Endangered and Threatened Wildlife and Plants; Withdrawal of the Proposed Rule To List the Cow Head Tui Chub (Gila bicolor vaccaceps, 59700-59711 [E6-16544]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 71, Number 196 (Wednesday, October 11, 2006)]
[Proposed Rules]
[Pages 59700-59711]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E6-16544]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AV01


Endangered and Threatened Wildlife and Plants; Withdrawal of the 
Proposed Rule To List the Cow Head Tui Chub (Gila bicolor vaccaceps) as 
Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; withdrawal.

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SUMMARY: We, the Fish and Wildlife Service (Service), have determined 
that the proposed listing of the Cow Head tui chub (Gila bicolor 
vaccaceps) as an endangered species under the Endangered Species Act of 
1973, as amended (Act), is not warranted, and we therefore withdraw our 
March 30, 1998, proposed rule (63 FR 15152-15158). We have made this 
determination because the threats to the species identified in the 
March 30, 1998, proposed rule are not significant, and currently 
available data do not indicate that the threats to the species, as 
analyzed under the five listing factors described in section 4(a)(1) of 
the Act, are likely to endanger the species in the foreseeable future 
throughout all or a significant portion of its range.

ADDRESSES: Supporting documentation for this action is available for 
public inspection, by appointment, during normal business hours at the 
U.S. Fish and Wildlife Service, Klamath Falls Fish and Wildlife Office, 
6610 Washburn Way, Klamath Falls, OR 97603.

FOR FURTHER INFORMATION CONTACT: Curt Mullis, Field Supervisor, at the 
above address (telephone, 541-885-8481, or facsimile, 541-885-7837).

SUPPLEMENTARY INFORMATION:

Background

    The Cow Head tui chub, Gila (Siphateles) bicolor vaccaceps, is a 
small fish in the minnow family Cyprinidae. It was first recognized as 
a distinct subspecies in 1939, and was later named and formally 
described in 1980 (Bills and Bond 1980, pp. 320-322). Although it was 
referred to as the Cowhead Lake tui chub in the March 30, 1998, 
proposed listing (63 FR 15152), we now conform to the accepted 
geographical spelling of Cow Head as two words and use the shorter 
name, Cow Head tui chub, for reasons discussed in Reid (2006b, pp. 1-
6). It is distinguished from other tui chubs primarily by the number 
and form of its gill rakers (bony projections in the gills), as well as 
other characteristics, such as fin and scale counts, and the shape of 
its fins and head (Bills and Bond 1980, pp. 320-322). Like other tui 
chubs, its coloration is generally silver, except for a dark lateral 
stripe and dark speckles scattered on the cheek, operculum (area behind 
the eye), and lower body.
    The known range of the Cow Head tui chub is limited to the Cow Head 
Basin in extreme northeastern California and northwestern Nevada (Reid 
2006a, pp. 15-19). The Cow Head Basin is relatively small (10,400 
hectares (ha); 25,700 acres) and drains north into the Warner Basin of 
Oregon through Cow Head Slough. Historically, the basin contained a 
shallow, marshy lake when sufficient water was available. Cow Head Lake 
was altered in the 1930s, following the extended drought of the 1920-
30s, to allow drainage of the lake in the spring and to facilitate 
agricultural uses of the lakebed.
    Populations of Cow Head tui chub occupy all principal low gradient 
streams in the basin (Cow Head Slough and Barrel, West Barrel and Keno 
creeks) and a relatively large population still exists on the lakebed, 
where it is restricted to permanent water in drainage channels when the 
lake is dry (Scoppettone and Rissler 2006, pp. 108-109). Stream 
populations of Cow Head tui chub annually expand throughout most of the 
low gradient stream habitat in the basin during wet periods and 
contract as the summer progresses and streams dry up. Connectivity 
between stream populations of Cow Head tui chub is generally 
unobstructed during springtime flows, but during summer and fall, all 
populations are restricted to

[[Page 59701]]

isolated perennial pools (Reid 2006a, p.19).
    Landownership in the Cow Head Basin is both private and Federal 
(U.S. Bureau of Land Management (BLM)). However, most perennial habitat 
of the chub is on private land (Reid 2006a, p. 10-11).
    Cow Head tui chubs generally occupy pool areas in streams and open 
water channels having dense aquatic vegetation (Homuth 2000, p. 6; 
Moyle 2002, p. 124; Reid 2006a, p. 20). They grow about 50 millimeters 
(mm) (2 inches (in)) fork length (tip of nose to the fork in tail) 
during the first year and reach an average of 100 mm (4 in) at about 5 
years of age, with larger individuals uncommon (Scoppettone and Rissler 
2003, p. 5; Scoppettone and Rissler 2006, p. 110). The maximum recorded 
size for Cow Head tui chubs is 235 mm (9 in) (Scoppettone and Rissler 
2006, p. 111).
    Although there is no specific information on the reproductive 
behavior of the Cow Head tui chub, spawning by most tui chubs usually 
takes place from late April to late June, beginning in their second to 
fourth year (Moyle 2002, pp. 124-125). Fecundity is relatively high, 
and a female of 100 mm (4 in) produces about 4,000 eggs over a series 
of spawning events. Tui chubs typically spawn in groups, with several 
males attending each female. Eggs adhere to plants, or the bottom, and 
hatch in about 3-6 days (Moyle 2002, pp. 124-125).
    Tui chubs in general evolved in the arid Great Basin where water 
bodies experience wide fluctuations in water conditions, and therefore 
they are highly tolerant of high alkalinity, high turbidity, and high 
temperatures (Moyle 2002, pp. 124-125). They also appear to tolerate 
relatively low levels of dissolved oxygen (Castleberry and Cech 1986, 
pp. 149-150; Moyle 2002, p. 124). While there have been no long-term 
diurnal studies of water quality in the Cow Head Basin, short-term 
surveys and measurements associated with distributional surveys in Cow 
Head streams and channels indicate that most water quality parameters 
are generally well within the documented tolerances of tui chubs, with 
the exception of localized low dissolved oxygen conditions near the 
bottom of desiccating pools and canals (Richey 1999, pp. 20-25; Homuth 
2000, p. 6; Scoppettone and Rissler 2003, p. 6). There are no records 
of large fish die-offs caused by water quality in permanent pools or 
canals associated with the Basin, again indicating that water quality 
parameters are well within limits tolerated by tui chubs. Fish trapped 
in seasonal pools die as the season progresses and the pools dry up 
(Homuth 2000, p. 8), but this is not due to water quality.

Previous Federal Actions

    On December 30, 1982, the Service published a revised notice of 
review for vertebrate wildlife in the Federal Register (47 FR 58454) 
designating the Cow Head tui chub as a category 2 candidate. At that 
time, the Service defined category 2 candidates as taxa for which 
information in the Service's possession indicated that a proposed 
listing rule was possibly appropriate, but for which sufficient data on 
biological vulnerability and threats were not available to support a 
proposed rule (45 FR 82481, December 15, 1980). The Service 
reclassified the Cow Head tui chub as a category 1 candidate in the 
November 21, 1991, notice of review (56 FR 58804). Category 1 candidate 
species were defined as ``taxa for which the Service presently has 
sufficient information on hand to support the biological 
appropriateness of their being listed as endangered or threatened'' (45 
FR 82480, December 15, 1980). In the Candidate Notice of Review 
published on February 28, 1996 (61 FR 7595), the Service announced a 
revised list of candidate plant and animal taxa based on a single 
category for candidates that closely matched the previous definition of 
category 1 candidates. Specifically, the 1996 notice adopted a single 
category of candidates, defined as: ``those species for which the 
Service has on file sufficient information on biological vulnerability 
and threat(s) to support issuance of a proposed rule to list but 
issuance of the proposed rule is precluded'' (61 FR 7597). As a former 
category 1 candidate taxon, the Cow Head tui chub was included as a 
candidate in the February 28, 1996 (61 FR 7596), and September 19, 1997 
(62 FR 49398), notices of review.
    On March 30, 1998, the Service published in the Federal Register a 
proposed rule to list the Cow Head tui chub as endangered (63 FR 
15152). The Cow Head tui chub was proposed for listing based primarily 
on concerns about the apparent present and threatened destruction, 
modification, and curtailment of its habitat and range (particularly as 
related to dewatering of Cow Head Lake and livestock grazing), as well 
as other natural or manmade factors affecting its continued existence 
(particularly the introduction of pesticides into the drainage as a 
result of pest control activity, and vulnerability to random naturally 
occurring events that can pose risks associated to small, restricted 
populations) (63 FR 15152-15155). The proposed rule also stated that 
introduction of nonnative fish, game fish, or other nonnative tui chubs 
could harm the Cow Head Lake tui chub through increased competition, 
predation, and hybridization (63 FR 15154). The proposed rule had a 60-
day public comment period, until May 29, 1998. On June 17, 1998, we 
reopened the comment period for an additional 65 days at the request of 
private citizens and organizations (63 FR 33033). The second comment 
period closed on August 3, 1998. On February 2, 2000, we opened a third 
comment period at the request of signatories of the conservation 
agreement (described below), to allow the Service to consider 
conservation measures in the conservation agreement; this comment 
period closed on February 16, 2000 (65 FR 4940).

Conservation Agreement

    On October 22, 1999, stakeholders signed a conservation agreement 
(CA), including a conservation strategy, with the stated purpose of 
ensuring the long-term survival of the Cow Head tui chub (Service 1999, 
p. 2). Signatories included private landowners of Cow Head Lake, Cow 
Head Slough, and the California reach of Barrel Creek (four owners, all 
CA signatories); principal permittees on BLM lands within the drainage; 
California and Modoc County Cattlemen's Associations; the California 
Farm Bureau Federation; the BLM (Surprise Field Office); and California 
Department of Fish and Game (CDFG). The two owners on West Barrel Creek 
and the single owner for perennial reaches of Barrel and Keno creeks 
(Nevada) were not original signatories to the CA, as chub populations 
in those areas were unknown at the time; however, these landowners have 
been supportive by providing access to meet the goals and objectives of 
the conservation strategy.
    The stated purpose of the conservation strategy is to identify 
specific procedures and strategies required for the long-term survival 
of the Cow Head tui chub. The strategy has two main objectives: Phase 
one--develop baseline data; and Phase two--use the baseline data to 
determine the most feasible conservation actions to implement the goals 
of the conservation strategy. Phase one included studies intended to 
increase our understanding of the species and its habitat. Most of the 
proposed actions in Phase one have been addressed or are part of 
ongoing projects.
    Phase two builds upon the information developed in Phase one, or

[[Page 59702]]

by any future studies, to adaptively implement conservation and 
management actions to meet the goals of the conservation strategy. The 
general goals of actions implemented in Phase two (and their completion 
status) are: (1) To establish, or confirm the current existence of, 
additional populations (completed); (2) to create more stable habitat 
for those populations (in progress); (3) to provide greater assurance 
of stability for the Cow Head tui chub population upstream of the pump 
in the lakebed channels (ongoing); (4) to create, to the extent 
feasible, additional stable habitat in the area of historic Cow Head 
Lake upstream of the pump (under review); and (5) to monitor, as 
appropriate, the status of Cow Head tui chub populations and 
effectiveness of conservation actions (ongoing).
    By signing the October 22, 1999, CA, the Service and other 
stakeholders in the Cow Head Lake watershed committed to actions and 
goals intended to ensure the long-term survival of the Cow Head tui 
chub by balancing current practices in the watershed with the long-term 
needs of the subspecies. As previously stated, we opened a third 
comment period on the proposed rule on February 2, 2000, by request of 
signatories to the CA, so that the Service could also consider the 
conservation measures of the CA when making a final determination (65 
FR 4940). The third comment period closed on February 16, 2000.

Summary of Public Comments

    During the comment period for the March 30, 1998, proposed rule, we 
received 13 responses from local government, local organizations, and 
private individuals. Of those responses, none provided new information 
pertinent to the proposed listing. Six responses expressed views 
against the listing, one implied general support of the listing, and 
six were requests for a 60-day extension. There were no requests for a 
public hearing.
    On June 17, 1998, the Service reopened the comment period on the 
proposed rule in response to requests from private organizations and 
private citizens (63 FR 33033). During the second comment period, only 
one comment letter was received. It provided additional information on 
historical conditions, past and current management, and trends in 
riparian conditions. The commenter did not state a position relative to 
the appropriateness of the proposed listing.
    On February 2, 2000, we reopened the comment period on the proposed 
rule to allow consideration of the conservation agreement signed on 
October 22, 1999, and to solicit additional information on the biology, 
distribution, and status of the Cow Head tui chub (65 FR 4940). The 
reopening of comment period was in response to requests from 
signatories of the conservation agreement. During the third comment 
period, the Service received five responses from State and local 
governments and private individuals. Four responses were against the 
proposed listing, and one was in support. No new information pertinent 
to the proposed listing was obtained.
    (1) Comment: One commenter felt that the Service could not 
demonstrate that this action has the purpose of interstate commerce, 
and thus the Service did not have the authority to apply the protection 
of the Act.
    Our Response: We disagree with this comment. The Service has the 
authority to protect all endangered species, including intrastate 
species or those with no direct commercial value in interstate 
commerce.
    (2) Comment: One commenter stated that there is a deficiency in the 
data, asserting the Service lacks information about the historical 
range of the fish and evidence of endangerment across the species 
range, and thus cannot move forward with listing the species under the 
Act.
    Our Response: In the March 30, 1998, proposed rule (63 FR 15152), 
the present or threatened destruction, modification, or curtailment of 
its habitat and range was a factor considered to threaten the Cow Head 
tui chub. At that time, we stated that the diversion of water from Cow 
Head Lake had eliminated approximately 98 percent of the chub's 
historical range and that the dewatering was a threat to the species. 
Based on the information available, the chub was thought to be 
restricted to a very small portion of its historic range, occurring 
only in various pools along the southern portion of Cow Head Slough, 
and in the drainage channels on the bed of Cow Head Lake, for a total 
range of approximately 5.4 km (3.4 mi), with no additional populations 
known (for additional information see Factor A below). Since the 
proposed rule was published, the Service has gathered much more 
information about the species' range and habitat conditions (including 
information from Reid 2006a, 2006b). Current information, based on more 
complete basin-wide surveys, demonstrates that the Cow Head tui chub is 
more widely distributed than previously thought and maintains 
populations throughout all of its historical range, including in all 
streams and lakebed channels that would have offered suitable habitat 
in the past. We therefore recognize that the perceived reduction of 
historical range, and the related concern of dewatering that was 
believed to be the cause of the reduction in the range, was a function 
of incomplete information and that current information demonstrates 
that reduction of the historical range has not occurred and is not a 
threat to the Cow Head tui chub. Recognizing that this and other 
threats we identified in the March 30, 1998, proposed rule (63 FR 
15152) either (1) do not exist or (2) have been eliminated or otherwise 
ameliorated, we have determined that the Cow Head tui chub does not 
meet the Act's definition of either a threatened or an endangered 
species. Consequently, we are withdrawing the proposal to list the 
species. For further information, please see the Summary of Factors 
Affecting the Species section below.
    (3) Comment: One commenter stated that Cow Head tui chub could live 
in highly eutrophic water and that this was not a threat as the Service 
had indicated in the March 30, 1998, proposed rule.
    Our Response: Eutrophic water conditions were not one of the 
substantial threats we identified in our proposed rule; however, we 
noted this condition as a subject of potential concern. As described in 
the background section of this notice, tui chubs in general evolved in 
the arid Great Basin and are highly tolerant of high alkalinity, high 
turbidity, and high temperatures (Moyle 2002, pp. 124-125). They also 
appear to tolerate relatively low dissolved oxygen levels in water 
(Castleberry and Cech 1986, pp. 149-150; Moyle 2002, p. 124). While 
there have been no long-term diurnal studies of water quality in the 
Cow Head Basin, short-term surveys and measurements associated with 
distributional surveys in the various Cow Head streams and channels 
indicate that most water quality parameters are generally well within 
the tolerances of tui chubs. Additionally, there are no records of 
large fish die-offs caused by water quality in the permanent pools or 
the canals associated with the Basin, again indicating that water 
quality parameters are well within limits tolerated by the chubs. Fish 
trapped in seasonal pools certainly die as the season progresses and 
the pools dry up (Homuth 2000, p. 8). We recognize that most water 
quality parameters collected within the range of the Cow Head tui chub 
since the 1998 proposed rule, with the exception of localized low 
dissolved oxygen conditions near the bottom of desiccating pools and 
canals, are

[[Page 59703]]

generally well within the tolerances of tui chubs (Richey 1999, pp. 20-
25; Homuth 2000, p. 6; Scoppettone and Rissler 2003, p. 6), and poor 
water quality is not a threat to the Cow Head tui chub. Considering 
that this and the other threats we identified in the March 30, 1998, 
proposed rule do not exist, or have been eliminated or otherwise 
ameliorated, we are withdrawing the proposal to list the species. For 
further information, please see the Summary of Factors Affecting the 
Species section below.
    (4) Comment: One commenter stated the Service had poorly 
articulated the threat from native wildlife, and the threat from future 
introductions of nonnative fish and disease was unlikely.
    Our Response: In the March 30, 1998, proposed rule (63 FR 15152), 
the introductions of a catastrophic disease or nonnative predatory fish 
were both recognized as potentially harmful to Cow Head tui chub, 
particularly due to the small estimated population size and confined 
known range of the chub at that time. However, this factor was not 
considered a principal threat to the chub. Since 1998, the Service has 
gathered additional information about the extent of predation and the 
likelihood of nonnative introduction and disease (Reid 2006a, p. 28; 
also see Factor C discussion, below). The Service notes that no disease 
or predator currently threatens the Cow Head tui chub and that the 
introduction and establishment of a disease or nonnative fish predator 
into the Cow Head Basin is unlikely. Were introduction and 
establishment of a disease or nonnative fish predator into the Cow Head 
Basin to occur, is not likely to threaten the chub with extinction, as 
explained below in our discussion of Factor C. We recognize that the 
potential threats to the tui chub from disease and introductions of 
nonnative predatory fish are both unlikely and minor. Considering that 
these and other threats we identified in the March 30, 1998, proposed 
rule (63 FR 15152) either (1) do not exist or (2) have been eliminated 
or otherwise ameliorated, we are withdrawing the proposal to list the 
species. For further information, please see the Summary of Factors 
Affecting the Species section below.
    (5) Comment: One commenter stated there were no current threats to 
the species; therefore the Service was incorrect in its determination 
that inadequacy of existing regulations to reduce risk was a threat to 
the species.
    Our Response: In the March 30, 1998, proposed rule, the Service 
found that there were no existing regulations to deal with the threats 
to the species described in the proposed rule (63 FR 15152). Since 
1998, information developed about potential threats leads the Service 
to conclude that there are currently no recognized threats to the 
continued existence of the Cow Head tui chub; therefore additional 
regulatory mechanisms are unnecessary. Also, we now know that the Cow 
Head tui chub maintains populations throughout all of its historical 
range, and this has occurred in the context of the existing regulatory 
mechanisms. Therefore, we recognize that inadequacy of existing 
regulatory mechanisms is not a threat to the Cow Head tui chub. 
Considering that this and other threats we identified in the March 30, 
1998, proposed rule (63 FR 15152) either (1) do not exist or (2) have 
been eliminated or otherwise ameliorated, we are withdrawing the 
proposal to list the species. More information on the topic of adequacy 
of existing regulatory mechanisms can be found in Factor D discussion, 
below.
    (6) Comment: One commenter stated that the Service offered no proof 
that pesticide programs were a threat to the species.
    Our Response: The concern over impacts of pesticides was based on 
the assumption that nearby agricultural activities used pesticides and 
that the Cow Head tui chub population had been reduced to a single, 
small population, with an extremely restricted range and no additional 
populations available for recolonization in the event of a localized 
extinction (63 FR 15152). Using new information gathered since 1998, 
the Service has found that the population is not as small as previously 
thought. (See Factor D discussion below.) Agricultural activities and 
land management in the Cow Head Basin are limited to hay production and 
grazing (Reid 2006a, p. 10). The only substantial use of pesticides is 
in the U.S. Department of Agriculture's grasshopper control program, 
which occurs only during occasional years when grasshopper outbreaks 
occur, and then it focuses on localized upland areas surrounding the 
lakebed that are used by grasshoppers for egg laying. Pesticides are 
not applied to aquatic habitat, and in the event of an accidental spill 
or application, the adverse effect would be localized, particularly 
because application typically occurs in late summer when flow is low 
and pool habitats are not connected (Reid 2006a p. 19; see also Factor 
E discussion below). We recognize that pesticide use is not a 
significant threat to the Cow Head tui chub. Considering that this and 
other threats we identified in the March 30, 1998, proposed rule (63 FR 
15152) either (1) do not exist or (2) have been eliminated or otherwise 
ameliorated, we are withdrawing the proposal to list the species. For 
further information, please see the Summary of Factors Affecting the 
Species section below.
    (7) Comment: One commenter stated that the Service had no proof 
that the risks associated with small and restricted fish populations 
was a threat.
    Our Response: The vulnerabilities identified in the March 30, 1998, 
proposed rule (63 FR 15152) (possible excessively high death or low 
birth rates, deleterious effects of genetic drift and inbreeding, and 
sensitivity to localized stochastic events) were based on the 
assumption that the Cow Head tui chub had been reduced to a single, 
small population, with an extremely restricted range and no additional 
populations were available for recolonization in the event of a 
localized extinction. Using information gathered since 1998, we have 
found that the chub is not as reduced as previously thought. (See 
Factor D discussion, below.) Also, a recent genetic study of tui chubs 
found that the genetic diversity in the Cow Head tui chub is similar to 
other stream-resident chub populations, and there is no indication of 
genetic threats (Chen 2006, p. 46-48). The fact that the Cow Head tui 
chub is restricted in population size and distribution does not by 
itself pose a significant risk to the species. Considering that this 
and other threats we identified in the March 30, 1998, proposed rule 
(63 FR 15152 either (1) do not exist or (2) have been eliminated or 
otherwise ameliorated, we are withdrawing the proposal to list the 
species. For further information, please see the Summary of Factors 
Affecting the Species section below.
    (8) Comment: Six commenters requested a 60-day extension of the 
comment period.
    Our Response: In response to these requests, the Service reopened 
the comment period for 65 days.
    (9) Comment: Two commenters stated that humans have influenced 
water movement in the Cow Head tui chub's range and this has benefited 
the chub by enhancing or protecting aquatic habitat.
    Our Response: We agree with the commenters that humans can provide 
benefits to aquatic species in a highly manipulated environment because 
of our desire to create permanent water sources. In the Cow Head basin, 
some areas of perennial habitat are maintained by water management 
structures and these structures can decrease the likelihood of 
nonnative fish getting into the area. (See discussions of Factors C and 
E, below.)

[[Page 59704]]

Since 1998, we have investigated the effects of historical changes in 
water-flow patterns on the Cow Head tui chub's status. As a result of 
interest in the conservation agreement, we were able to work with local 
residents to develop a better understanding of water flow and 
management in the area, and have considered that information in our 
assessment of potential impacts to the chub. (See discussion of habitat 
under Factor A, below.) We no longer believe that water management is a 
current or potential threat. Considering that this and other threats we 
identified in the March 30, 1998, proposed rule (63 FR 15152) either 
(1) do not exist or (2) have been eliminated or otherwise ameliorated, 
we are withdrawing the proposal to list the species. For further 
information, please see the Summary of Factors Affecting the Species 
section below.
    (10) Comment: One commenter felt that the proposed listing was an 
attempt to take away private landowner's rights.
    Our Response: The commenter's concerns regarding the effects of 
listing on private property rights is no longer germane because we are 
withdrawing our 1998 proposal to list the Cow Head tui chub (63 FR 
15152). However, the listing of a species under the Act, in and of 
itself, does not affect private lands and does not effect a taking of 
private property by the Federal government. Only if the landowner 
engages in an activity that is likely to take a listed fish or wildlife 
species, or an activity that requires Federal authorization or funding 
and may affect a listed species, do the Act's regulatory restrictions 
come into play. In those situations, the Act provides regulatory 
mechanisms under Sections 7 and 10 to enable such activities to proceed 
consistent with protection of the listed species.
    (11) Comment: One commenter stated that the Cow Head tui chub 
should not be listed because the conservation agreement was in place.
    Our Response: We believe conservation agreements are important 
conservation tools, and this particular agreement was especially 
crucial for identifying information gaps and forming a basis for 
collaboration. By signing the conservation agreement, the Service and 
other stakeholders in the Cow Head Lake watershed committed to actions 
and goals intended to ensure the long-term survival of the chub by 
balancing current practices in the watershed with the long-term needs 
of the subspecies. Although we believe the Cow Head tui chub 
conservation agreement is important, listing decisions are made based 
on a thorough analysis of all substantial and foreseeable threats. 
Based on an analysis of all the factors, and the new information 
collected with the help of the conservation agreement, we no longer 
believe the Cow Head tui chub is in danger of extinction throughout all 
or a significant portion of its range or likely to become so in the 
foreseeable future; therefore we are withdrawing the March 30, 1998 
proposal to list the chub (63 FR 15152).
    (12) Comment: California Department of Fish and Game questioned 
whether the modification to landowner agreements would impact the 
implementation of the conservation agreement.
    Our Response: In a recent peer review of Reid (2006a), Randal C. 
Benthin, Senior Fishery Biologist at the California Department of Fish 
and Game (CDFG), wrote a letter to us confirming that the landowners 
have been working with management agencies to implement the 
conservation agreement, and he praised their commitment. We discussed 
this comment with Mr. Benthin, in a September 22, 2006 phone call, and 
he said the issue was satisfactorily addressed in the final 
conservation agreement. He further stated that CDFG had no further 
concerns.
    (13) Comment: One commenter stated that the listing should be 
delayed so that additional populations could be established. The 
commenter felt that if the species were listed, the resulting section 7 
consultation process would delay the establishment of additional 
populations.
    Our Response: We agree with the commenter that multiple populations 
are important for species conservation. In the case of the Cow Head tui 
chub at the time of the original listing proposal, we believed that the 
number of populations was quite small (63 FR 15152). Since the March 
30, 1998, proposed rule was published, we determined that the number of 
populations is larger than originally thought. New surveys show the Cow 
Head tui chub maintains populations throughout all of its historical 
range in all streams and lakebed channels that would have offered 
suitable habitat in the past (Reid 2006a, p. 18). Therefore the chub is 
more widely distributed than previously thought. (See Factor A 
discussion, below.) We now recognize that the number of populations and 
relatively narrow range of the species are not threats to the Cow Head 
tui chub. Considering that this and other threats we identified in the 
March 30, 1998, proposed rule (63 FR 15152) either (1) do not exist or 
(2) have been eliminated or otherwise ameliorated, we are withdrawing 
the proposal to list the species. For further information, please see 
the Summary of Factors Affecting the Species section below.
    Regarding the comment that listing the species and any resulting 
section 7 consultations would delay the establishment of additional 
populations, because we are withdrawing the proposal to list the Cow 
Head tui chub, this comment is no longer germane. Nevertheless, even if 
the species were listed, section 7 consultation would not have hampered 
efforts to establish additional populations. Section 7 consultation is 
a valuable tool to minimize adverse effects of Federal actions to 
listed species and, as such, provides benefits to species.
    (14) Comment: One commenter offered several specific goals for 
conservation actions for the species, including establishment of 
additional populations, water management certainty, and protection of 
habitat from over-grazing.
    Our Response: We agree with the commenter that multiple populations 
and protection of habitat from threats are key to species conservation. 
In the case of the Cow Head tui chub, at the time of the original 
proposal, we believed that the number of populations was quite small 
and that there were threats to the quantity and quality of habitat (63 
FR 15152). Since that time, we have focused on addressing these and 
other potential threats and obtaining additional information from 
various sources to clarify the status of the species (e.g., Reid 
2006a). As a result, we have determined that the number of populations 
is larger than originally thought.
    We also looked carefully into the role that current and future 
water availability could have on the conservation of the species. As 
described in more detail under the discussions of Factors A and E 
below, the Cow Head tui chub evolved in a low-precipitation region and 
has survived numerous droughts including a severe 16-year drought early 
in the 20th century. We have also found that current water management 
is compatible with the conservation needs of the species and that there 
is a lack of evidence to suggest water management will substantially 
change in the foreseeable future.
    Furthermore, we have reached a similar conclusion regarding grazing 
management. As described under the discussion of Factor A below, the 
chub has coexisted with the current grazing management for decades, and 
we have no information that leads us to believe grazing management will 
substantially change in a manner that would

[[Page 59705]]

adversely affect the species in the foreseeable future. We now 
recognize that water availability, water management, and grazing do not 
pose threats to the Cow Head tui chub. Considering that these and other 
threats we identified in the March 30, 1998, proposed rule (63 FR 
15152) either (1) do not exist or (2) have been eliminated or otherwise 
ameliorated, we are withdrawing the proposal to list the species. For 
further information, please see the Summary of Factors Affecting the 
Species section below.
    (15) Comment: One commenter felt that conservation agreements fail 
to protect species adequately.
    Our Response: The Service believes conservation agreements (CAs) 
can serve a valuable role in helping to conserve species, and we also 
recognize that they may have limitations, as suggested by this comment. 
In the specific case of the Cow Head tui chub, the CA enabled the 
Service get additional valuable information on the species' status on 
private lands, and it provided a means for stakeholders to take an 
active role in the conservation of the species. This withdrawal of the 
proposed rule to list the Cow Head tui chub is not based on 
anticipation of future improvements in the status of the species that 
we believe will occur as a result of the CA. Instead, this withdrawal 
is based on new information that demonstrates a lack of identified 
treats, as is described below in the discussions of Factors A-E; this 
new information was obtained in large measure through implementation of 
the CA. More discussion of this topic is found under the sections 
titled ``Conservation Agreement'' above and ``Summary of Factors 
Affecting the Species'' below.

Conservation Review

    At the time the March 30, 1998, proposed rule was published (63 FR 
15152), little information was available regarding the Cow Head tui 
chub. The CA has allowed us to obtain more extensive and accurate 
information on the Cow Head tui chub, including its distribution, 
population status, habitat use, and land management in the Cow Head 
basin. The CA has also resulted in the initiation of management 
activities by private and public stakeholders, which further secure the 
Cow Head tui chub and its habitat.
    In 2005, in order to make a final determination on the listing 
status of the Cow Head tui chub given this crucial new information, we 
arranged for an independent scientific review of the Cow Head tui chub 
to obtain a comprehensive synthesis of all available data pertinent to 
the conservation of the species, including clarification of the 
complicated history and management of the basin, evaluation of 
biological information regarding the species, and compilation of 
previous population and habitat surveys in the basin. The purpose of 
the review was to assemble all scientific and commercial information on 
the Cow Head tui chub, as well as to assimilate the collective 
knowledge of local landowners and managers. The review did not evaluate 
the status of the Cow Head tui chub under the Act, as that is the 
Service's ultimate responsibility. The principal author of the review 
is Dr. Stewart Reid, an independent biologist, who is a recognized 
expert in the native fishes of this region and who is familiar with the 
Cow Head Basin. The review was peer reviewed in May-June 2006 and made 
available to stakeholders to ensure its accuracy and completeness (see 
Peer Review section, below). The revised synthesis (Reid 2006a) and its 
supporting documentation reflect the most recent information regarding 
the Cow head tui chub; this information significantly informs our 
determination to withdraw our previous proposal to list this subspecies 
(63 FR 15152, March 30, 1998).

Peer Review

    In accordance with our July 1, 1994, Interagency Cooperative Policy 
for Peer Review in Endangered Species Act Activities (59 FR 34270), we 
solicited the opinions of seven independent specialists. We provided 
the reviewers with the synthesis document (Reid 2006a) which contains 
new information, and a review of all available scientific, historical, 
and management information pertaining to the species. We specifically 
asked the reviewers to review the document for accuracy of the 
information, any missing information, and threats to the species not 
mentioned in the report. Reviewers were not asked to interpret the Act 
as it applies to this species or to make a recommendation as to the 
appropriate regulatory status for the Cow Head tui chub.
    The Service's Policy for Peer Review requires that we: (1) Solicit 
the expert opinions of a minimum of three appropriate and independent 
specialists regarding pertinent scientific and commercial data and 
assumptions relating to the taxonomy, population models, and supportive 
biological and ecological information for species under consideration 
for listing; and (2) summarize in the final decision document the 
opinions of all independent peer reviewers received on the species 
under consideration. The purpose of a peer review is to ensure that 
listing decisions are based on scientifically sound data, assumptions, 
and analyses, including input of appropriate experts and specialists.
    Peer reviewers included two senior research scientists familiar 
with the Cow Head tui chub and the Cow Head Basin (one from the 
University of California, Davis and one from U.S. Geological Survey--
Biological Resources Division, Reno), four scientists from agencies 
with management responsibilities in the Cow Head Basin (two from CDFG, 
one from BLM, and one from the U.S. Forest Service), and one 
representative of the Cow Head Irrigation District who could provide 
detailed information on local conditions, especially water management 
in the basin.
    All reviewers confirmed the accuracy and completeness of the 
scientific information in the synthesis. Two reviewers (BLM and Cow 
Head Irrigation District) helped clarify details of management and 
hydrology in the Cow Head Basin, which have been incorporated into the 
final document used for this analysis, along with minor editorial 
suggestions from the various reviewers. The reviewers did not identify 
any additional factors that might threaten the Cow Head tui chub.

Summary of Factors Affecting the Species

    Section 4 of the Act and its implementing regulations (50 CFR 424) 
establishes procedures for adding species to the Federal Lists of 
Endangered and Threatened Wildlife and Plants. A species may be 
determined to be an endangered or threatened species due to one or more 
of the five factors described in section 4(a)(1) of the Act: (A) The 
present or threatened destruction, modification, or curtailment of 
habitat or range; (B) overutilization for commercial, recreational, 
scientific, or educational purposes; (C) disease or predation; (D) the 
inadequacy of existing regulatory mechanisms; or (E) other natural or 
manmade factors affecting its continued existence. In making this 
finding, we evaluated whether any of these five factors are a threat to 
the continued existence of the Cow Head tui chub throughout all or a 
significant portion of its range. Our evaluation of these threats is 
presented below.

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

    In the 1998 proposed rule, reduction of historical range and 
modification of habitat were considered threats to the

[[Page 59706]]

Cow Head tui chub (63 FR 15153--54, March 28, 1998). We stated that the 
range had been reduced by 98 percent due to loss of Cow Head Lake. A 
better understanding of the basin's hydrology has shown that the lake 
still provides seasonal habitat in wet years and maintains permanent 
habitat in the lakebed canals (Reid 2006a, pp. 15-19).
    In 1998, we also stated that stream habitat was restricted to 5.4 
km (3.4 miles). New information developed by Reid (2006a, pp. 15-19) 
has shown that total linear stream and channel habitat was 
approximately 10.5 km (6.5 mi) in 2001, a very dry year (Scoppettone 
and Rissler 2006, p. 108). In the spring, and at times when there is 
sufficient water, the chub occupies the full lengths of the tributary 
streams (21.2 km; 13.2 mi).
    Current information, based on more complete basin-wide surveys, 
demonstrates that the Cow Head tui chub is more widely distributed than 
previously thought and maintains populations throughout all of its 
historical range in all streams and lakebed channels that would have 
offered suitable habitat in the past.
Range
    Based on our knowledge of historical conditions, the species' 
habitat needs, and its current distribution, we assume the natural 
historical range (geographical distribution) of the Cow Head tui chub 
would have encompassed all low gradient streams with perennial reaches 
in the Cow Head Basin of California and Nevada, including: Cow Head 
Lake, Cow Head Slough, Barrel Creek, West Barrel Creek, and Keno Creek 
(Reid 2006a, pp. 5-6 and 15-19). Based on knowledge of the chub's 
biology, it is logical to assume there was some natural dispersal 
downstream into the Twelvemile Creek drainage during higher springtime 
flows, as there apparently is today, but the fate of these individuals 
is not known (Reid 2006a, pp. 18-19). Within the Cow Head Basin, the 
primary distribution of tui chubs, based on habitat needs, would have 
included any low-energy aquatic habitats, including stream pools, 
emergent marshes with open water, and Cow Head Lake itself, when 
present (Moyle 2002, p. 124-125; Reid 2006a, p. 20). Because tui chubs 
show a preference for low-energy habitats such as pools, it is unlikely 
they would have typically occupied higher-energy stream reaches with 
steep gradients, strong flow, or shallow riffles (e.g., the lower 
canyon section of Cow Head Slough), although they might move through 
such habitats. They also would not have occupied higher gradient 
reaches of the western tributaries coming off the Warner Mountains 
(e.g., Eightmile and Ninemile creeks), which have cooler temperatures 
and are occupied by trout, Oncorhynchus mykiss, and speckled dace, 
Rhinichthys osculus (Hubbs 1934, p. 2; Sato 1992, p. 5).
    Recent surveys on public and private land, facilitated by the 1999 
CA, have documented the presence of Cow Head tui chub in all 
historically perennial water bodies (Minto 1879; see map and discussion 
in Reid 2006a, pp. 5-8) containing suitable habitat in the Cow Head 
Basin (Scoppettone and Rissler 2006, p. 5). In 2001, populations were 
found in all eastern tributaries (Keno, West Barrel, and Barrel Creeks, 
as well as Cow Head Slough), including private land that had not been 
previously surveyed, and a large population (estimated to be in the 
10,000s) exists on the historic lakebed in perennial canals 
(Scoppettone and Rissler 2002, p. 5; Reid 2006a, p. 22). Cow Head tui 
chub presumably disperse throughout Cow Head Slough and the various 
low-gradient tributaries in the spring and onto the lakebed when it is 
flooded, with their distribution contracting to the lakebed channels 
and perennial spring-fed stream reaches each year as the arid summer 
progresses. In 2001, a very dry year, perennial habitat occupied by the 
chub remained in all eastern tributaries (Keno Creek--0.5 km (0.3 mi) 
perennial, West Barrel Creek--1.0 km (0.6 mi) perennial, and Barrel 
Creek--4.0 km (2.5 mi) perennial), Cow Head Slough (approximately 3 km 
(1.9 mi) perennial) and the two principal lakebed channels (Pump and 
Eightmile canals--2 km (1.2 mi) perennial) (Scoppettone and Rissler 
2006, pp.108-109; Reid 2006a, pp. 16-18).
Habitat--Streams
    Stream populations of Cow Head tui chub primarily occupy pool 
habitats, and available habitat area varies depending on the time of 
year and degree of drought severity (Homuth 2000, p. 10; Scoppettone 
and Rissler 2006, p.109). Historically, there were four low gradient 
stream drainages in the Cow Head Basin that had perennial flow and 
would have contained suitable Cow Head tui chub habitat; all still 
maintain Cow Head tui chub populations (Reid 2006a, pp. 15-19; 
Scoppettone and Rissler 2002, p. 5; Scoppettone and Rissler 2006, p. 
109). These drainages are currently referred to as Cow Head Slough, 
which forms the outlet for the Cow Head Basin; Barrel Springs and West 
Barrel, both of which entered Cow Head Lake itself from the east in 
1879; and Keno Spring, which enters Cow Head Slough from the east 
before it drops into the higher-gradient canyon section. All contain 
locally perennial pool habitat, which is naturally maintained by small 
springs.
    Cow Head Slough flows out of Cow Head Lake. After flowing about 5 
km (3.1 mi) to the north, the slough enters a short, half-mile-long 
canyon and then joins Twelvemile Creek in the Warner Basin. 
Historically, the slough apparently contained water along most of its 
length into the summer (Minto 1879; see map and discussion in Reid 
2006a, pp. 5-8), but Minto's survey notes do not mention actual flow 
conditions, and local ranchers interviewed in the 1930s reported that 
the slough overflowed only during high spring runoff periods (Hubbs 
1934, p. 1).
    Under present management, Cow Head Slough only flows into 
Twelvemile Creek during the springtime runoff period and while the 
lakebed is being pumped down, with most continuous stream flow 
typically ending by late May or early June. Pools with marshy margins 
and herbaceous riparian vegetation are present all along the length of 
the slough, with perennial spring-fed reaches concentrated in the 
southern (upstream) 3 km (1.9 mi). The Barrel Springs drainage also 
carries considerable runoff in the spring, but summer flows are low, 
and in the 1879 Minto surveys, the stream channel did not have 
perennial flow between the Nevada border and Cow Head Lake (see Minto 
map in Reid 2006a, p. 6). Likewise, the Keno Springs drainage near its 
confluence with Cow Head Slough was surveyed by Minto in 1879, and was 
noted simply as a meadow with no creek.
    The Cow Head Basin is in an arid landscape. (See Factor E--Natural 
Drought, below). Although surface water is present throughout most of 
the basin in the early spring, hot and dry summer conditions naturally 
reduce the quantity of aquatic habitat progressively through the summer 
and early fall. In drier years, much of Cow Head Slough and the reaches 
of tributary streams without perennial springs are reduced to isolated 
pools which often dry up. Permanent pool habitat suitable for Cow Head 
tui chubs is restricted to reaches maintained by perennial springs. 
Under historical conditions channel desiccation may have been retarded 
in Cow Head Slough by the storage capacity of the lake and associated 
wetlands, and in other streams by narrow wet meadows along the riparian 
corridors. However, in most dry years when the lake was not overflowing 
during the summer (which is similar to the current situation under 
present management), desiccation and loss of aquatic habitat would have 
progressed

[[Page 59707]]

in a manner similar to that experienced today; by late summer, 
available stream habitat would have been limited to perennial spring-
fed reaches of Cow Head Slough and the three eastern tributaries 
(Barrel, West Barrel and Keno creeks). All spring-fed reaches of the 
slough and the three eastern tributaries currently maintain perennial 
tui chub populations (Scoppettone and Rissler 2006, p. 109).
    The only direct modification of streams containing Cow Head tui 
chub occurred in the 1930s with the dredging of Cow Head Slough for a 
distance of about 1.3 km (0.8 mi) downstream of Cow Head Lake, and with 
construction of an earthen levy on the east side to divert flow from 
the eastern watershed (West Barrel and Barrel Spring drainages) 
directly into Cow Head Slough near the historical outlet of Cow Head 
Lake (Reid 2006a, p.8). These modified reaches have since developed 
into stream reaches with vegetated riparian corridors. There are no 
water diversions in Cow Head Slough or the eastern tributary streams. 
Modification of grazing management in the last decade has produced 
notable improvements and continuing upward trends in channel stability, 
riparian vegetation, and aquatic habitat quality (USBLM 1996, p. 2; 
USBLM 2003, p. 9; Reid 2006a, pp. 10, 15-16).
Habitat--Cow Head Lake
    In 1879 a shallow lake covered much of the Cow Head valley floor 
(Minto 1879, pp. 47, 56, 59; see map, Reid 2006a, p. 8). The maximum 
depth of the lake was not recorded, but general depths of 40-60 cm (15-
24 in) were noted. Its northwestern and southeastern shores were 
bounded by belts of wet meadow and tule marshes, which are dominated by 
hardstem bulrush (Scirpus acutus), as was the outlet channel for a 
distance of about 4 km (2.5 mi) north along Cow Head Slough, which 
carried overflow north to a short canyon where it entered Twelvemile 
Creek and the southern Warner Basin. The lake was fed primarily by snow 
runoff in the spring from the Warner Mountains to the west and the 
Barrel Creek and West Barrel Creek drainages in the lower hills to the 
east. Summer and fall inputs to the lake would have been limited to 
ground-water-fed base flows of Eightmile Creek, which is supplemented 
by perennial springs in its lower reaches, and other small perennial 
springs in the immediate vicinity of the lake (Reid 2006, pp. 5-8). The 
original survey map shows only Eightmile Creek and the short spring-fed 
West Barrel Creek as providing flow into the lake in July 1879. 
Ninemile Creek, which currently does not reach Cow Head Lake during the 
summer, was shown as a ``brook'' with no surface flow closer than about 
0.8 km (0.5 mi) to the west of the lake on the 1879 survey map drawn by 
Minto (Reid 2006a, pp. 6-7). Barrel Creek, which contains perennial 
springs in its middle and upper reaches, apparently did not reach the 
lake in July 1879. Although Cow Head Lake and its associated emergent 
marsh historically provided extensive aquatic habitat during some 
years, it was not a permanent feature. Regional, climatic, and 
historical evidence suggests that Cow Head Lake itself would have 
periodically dried up (Reid 2006a, pp. 8, 26-27). (For additional 
information, see Factor E--Natural Drought, below.)
    Modification of the western tributaries to Cow Head Lake began in 
the late 1800s with the diversion of the upper reaches of Eightmile 
Creek itself to the south into Lake Annie (Reid 2006a, pp. 7-10). The 
upper Eightmile drainage would have historically provided considerable 
spring snow runoff into Cow Head Lake; however, late summer base flows 
from that elevation are minimal following loss of the snow pack. The 
lower Eightmile drainage is now primarily fed by the Schadler Ditch 
(built around 1904), which captures runoff from Mount Bidwell (not 
originally part of the Cow Head Basin) and carries it into Schadler 
Creek (labeled as Eightmile Creek on the U.S. Geological Survey, Lake 
Annie Quadrangle). Schadler Reservoir, which is approximately 250 acre-
feet in size and was built in the 1960s, collects the flow of Schadler 
Creek and numerous small springs about 1.6 km (1 mi) upstream of the 
lake. Water from the reservoir (about 50 acre-feet/month) is used 
throughout the summer to irrigate downstream pastures, which drain into 
the Cow Head lakebed channels, or is sent downstream to maintain water 
in the lakebed channels themselves.
    In the 1930s, following a period of extended drought, alterations 
were made to the lakebed to allow drainage of the lake in the spring 
for agricultural use. Three channels were dug to carry water out of the 
lakebed. The first comes from the center of the lake to the northwest 
(here referred to as Lakebed Canal), where it meets a second channel 
carrying flow from the Eightmile drainage (Eightmile Canal), and then 
enters a third channel (Pump Canal, also known as Cow Head Ditch) that 
runs 1 km (0.6 mi) northeast to a pumping station. At that point, water 
is pumped past a weir into a continuation of the channel (Discharge 
Channel) that continues on to Cow Head Slough. The outlet of Cow Head 
Lake into Cow Head Slough was also dredged in the 1930s for a distance 
of about 1.3 km (0.8 mi), and an earthen levy was constructed on the 
east side to divert flow from the eastern watershed (West Barrel and 
Barrel Spring drainages) directly into Cow Head Slough, reducing runoff 
into the lakebed.
    Cow Head Lake is now flooded only in the springtime, when it 
receives local snowmelt and rain, as well as runoff primarily from the 
western slopes of the basin. Most runoff from the eastern tributaries 
either flows naturally (Keno Creek) or is now diverted by the earthen 
levy (Barrel and West Barrel Creeks) into Cow Head Slough. There was 
enough water to fill the lake in the mid-1980s, 1997, and 2006. When 
extensive standing water is present, it is pumped off the lakebed by 
May or June to allow for growth of hay or pasture grass. Pumping has 
not been necessary for more than a few days since about 1999; however, 
the high runoff year of 2006 required about 30 days of pumping to bring 
water levels off the lakebed and into the channels. During the summer, 
irrigation water is supplemented by local groundwater inputs and water 
brought down the Eightmile system with releases of water from Schadler 
Reservoir and perennial spring flow.
    Perennial aquatic habitat on the lakebed is contained within the 
canals above the pump. The canal channels are about 10 meters (m) (33 
ft) wide, with a depth up to about 4 m (13 ft). The Pump Canal is 
approximately 1 km (0.6 mi) long and contains water throughout the 
summer. Suitable chub habitat in Eightmile Canal is slightly less than 
1 km (0.6 mi) long; while this reach has not been specifically surveyed 
for Cow Head tui chubs, it receives high quality water from the 
Eightmile drainage and carries it into the Pump Canal. The Lakebed 
Canal is approximately 1.3 km (0.8 mi) long; however this channel dries 
up through the summer, after water is pumped down off the lakebed, and 
rarely contains water much upstream of the confluence with the Pump 
Channel. Although the lakebed is no longer characterized by extensive 
emergent marsh habitat, the canals contain submerged aquatic vegetation 
that provides food, cover, and spawning habitat for the chub.
    Modifications to the natural hydrology of Cow Head Lake, which 
occurred in the late 1800s and early 1900s, altered the characteristics 
and availability of suitable habitat for the Cow Head tui chub on the 
lakebed (reviewed in Reid 2006a, pp. 5-9). The annual diversion and 
pumping of water from Cow Head Lake, initiated in the

[[Page 59708]]

late 1930s, eliminated the opportunity for continuous utilization of 
lake and peripheral marsh habitat in wet years when the lake would have 
otherwise filled. However, the Cow Head Basin historically went through 
periods of extended drought, during which the lake would have 
contracted or dried completely. During these periods, available Cow 
Head tui chub habitat would have been restricted to stream reaches fed 
by perennial springs, as it currently is during dry years.
    Some of the modifications to the lakebed now actually serve to 
maintain perennial habitat on the lakebed, which would not have been 
available to the fish prior to the modifications. The present-day 
lakebed channels, which provide approximately 2 km (1.2 mi) of 
perennial habitat, are deeper than the historical lakebed, and water 
management practices that maintain suitable habitat in the canals 
during dry periods have actually expanded the habitat available to the 
Cow Head tui chub during droughts (Reid 2006a, p. 9). The Cow Head tui 
chub population in the lakebed channels presumably still disperses onto 
the lakebed when it is flooded in the spring, as there are no barriers 
that would prevent such movement.
Land Management
    The Cow Head lakebed was generally farmed for grain from 1924 until 
about 1980, when farming was discontinued (Reid 2006a, p. 10). Since 
then, the lakebed has been managed solely for grazing and hay 
production, with no tillage and no application of fertilizers or 
pesticides. Changes in land management within the basin have resulted 
in a generally upward trend for Cow Head tui chub habitat. These 
changes include: (1) Runoff storage in west-side reservoirs to 
supplement late-season water supplies for the western channels; (2) the 
termination of farming and switch to grazing management on the lakebed 
itself in the early 1980s, which has resulted in reduced sedimentation 
in the lakebed channels and Cow Head Slough; (3) modifications in 
grazing management on public and private lands, which have resulted in 
improved conditions within stream corridors and upward trending 
riparian vegetation conditions; (4) acquisition of an additional 80-
acre parcel by BLM in 2003, which places it under management guidelines 
established to improve aquatic and riparian habitat, including about 
0.5 km (0.3 mi) of occupied habitat in Cow Head Slough containing 
perennial springs and permanent pools (USBLM 2003, p. 4; Reid 2006a, p. 
10); and (5) ongoing cooperation between public and private 
stakeholders under a CA signed in 1999 with the stated purpose of 
conserving the Cow Head tui chub. Landownership in the basin is limited 
to seven families and the BLM, with most land dedicated to hay and 
grazing. Based on our knowledge of the area and on the general 
stability of the local ranching community, we know of no reason why 
current land use is likely to substantially change in the foreseeable 
future.
Factor A Conclusion
    The range of the Cow Head tui chub has not changed substantially 
since 1879. Modification of low-gradient stream habitat in the Cow Head 
Basin occurred primarily in the early 20th century, with channelization 
of the southern end of Cow Head Slough in the 1930s and continued 
livestock grazing. Current management of riparian corridors has 
resulted in upward habitat trends (USBLM 1996, p. 2; USBLM 2003, p. 9; 
Reid 2006a, pp. 10, 15-16), and there has been no substantial loss of 
perennial stream habitat for the Cow Head tui chub. In contrast, the 
character of Cow Head Lake has changed considerably since the 1800s, 
with the dewatering of the lake and its associated emergent marshes as 
a generally perennial, though intermittent, landscape feature. However, 
even prior to such changes, Cow Head Lake would have been dry and would 
have provided no habitat during past periods of natural drought when 
the Cow Head tui chub population would have been most stressed by 
environmental conditions.
    During natural droughts, perennial stream reaches associated with 
permanent springs provided habitat for the Cow Head tui chub, as they 
do today (Scoppettone and Rissler 2006, p. 109). Furthermore, 
management of the Cow Head Basin has been essentially stable since the 
late 1930s, following a 16-year period (1923-1938) of drought when the 
entire lake was naturally dry; during that time a large population of 
Cow Head tui chub nevertheless sustained itself throughout the basin 
and specifically in the drainage canals on the lakebed (Reid 2006a, pp. 
5-10; Scoppettone and Rissler 2006, pp. 108-109).
    There is no reason to expect substantial negative changes to the 
current management regime. Habitat conditions are generally upward 
trending and private and public land managers have incorporated and are 
continuing to implement strategies that have enhanced the availability 
of permanent water and suitable habitat for Cow Head tui chub (USBLM 
1996, p. 2; USFWS 1999, pp. 2, 12; USBLM 2003, p. 9; Reid 2006a, pp. 
10, 15-16). Therefore, destruction, modification, or curtailment of its 
habitat or range is not likely to threaten the Cow Head tui chub with 
extinction throughout all or a significant portion of its range within 
the foreseeable future.

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

    Overutilization was not considered a threat to the species in the 
1998 proposed rule (63 FR 15154). The Cow Head tui chub is not a 
commercial or recreational fish species, and there have been only a few 
documented scientific collections since 1939 (Reid 2006a, pp. 37-38). 
Future collections for scientific purposes presumably would be limited 
to small collections for genetic, morphological, or life history 
studies, and these would not substantially affect the population as a 
whole. Therefore, over-utilization is not likely to threaten the Cow 
Head tui chub with extinction throughout all or a significant portion 
of its range within the foreseeable future.

C. Disease or Predation

    In the 1998 proposed rule, we indicated that the potential 
introduction of a catastrophic disease or a nonnative predatory fish 
could be harmful to Cow Head tui chub, particularly due to the small 
estimated population size and confined known range of the Cow Head tui 
chub at that time (63 FR 15154). We also noted that there were no 
documented instances of disease actually affecting the tui chub or 
detections of nonnative predatory fish in tui chub habitat. This factor 
was not considered a principal threat to the species.
    The potential introductions of a disease or nonnative predators to 
the Cow Head Basin would be subject to a number of constraints that 
greatly reduce the likelihood of such occurrence and also reduce the 
likelihood that a nonnative predator would become established if 
introduced. These constraints include: (1) The isolated location of the 
Cow Head Basin; (2) the absence of existing nonnative fish populations 
in the basin; (3) the habitat characteristics of upper Twelvemile Creek 
(high gradient, cool water) and the lower canyon reach of Cow Head 
Slough (high gradient, generally dry or low flow, with no upstream 
passage except possibly during high spring flows), both of which would 
impede the upstream invasion of warm-water game fish from the Warner 
Valley floor; (4) the absence of source water bodies suitable for warm-
water

[[Page 59709]]

sport fishing (e.g., reservoirs) in the basin (all permanent reservoirs 
in the Basin are at higher elevations and contain cold water suitable 
only for trout); (5) the warm water habitat characteristic of the lower 
elevation streams containing Cow Head tui chub are not suitable for 
establishment of nonnative trout; (6) the location of perenn