negative growth rate and extinction over time (Terborgh and 
Winter 1980).
    Burkey (1995) suggests that fragmentation accelerates extinction, 
especially when dispersal among fragments is not possible, as is the 
case with some RGCT populations. Isolated populations are vulnerable to 
extinction through demographic change (random changes in the population 
structure, e.g., uneven male/female ratios), environmental change 
(random changes in the fishes' surroundings) and catastrophes (e.g., 
fires and massive flooding), loss of genetic heterozygosity (genetic 
diversity) and fixation of rare detrimental alleles (inherited forms of 
a genetic trait), and human disturbance (Burkey 1995). It has been 
suggested that spatial and temporal complexity is needed so that the 
expression of complex life histories (i.e., migratory and sedentary 
forms) can be maintained (Rieman et al. 1993, Dunham et al. 1997, Harig 
and Fausch in press). In

[[Page 39941]]

fragmented habitats, fish are unable to migrate or if they do migrate 
downstream past a barrier, they are lost from the population. It is 
possible that migratory behavior is a hedge against catastrophes. 
Individuals that have migrated away from a stream segment escape death 
during the catastrophic event and are then available to recolonize the 
open habitat once it becomes suitable again (Rieman and McIntyre 1993). 
In streams subject to a variety of natural extreme events (drought, 
fire, flooding) such as the streams in New Mexico, having a variety of 
life histories may have been an evolutionarily advantageous adaptation. 
Currently, fish migrating from isolated streams are lost from the 
population, and, if a population is extirpated, recolonization is not 
possible except through specific management activities such as 
stocking. Over time, this can lead to the loss of migratory behavior as 
the genes responsible for the behavior are non-advantageous and are 
essentially selected against.
    Watershed scale projects have been initiated on both private and 
National Forest lands and are in various phases of implementation. 
Three projects are briefly summarized. A joint project between Vermejo 
Park Ranch and the States of Colorado and New Mexico to restore the 
Costilla Creek watershed is in progress. A Memorandum of Understanding 
was signed by all parties in 2001 and an Environmental Assessment was 
completed. Restoration is scheduled for July 2002. The restoration will 
remove brook trout, brown trout, and introgressed cutthroat trout and 
reintroduce pure RGCT into 4 tributaries and 4 small lakes, totaling 22 
km (13.6 miles) of stream and 9.5 ha (23.5 acres) of lake. A draft 
environmental assessment has been completed on Animas Creek on the 
Ladder Ranch, Sierra County, New Mexico, in cooperation with the Gila 
National Forest. The restoration portion of the project is scheduled to 
occur in October 2002. Approximately 48 km (29.8 miles) of stream will 
be restored. A Watershed Restoration Action Strategy for the Comanche 
Creek watershed has been written, and a work plan has been submitted 
and approved by the New Mexico Environment Department. Six partners 
will work together to improve habitat conditions on Comanche Creek, a 
watershed with over 70 km of streams and pure RGCT in the upper 
tributaries. Recovery of this watershed will be a substantial gain for 
RGCT, especially if the pure populations expand downstream.
    The recent establishment of the Valles Caldera National Preserve 
presents the opportunity to restore the headwaters of the East Fork 
Jemez and San Antonia Rivers with RGCT. With the Santa Fe National 
Forest managing the land downstream of the Valles Caldera, there is the 
opportunity to connect the two river systems together and restore over 
112 km (69.6 miles) of stream. Initial contacts have been made and both 
parties are interested in pursuing this large-scale restoration 
project. The Rio Santa Barbara watershed (Camino Real Ranger District, 
Carson National Forest) is another site with excellent potential to 
reconnect multiple populations (West Fork, Middle Fork, and East Forks 
of Rio Santa Barbara, Jicarita, and Indian Creeks). In 1999, a barrier 
was built on East Fork and the barrier on the Middle Fork Rio Santa 
Barbara was improved. Brown trout were removed from above the barriers 
from 1998 to 2000. While some progress has been made, we note that a 
significant amount of planning and on the ground activities remain to 
be done. We recognize that these projects may not come to fruition, and 
we are not relying on them as part of this status review. However, we 
mentioned them here to recognize that the States and Federal agencies 
are looking for opportunities to conserve the RGCT in areas where it 
historically occurred.
    Habitat fragmentation is a threat that can be alleviated by 
management activities. Currently there are five pure, stable, and 
secure populations that are connected to at least one other tributary. 
Six other large, pure, connected populations exist but nonnatives are 
present. State and Forest Service personnel remove nonnatives from 
these streams during population surveys and as part of ongoing 
management actions.
    The Service determines that fragmentation is not a threat to the 
persistence of these 13 populations now or in the foreseeable future. 
All the 13 pure, stable, and secure populations have over 2,500 fish, 
which provide sufficient numbers to prevent an unacceptable rate of 
inbreeding and to maintain genetic variability in these populations. 
Recognizing this, population sizes between 2,000 and 5,000 have been 
suggested as appropriate for the long-term persistence of other fish 
populations (Nelson and Soul 1987, Reiman and McIntyre 1993, 
Hilderbrand and Kershner 2000), based on both genetic and demographic 
consideration. Additionally, the length of these streams (mean equals 
12.4 km (7.7 mi)) is sufficient to provide diverse habitats to meet all 
the life history requirements of the fish. This statement is supported 
by the high fish density (mean equals 0.5 fish/m (0.15 fish/ft)) 
present in these core streams. Another potential threat from 
fragmentation is related to catastrophic events. However, if a 
catastrophic event (e.g., fire, drought) results in the extirpation of 
one or more of these 13 populations, the States and Federal agencies 
have the capability to replace the population with hatchery fish or 
fish transplanted from another pure population.

Habitat Condition

    Rio Grande cutthroat habitat has been degraded by many activities. 
Impacts have been caused by livestock grazing and timber harvest (with 
associated roads). Mining has impacted specific sites. Livestock 
grazing practices on public land in New Mexico have improved. Changing 
livestock stocking levels and improved management practices have 
occurred and will continue to occur following current management 
direction (James Webb, Rio Grande National Forest, in litt. 1994). 
Restoration of riparian areas and maintaining healthy habitat is a 
priority for the Forest Supervisors and Regional Foresters (Leonard 
Atencio, Santa Fe National Forest, in litt. 2002, Peter Clark, Rio 
Grande National Forest in litt. 2002). Although recovery of these 
habitats can be slow, the continued commitment of managers to restore 
watersheds will continue to improve RGCT habitat over time.
    Timber harvest and associated road building have also led to the 
deterioration of RGCT habitat. However, timber harvest in the National 
Forests has declined appreciably in the last 15 years. As an example, 
in New Mexico, from 1987 to 1990 the amount of timber cut averaged 
146,722 million board feet (MBF). From 1991 to 2001 the average has 
been 35,740 (MBF) (Paul Fink, USDA Forest Service, in litt. 2002). Few 
new roads are built in conjunction with timber harvest as the existing 
infrastructure can be used (Paul Fink, USDA Forest Service, pers. comm. 
2002). Roads are being decommissioned and obliterated on all the 
forests, reducing their contribution to sedimentation of streams. For 
example in Region 3 of the USDA Forest Service, in 1999, 2000, and 
2001, 528, 375, and 332 miles of roads, respectively, were 
decommissioned (Mike Noland, USDA Forest Service, in litt. 2002). Many 
of the current pure, stable, and secure populations occur at elevations 
where timber harvest has not occurred and therefore, have not been 
affected. As management activities proceed to expand populations to 
lower elevations, restoration will continue to improve habitat 
condition in those areas, such as

[[Page 39942]]

is planned on Comanche Creek (discussed above).
    Habitat condition in streams with pure, stable, and secure 
populations was assessed by CDOW, NMDGF, or Forest Service biologists 
depending on which agency was most familiar with a particular stream. 
Condition was rated either as 0, no habitat problems; 0-1 which usually 
indicated that headwater reaches were in good condition and lower 
reaches had problems in discrete areas; 1, some problems identified 
(sedimentation, lack of pools, warm water temperature, heavy metals, 
etc.); and 2, pervasive problems related to RGCT habitat were 
identified. In most instances, sedimentation and problems related to 
livestock grazing were identified as primary sources of habitat 
degradation. While streams that are rated with a ``1'' have some level 
of habitat degradation that probably prevents populations from reaching 
maximum reproductive capability, the degradation is not judged to be a 
threat to the existence of any of the populations. In most instances, 
stream habitat condition was rated between the range of 0 to 1, with 
very few streams rated as 2. Based on the outcome of these assessments 
for each stream, it is the opinion of the agencies responsible that 
habitat problems are typically localized and can be or are being 
addressed through management practices (Interagency meeting on RGCT, 
pers. comm. 2002).
    Based on the information provided to us by agency personnel 
(Interagency meeting on RGCT, pers. comm. 2002), discussed in the 
paragraph above, as well as the information stated above on timber 
harvest and livestock grazing, the Service determines that habitat 
condition is not a threat to the 13 pure, stable, and secure 
populations or to the populations with 500 to 2,500 fish. Although 
habitat condition may prevent maximum reproductive potential in some 
populations, habitat condition is not judged a threat to the existence 
of any of the populations. In addition, as evidenced by the number of 
roads being decommissioned, lower levels of timber harvest and 
associated road building, and changes in livestock management 
practices, sedimentation from these sources is most likely declining. 
Over time we expect RGCT trout habitat to improve.

Fish Barriers

    Barriers are essential to separate RGCT from nonnative salmonids. 
However, to be effective barriers must be checked frequently and be 
maintained. Flood events can either blow a man-made barrier out, change 
the channel morphology permanently, or provide a temporary channel 
around the barrier that fish can use for upstream migration. Older 
gabion barriers (rocks in a wire basket) and culverts appear to be the 
most vulnerable structures. Changes in water velocity (either an 
increase or decrease depending on the situation) can change an 
impassable barrier into one that can be passed. These structures should 
be checked on a regular basis. Regardless of the structure, reaches 
above barriers need to be checked regularly because nonnatives are 
sometimes found upstream of barriers with no evidence of impairment to 
the barrier. This can be caused by an incomplete removal of nonnatives 
during stream restoration or illegal transplantation of nonnative 
trout. The only solution to the latter situation is the education of 
the public and gaining their widespread support for RGCT. Education and 
outreach efforts are discussed below under ``Public sentiment.''
    Both Colorado and New Mexico have conducted barrier inventories 
(see factor D. for further information on past activities). New Mexico 
will assess the status of 8 barriers in 2003, 13 in 2004, and 13 in 
2005 (NMDFG 2002). The Forest Service also assesses barriers as part of 
its stream surveys. With the increase in numbers of Forest Service 
fisheries biologists and technicians that has occurred in the last few 
years, miles of stream inventory have increased. For example, on the 
Carson National Forest a full time Fisheries Biologist and two 
technicians have been added to the staff (Fact sheet received from 
Carson National Forest, in litt. 2002). They completed 50 miles of 
stream surveys in 2001. In 2000, the Santa Fe National Forest hired a 
full time fisheries biologist. In 2001, they employed 2 temporary 
fisheries biologists, 8 fisheries technicians, and 7 interns. In 2001, 
105 miles of stream were surveyed (Ferrel 2001). A similar level of 
staffing is expected for the field season of 2002, and it is 
anticipated that approximately 150 miles of streams will be surveyed 
(James Simino, Santa Fe National Forest, pers. comm. 2002). For these 
reasons, the Service determines that barrier failure is not a threat to 
the 13 pure, stable, and secure populations.

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

    There is no commercial fishing for RGCT. Because of fishing 
regulations in New Mexico and Colorado, recreational angling is not 
considered a threat to the species. Many of the streams with RGCT 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 
RGCT are remote and angling pressure is light (Interagency meeting on 
RGCT, pers. comm. 2002).
    Overutilization for scientific purposes is not considered a threat 
to RGCT. Because of advancements in molecular technology, a small 
clipping from a fin provides sufficient material to perform molecular 
analysis of genetic purity. To test for whirling disease, usually 60 
fish are collected and these fish must be sacrificed. To minimize the 
collection of RGCT, nonnative salmonids are collected preferentially 
over RGCT or sample sites are selected below a barrier that protects a 
population of RGCT. In some situations fewer RGCT will be collected and 
sacrificed for testing.
    Overutilization of a population can occur when it is used 
repeatedly as a source of fish for translocations. Managers must 
carefully assess the status of a population before it is used as a 
source of fish or eggs for broodstock or transplantation of adults to 
other streams. Reducing a population to low levels can make it very 
susceptible to other impacts, such as the introduction of nonnatives as 
has occurred on West Indian Creek in Colorado (Alves et al. 2002). When 
collecting fish for translocation, care must be taken in deciding how 
many, of what age class, and from where fish are taken. The broodstock 
management plan developed by Cowley (1993) for NMDGF addresses these 
issues and provides criteria regarding the selection of founder 
populations. With proper management, depletion of the 13 core 
populations is not a threat.
    The Service determines that overutilization for recreational and 
scientific purposes is not a threat to the 13 pure, stable, and secure 
populations for the reasons stated above. Overutilization for 
commercial or educational reasons has not been identified as a threat.

C. Disease or Predation

    Whirling disease (WD) was first detected in Pennsylvania in 1956, 
being transmitted here from fish brought from Europe (Thompson et al. 
1995). Myxobolus cerebralis is a parasite that penetrates through the 
skin or digestive tract of young fish and migrates to the spinal 
cartilage where it multiplies very rapidly, putting pressure on the 
organ of equilibrium. This causes the fish to swim erratically (whirl), 
and have difficulty feeding and avoiding predators. In severe 
infections, the disease can cause high rates of mortality in young-of-
the-year fish. Water

[[Page 39943]]

temperature, fish species and age, and dose of exposure are critical 
factors influencing whether infection will occur and its severity 
(Hedrick et al. 1999). Fish that survive until the cartilage hardens to 
bone can live a normal life span, but have skeletal deformities. Once a 
fish reaches three to four inches in length, cartilage forms into bone 
and the fish is no longer susceptible to effects from whirling disease. 
Fish can reproduce without passing the parasite to their offspring; 
however, when an infected fish dies, many thousands to millions of the 
parasite spores are released to the water.
    The spores can withstand freezing, desiccation, passage through the 
gut of mallard ducks, and can survive in a stream for many years (El-
Matbouli and Hoffmann 1991). Eventually, the spore must be ingested by 
its alternate host, the common aquatic worm, Tubifex tubifex. After 
about 3.5 months in the gut of the worms, the spores transform into a 
Triactinomyon (TAM). The TAM's leave the worm and attach to the fish or 
they are ingested when the fish eats the worm. Either method can lead 
to infection. It is likely that the parasite will continue to spread to 
more and more streams because the spores are easily transported by 
animals and humans.
    Salmonids native to the United States did not evolve with WD. 
Consequently, most native species have little or no natural resistance. 
Colorado River cutthroat trout and rainbow trout are very susceptible 
to the disease with 85 percent mortality within 4 months of exposure to 
ambient levels of infectivity in the Colorado River (Thompson et al. 
1999). Percent survival of RGCT in this research was less than one 
percent (Thompson et al. 1999). Even though the cutthroat trout had 
lower spore concentrations than did the rainbow trout, they often 
showed more overt signs of the disease and died at a faster rate. Brown 
trout, native to Europe, become infected by M. cerebralis, but rarely 
suffer clinical disease. At the study site on the Colorado River, brown 
trout thrive whereas there has been little recruitment to age 1 of 
rainbow trout since 1992 (Thompson et al. 1999). Yellowstone cutthroat 
trout have also been shown to be very susceptible to WD (Hiner and 
Moffitt 2001).
    Whirling disease was first detected in New Mexico in 1988 in 
rainbow trout imported into private ponds in the Moreno Valley in 
northern New Mexico. The first case of WD in wild trout that could not 
be directly linked to importation or transportation of fish was 
detected in autumn of 1999 in the Pecos River. The Cebolla, San Juan, 
Cimarron, Red and Canones Rivers are also infected. Three of seven 
State hatcheries also tested positive (Seven Springs, Lisboa Springs, 
and Parkview). The M. cerebralis was accidentally introduced in 
Colorado in the 1980s through imported trout from a private hatchery. 
The parasite has been confirmed in three drainages that support RGCT: 
South Fork Rio Grande, Rio Grande, and the Conejos. Eight of Colorado's 
State hatcheries have tested positive for WD.
    In New Mexico all WD positive fish are destroyed. Seven Springs 
fish hatchery has been renovated and is no longer WD positive. There is 
an ongoing program to test more drainages for WD. In Colorado, a policy 
implemented in spring 1995 prevents the stocking of trout from 
hatcheries testing positive into waters where WD has not been found, 
including wilderness areas and streams where native trout may be 
restored, and no WD positive fish are to be stocked in habitats that 
are capable of supporting self-reproducing salmonid populations in 
Colorado after 2003. Trout from positive hatcheries will be stocked 
into waters where the parasite has been found to minimize the risk of 
contaminating other watersheds. Only trout from hatcheries testing 
negative can be stocked into waters where the parasite has not been 
    Although WD is a potential threat to RGCT, high infection rates 
will probably only occur where water temperatures are relatively warm 
and where T. tubifex is abundant. T. tubifex is the secondary host for 
the parasite; when T. tubifex numbers are low, the number of TAMs 
produced will be low, and consequently, the infection rate of RGCT will 
be low. T. tubifiex is a ubiquitous aquatic oligochaete (worm); 
however, it is most abundant in degraded aquatic habitats, particularly 
in areas with high sedimentation, warm water temperatures, and low 
dissolved oxygen. In clear coldwater streams, as is typical of RGCT 
habitat, it is present but seldom abundant. T. tubifex is likely to be 
most abundant in beaver ponds, and populations of RGCT below beaver 
ponds may be at risk (Hiner and Moffitt 2001). In addition, infection 
rate is low at temperatures less than 10 deg.C (50 deg.F) (Thompson et 
al. 1999). At the time when the young fish are most susceptible (spring 
and early summer), the populations in high-elevation streams are 
probably partially protected by low water temperatures.
    One threat to the RGCT is the introduction of WD infected fish into 
waters inhabited by the RGCT. Both States currently have web sites, 
brochures, and information in their fishing regulations regarding WD 
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 WD 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. 
Public education and compliance are two important elements in keeping 
imported fish disease free and not having nonnatives stocked in 
locations where they can enter RGCT streams.
    The Service determines that WD is not a threat to the 13 pure, 
stable, and secure populations because these populations are located in 
high-elevation, headwater streams that typically have cold water and 
low levels of sedimentation limiting T. tubifex populations and 
infection rates from TAMs. Although RGCT is susceptible to infection 
there has not been a documented loss or decline in population number 
due to WD in a wild RGCT population. The States are testing all their 
hatchery fish before stocking, are in the process of documenting which 
streams in their States are WD positive, and are educating the public 
about how to prevent the spread of WD. With these efforts the spread of 
WD should be slowed and any problems in wild populations should be 
quickly detected.

D. The Inadequacy of Existing Regulatory Mechanisms

    The NMDGF and the CDOW have authority and responsibility for the 
management of RGCT on all Federal, State, and private land within their 
respective States. The State agencies' capabilities include the 
regulation of fishing, law enforcement, research, and conservation and 
educational activities relating to RGCT. Policies regarding the 
stocking of nonnative fish (no nonnatives are stocked in RGCT 
populations) and minimization of exposure to WD and other diseases are 
in place in both Colorado and New Mexico. Additionally, New Mexico has 
a broodstock management plan in place.
    New Mexico has an approved management plan currently being 
implemented that will ``facilitate long range cooperative, interagency 
conservation of Rio Grande cutthroat trout.'' From 1999 to 2001, 
population inventory was completed on 18 streams, barrier evaluations 
were completed on 14 streams, and genetic samples were taken from fish 
in 17 streams. The plan has schedules for fiscal years 2003 to 2005 for 
population inventory and monitoring, collection and analysis of genetic 
material, assessing barriers,

[[Page 39944]]

habitat inventory, inventory of unexplored streams, testing for and 
mapping WD, and maintaining a database of all the information. For 
example, 17 streams are scheduled for inventory and monitoring in 2003, 
the genetic purity of 8 populations will be analyzed, and barriers on 8 
streams will be surveyed. A budget for all activities from 2003-2005 is 
also developed.
    Rio Grande cutthroat trout is designated as a species of special 
concern by the State of Colorado. Colorado is both implementing and 
revising a previous management plan. Consistent with their direction to 
monitor populations, protect habitat and populations, and detect 
genetic contamination, 58 populations were monitored and 20 populations 
were analyzed using molecular techniques from 1998 to 2001. From 1999 
to 2001, nonnative trout were removed from 3 streams and one lake, two 
barriers were maintained and one new barrier was installed. An 
inventory of barriers on RGCT streams in Colorado has been developed. 
Approximately 10,000 brochures on RGCT conservation have been 
    A range-wide conservation agreement that will facilitate 
cooperation and coordination among State and Federal agencies and other 
interested parties is in final draft and is expected to be finalized 
before the end of 2002. The agreement's goal is to assure the long-term 
persistence of the subspecies, preserve its genetic integrity, and to 
provide adequate numbers and populations. We applaud the efforts of the 
States to establish this multi-party agreement, and we believe that it 
will serve to better the status of the RGCT overall. We mentioned the 
draft plan in this finding to recognize that the States and Federal 
agencies have taken steps to draft such a plan. However, we are not 
relying on it as part of this status review because it is not finalized 
and would require us to speculate as to the final outcome of the plan.
    The Forest Service, the landowner with the majority of pure RGCT 
populations, is also implementing special management for the RGCT. RGCT 
is a Management Indicator Species (MIS, species which have been 
identified as a representative for a group of species with special 
habitat requirements) on the Santa Fe and Carson National Forests, and 
is proposed as an MIS on the Rio Grande National Forest. All resident 
trout are MISs on the Gila National Forest. Management Indicator 
Species act as proxies for fulfilling the National Forest Management 
Act viability requirement. Habitat objectives are established for 
maintaining the viability of the MIS. The RGCT is also listed on the 
Regional Forester's Sensitive Species List. Sensitive species must 
receive special management emphasis to ensure their viability and to 
preclude trends towards endangerment. Forest Service objectives for 
sensitive species are to develop and implement management practices to 
ensure that the species does not become threatened or endangered, 
maintain viable populations, and develop and implement management 
objectives. The Forest Service also assesses barriers as part of its 
stream surveys (see discussion above in factor A. ``Fish Barriers'' 
    Based on the discussion above, both the States and the National 
Forests have adequate regulatory mechanisms to protect and enhance RGCT 
populations and habitat.

E. Other Natural or Manmade Factors Affecting Its Continued Existence


    Wildfires are a natural disturbance in forested watersheds. 
Historically, fires occurred every 4-5 years (Swetman 1990), and burned 
the understory leaving open stands of older trees. Fire suppression has 
resulted in large increases in fuel loads and understory density. As a 
result, under the proper conditions, wildfires today can spread rapidly 
and burn intensely. In the Southwest, the fire season (May to June) is 
followed by the monsoon season (July to August). Consequently, denuded 
watersheds can be hit by heavy precipitation leading to floods and ash 
flows in streams. Although fish often survive the fire, the ash/slurry 
floods that occur after a fire can eliminate populations of fish from a 
stream (Rinne, 1996, Brown et al. 2001). In addition to ash, fire 
retardant slurry deposited on the fire may wash into streams and kill 
fish (Buhl and Hamilton 2000). Although the return interval for stand 
replacing fire is much greater in the Rocky Mountains (200 + years) 
(Ruediger et al. 2000), a fire of this magnitude could affect fish 
populations in several watersheds as it did in the greater Yellowstone 
ecosystem (Bozek and Young 1994). Because the return interval is 
shorter, fire is a more frequent threat to populations in New Mexico. 
There appears to be an association between severe droughts and large 
fire years (Swetnam and Baisan 1994). Because fire is unpredictable, it 
is hard to assess how great the risk of fire is to individual RGCT 
populations. Because several trout populations in New Mexico have been 
impacted in the last 10 years by fire, it is logical to assume that a 
few isolated RGCT populations could be lost to the effects of fire in 
the foreseeable future.
    Catastrophic fire can also provide the opportunity to reclaim 
streams that were invaded by nonnatives. This situation has occurred on 
the Santa Fe National Forest where fish populations were eliminated 
from the Cow Creek watershed by the Viveash Fire in 2000. Once the 
habitat recovers, approximately 25 stream miles will be repatriated 
with RGCT (Ferrel 2002). The Dome Fire in the Jemez Mountains 
extirpated the fish residing in Capulin Canyon. In partnership with 
Bandalier National Monument, the Santa Fe National Forest is developing 
plans to repatriate RGCT in approximately 10 miles of perennial stream 
(Ferrel 2002). 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, 69,965 ac have been 
treated, improving watershed conditions associated with 62 stream 
miles, and an additional 145,575 ac are planned for treatment to 
improve conditions associated with an additional 79.5 stream miles 
(Ferrel 2002). Over the next 10 to 20 years it is possible that a small 
number of RGCT populations will be lost to fire; however, we do not 
believe that such a loss will affect the long-term persistence of the 
RGCT because the populations are widely distributed and loss of RGCT 
populations that contain nonnatives provides an opportunity to 
reestablish pure RGCT populations.
    The Service cannot determine if fire is a threat to the 13 pure, 
stable, and secure populations. Fire is unpredictable and we have no 
way of determining where or with what intensity a fire may burn because 
so many variables are involved. New Mexico is in the midst of a drought 
and fire can be a threat. Because the populations are spread out across 
the landscape and are not grouped together, the chances of more than 
one population being affected is reduced. As mentioned above, if 
catastrophic fire does occur, it provides an opportunity to reintroduce 
pure RGCT trout into streams that had been dominated by nonnative trout 
and expand the range of RGCT.


    The standard method to collect population information on stream 
trout is electrofishing. In addition, short of complete stream 
renovation, electrofishing is the primary method used to remove brook 
and brown trout

[[Page 39945]]

from RGCT streams. Although there is a continuing need for additional 
data on the existing RGCT populations, it should also be recognized 
that electrofishing could have a negative effect on fish. Kocovsky et 
al. (1997) found that 44 percent of X-rayed fish showed evidence of 
spinal injury in a stream that had been electrofished for 8 years even 
though the fish showed no external sign of injury. It has also been 
shown that in a laboratory setting electroshocking can have a negative 
impact on salmonid eggs (Cho et al. 2001). Nielsen (1998) warns that 
the accumulated effects of electrofishing may be significant especially 
in small populations. Although some fish may be killed or injured by 
electrofishing, it is not known if these impacts affect RGCT 
populations over time. However, managers need to be aware of the 
potential dangers of electrofishing and begin exploring alternative 
methods such as trapping or visual observation as a means by which to 
evaluate populations.
    Currently electrofishing is the primary tool to conduct population 
surveys, and to detect and remove nonnative trout in RGCT streams. It 
is expected that electrofishing in RGCT streams will continue until 
alternative census methods are adopted. Electrofishing will also 
continue to be the primary method for removing nonnatives, as no other 
expedient method exists. Snorkeling surveys are being used by the 
Forest Service as part of their stream inventories. While these 
inventories can detect nonnative adults, it is very difficult to 
distinguish between young trout species.
    The Service determines that electrofishing is not a threat to the 
13 pure, stable, and secure populations. Although individual fish may 
be injured, no research indicates that electrofishing is detrimental to 
populations as a whole. Electrofishing is a necessary tool at this time 
to control nonnative trout and to monitor population size.


    It is likely that future management of RGCT 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). Transmission of disease has been 
discussed (see above discussion on WD) and is a threat that must be 
managed. Maintenance of a ``wild'' broodstock is difficult, but if 
hatchery-reared RGCT are to survive in the wild, care must be taken so 
that broodstock does not become domesticated. Inbreeding can also pose 
a problem (Cowley 1993). Planning is essential in the selection of fish 
used as broodstock. Fish used as broodstock must be genetically pure. 
Streams that are used as sources for broodstock should be rotated so 
that the source population is not depleted and also so that the 
hatchery broodstock is infused with new genes. However, stocks from the 
Rio Grande, Pecos, and Canadian Basins should not be mixed until the 
population genetics of the fish has been clarified. New Mexico has a 
broodstock management plan designed specifically for RGCT that 
addresses these issues (Cowley 1993). Having been implemented in the 
field over the last several years, the feasibility and difficulties of 
various aspects of the plan have been tested. The Plan is currently 
under revision, and it could serve as a range-wide protocol.
    Currently New Mexico has about 16,500 captive RGCT. Although Seven 
Springs Hatchery was to be in full RGCT production by 1998, infection 
by WD, subsequent disinfection and renovation of the hatchery, and 
difficulties in rearing RGCT have delayed full production. However, 
production from Seven Springs should increase over the next few years.
    In Colorado, Haypress Lake contains wild broodstock, and captive 
populations are reared at Poudre Rearing Unit and at the Fishery 
Research Hatchery in Fort Collins. Colorado planted 33,400 RGCT into 6 
waters in 1999, 66,600 into 40 waters in 2000, and 152,700 into 77 
waters in 2001.
    The Service determines that hatchery management is not a threat to 
the 13 pure, stable, and secure populations. Hatchery-reared fish are 
not planted into pure, stable RGCT populations so there is no risk of 
disease transmission into these populations. Hatchery equipment is 
sterilized before being used in the field to prevent disease 
transmission. If the criteria suggested by Cowley (1993) are 
implemented, a wild population would be used for spawning purposes only 
once, insuring that the source population is not depleted or 

Public Sentiment

    Several stream renovation projects are planned in the upcoming 
years. One obstacle that must be recognized is public resistance to the 
use of piscicides such as antimycin. Antimycin is an antibiotic that is 
an effective fish toxicant. It can be neutralized at stations outside 
the treatment area. The public must be educated and support range 
expansion of RGCT, or restoration efforts could be undermined. The 
``Respect the Rio'' program on the Santa Fe National Forest is a 
particularly good example of an outreach effort to educate the public 
and gain support for stream restoration. In 2000, the Santa Fe National 
Forest was awarded a grant to begin this program, and an education 
coordinator was hired in 2002. Nearly 1,000 students and over 200 
adults have heard presentations relating to native fish and respect for 
the land. The Respect the Rio program has three mascots: RGCT, Rio 
Grande chub, and Rio Grande sucker (Ferrel 2002). The Carson and Rio 
Grande National Forests also sponsor activities (e.g., Fish Fiesta) to 
educate and raise public awareness about RGCT. Both State management 
plans include education and outreach elements. Public support is 
essential for the success of future projects, and the States of New 
Mexico and Colorado recognize the importance of education and outreach 
in achieving their conservation goals for the RGCT. For this reason, 
the Service determines that public sentiment is not a threat to the 13 
pure, stable, and secure populations.


    There are 13 confirmed pure populations of RGCT with populations 
over 2,500 fish, that are secured by barriers and do not have nonnative 
competitors. There are an additional five populations in Colorado that 
are considered pure by CDOW based on meristics and/or mtDNA that have 
over 2,500 fish, are protected by a barrier, and have no nonnatives but 
have not yet been tested by allozymes or nuclear DNA (Torcido, Jaroso, 
Osier, Cat, and Cascade Creeks) (Table 1). Once these populations have 
been tested using allozymes or nuclear DNA, it is very likely that some 
or all will be part of the core group of secure populations, bringing 
the total to as many as 18. Biomass values for these populations range 
from 37 to 160 kg/ha (33 to 142 lb/acre). Stream length on Osier and 
Cascade Creeks is less than ideal; however, as in the case of 
Policarpio Creek, New Mexico, fish density in the two streams is high 
(0.89 and 0.5 fish/m (0.27 and 0.15 fish/foot), respectively), 
indicating suitable habitat conditions. In New Mexico, there are 12 
populations that are in the process of being tested and an additional 
12 populations that have tested pure but for which there is inadequate 
information to judge the status of the populations. Five of these 
creeks (Rio Frijoles, Chihuahuenos, Polvadera, Rio de Truchas, and 
Tienditas) are between 8 and 18 km (5.0 and 11.2 miles) long

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and have the potential to be secure populations (see Table 2 below).

Table 2.--Streams That Did Not Meet All The Core Criteria But Are Important Components of Range-Wide RGCT Status
                             and Are Likely To Persist Into The Foreseeable Future.
               Watershed                         Stream name                          Ownership
Tested pure, large populations (5,000-15,000), brook or brown trout present:
Alamosa/Trinchera......................  Sangre de Cristo..........  private.
Alamosa/Trinchera......................  Placer....................  private.
                                                   New Mexico
Rio de las Vacas.......................  Rio de las Vacas..........  Santa Fe NF.
Rio de las Vacas.......................  Rito Caf..................  Santa Fe NF.
Comanche Creek.........................  Comanche Creek............  Carson NF.
Tested pure, no population information, stream length 8-18 km:
                                                   New Mexico
Rio Frijoles...........................  Rio Frijoles..............  Santa Fe NF.
Canones................................  Chihuahuenos..............  Santa Fe NF.
Rio Quemado............................  Rio de Truchas............  Carson NF.
Rio de Fernando de Taos................  Tienditas.................  Carson NF.
Canones................................  SF Polvadera..............  Santa Fe NF.
NF = National Forest. Not shown are the 21 streams with pure populations with between 500-2,500 RGCT (discussed

    Additionally, some large populations of pure RGCT have recently 
been invaded by nonnatives, either because of barrier failure or 
illegal transplantation. In Colorado, low numbers of brook trout have 
been found in Sangre de Cristo Creek (with tributary Wagon Creek); 
however, population size (over 9,000 RGCT), biomass, and stream length 
are excellent. The same situation exists in the Placer Creek watershed 
where there are four linked tributaries (total of over 11,000 RGCT). In 
New Mexico, Rio de las Vacas and its tributaries, Rio de las Perchas 
and Rio Anastacio (total of over 15,000 RGCT); Rito Caf (5,000 RGCT); 
and Comanche Creek (5,000 RGCT) are all strong RGCT populations that 
have either brook trout or brown trout present (Table 2). Brown trout 
were found in Rio de las Vacas in 2001. Electrofishing removal and 
surveys are scheduled for 2002 and the existing barrier will be 
improved by the Forest Service. These populations are important 
components of the range-wide population. Agency personnel are aware of 
the undesirability of nonnatives in RGCT streams and remove nonnatives 
both during the course of regular stream surveys and as on-going 
programs in selected streams.
    In addition, there are 11 pure populations in New Mexico and 10 in 
Colorado (21 total) that have more than 500 and less than 2,500 fish 
and 15 pure populations in both States with less than 500 individuals. 
While these populations may be at greater long-term risk of extinction 
compared to large populations, they continue to persist. In the future 
these populations may be expanded downstream, and they may serve as 
repositories of unique genetic material. As such they also are 
important components of the range-wide population and provide 
additional security for the overall status of the subspecies.
    In the context of the Act, the term ``threatened species'' means 
any species 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 endangered species 
under the Act are the threats that currently confront the species and 
the likelihood that the species will persist in the ``foreseeable 
future.'' Specific threats discussed in detail above in our five factor 
analysis include nonnative salmonids that either hybridize or compete 
with RGCT, habitat fragmentation, livestock grazing, timber harvest, 
overutilization, disease (e.g., whirling disease), inadequacy of 
existing regulatory mechanisms, fire, electrofishing, and opposition to 
the use of fish poisons (e.g., piscicides). We have determined that the 
13 core populations are not threatened by any of the identified threats 
alone or in combination.
    Our finding is also based upon the other large populations of RGCT 
identified in Tables 1 and 2, as well as the 21 other populations 
discussed above. We find that these populations are likely to persist 
into the future because of the large numbers of individuals within 
these populations and the threats are adequately addressed by the 
ongoing management actions of the States and Federal agencies to remove 
nonnatives (brook and brown trout), test for genetic purity, conduct 
stream surveys, maintain barriers, conduct public education and 
outreach, and test for WD.
    At different times in discussing the ongoing management actions by 
the State or Federal government we have included a discussion of 
actions that are projected to occur over the next few years. We 
described the future conservation actions that agencies indicate they 
will be undertaking, but we have not relied on these future actions for 
purposes of determining the current status of the species or the 
adequacy of current management actions to alleviate threats to the 

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    After reviewing the best scientific and commercial information 
available (1998 status review, available literature, information 
supplied to us by State and Federal agencies, and other unpublished 
documents and maps), for all of the reasons discussed herein, we find 
that the RGCT is not endangered and is not likely to become endangered 
within the foreseeable future throughout all or a significant portion 
of its range and that listing as threatened or endangered is not 
warranted at this time.

References Cited

    A complete list of all references cited in this notice is available 
from the New Mexico Ecological Services Field Office (see ADDRESSES 


    The authority for this action is the Endangered Species Act (16 
U.S.C. 1531 et seq.).

    Dated: June 3, 2002.
Steve Williams,
Director, Fish and Wildlife Service.
[FR Doc. 02-14569 Filed 6-10-02; 8:45 am]