Endangered and Threatened Wildlife and Plants; Proposed Removal of the Concho Water Snake (Nerodia paucimaculata) From the Federal List of Endangered and Threatened Wildlife; Removal of Federally Designated Critical Habitat, 38956-38967 [E8-15133]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 73, Number 131 (Tuesday, July 8, 2008)]
[Proposed Rules]
[Pages 38956-38967]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-15133]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R2-ES-2008-0080; 92220-1113-0000; C6]
RIN 1018-AU97


Endangered and Threatened Wildlife and Plants; Proposed Removal 
of the Concho Water Snake (Nerodia paucimaculata) From the Federal List 
of Endangered and Threatened Wildlife; Removal of Federally Designated 
Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: The best available scientific and commercial data indicate 
that the Concho water snake (Nerodia paucimaculata) has recovered. 
Therefore, under the authority of the Endangered Species Act of 1973, 
as amended (Act), we, the U.S. Fish and Wildlife Service (Service) 
propose to remove (delist) the Concho water snake (Nerodia 
paucimaculata) from the Federal List of Endangered and Threatened 
Wildlife, and accordingly, also remove its federally designated 
critical habitat. This determination is based on a thorough review of 
all available information, which indicates that the threats to this 
species have been eliminated or reduced to the point that the species 
has recovered and no longer meets the definition of threatened or 
endangered under the Act.
    The Concho water snake is a reptile endemic to central Texas. It 
was listed as threatened on September 3, 1986, due to threats of 
habitat modification and destruction (51 FR 31412). Through 
implementation of recovery efforts, the Service has determined that 
this species has been recovered and no longer meets the definition of 
threatened or endangered.

DATES: Comments on the proposed rule must be received on or before 
September 8, 2008. Public hearing requests must be received by August 
22, 2008.

ADDRESSES: You may submit comments by one of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov. 
Follow the instructions for submitting comments.
     U.S. mail or hand-delivery: Public Comments Processing, 
Attn: 1018-AU97, Division of Policy and Directives Management; U.S. 
Fish and Wildlife Service; 4401 N. Fairfax Drive, Suite 222; Arlington, 
VA 22203.
    We will post all comments on https://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see the Public Comments section below for more information).

FOR FURTHER INFORMATION CONTACT: Adam Zerrenner, Field Supervisor, U.S. 
Fish and Wildlife Service, Austin Ecological Services Field Office, 
10711 Burnet Road, Suite 200, Austin, TX 78758; telephone 512/490-0057, 
extension 248; facsimile 512/490-0974. Persons who use a 
telecommunications device for the deaf (TDD) may call the Federal 
Information Relay Service (FIRS) at 800/877-8339, 24 hours a day, 7 
days a week.

SUPPLEMENTARY INFORMATION:

Public Comments Solicited

    Our intent is to use the best available commercial and scientific 
data as the foundation for all endangered and threatened species 
classification decisions. Comments or suggestions from the public, 
other concerned governmental agencies, the scientific community, 
industry, or any other interested party concerning this proposed rule 
to delist the (species name) are hereby solicited. Comments 
particularly are sought concerning:
    (1) Any threat (or lack thereof) to the Concho water snake;
    (2) Additional information on the range, distribution, and location 
of any additional populations of the Concho water snake;
    (3) Information on habitat destruction and/or preservation for the 
Concho water snake;
    (4) Current or planned activities in the species' habitat and the 
possible impacts to the Concho water snake;
    (5) Data on population trends;
    (6) Data on the status of Concho water snakes in reservoirs;
    (7) Information regarding the sufficiency of planned flows in the 
Colorado River to maintain habitat for the Concho water snake;
    (8) Data on the need for movement of Concho water snakes around 
large dams to maintain genetic diversity; and

[[Page 38957]]

    (9) Information pertaining to the design of the required post 
delisting monitoring.
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. Comments 
must be submitted to https://www.regulations.gov before midnight 
(Eastern Standard Time) on the date specified in the DATES section. 
Please note that we may not consider comments we receive after the date 
specified in the DATES section in our final determination.
    Before including your address, phone number, e-mail address, or 
other personal identifying information in your comment, you should be 
aware that we will post your entire comment--including your personal 
identifying information--on https://www.regulations.gov. While you can 
ask us in your comment to withhold your personal identifying 
information from public review, we cannot guarantee that we will be 
able to do so.
    In making a final decision on this proposal, we will take into 
consideration the comments and any additional information we receive. 
Such communications may lead to a final rule that differs from this 
proposal.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on https://www.regulations.gov, or by 
appointment, during normal business hours at the Austin Ecological 
Services Field Office (see FOR FURTHER INFORMATION CONTACT section).

Public Hearing

    The Act provides for one or more public hearings on this proposal, 
if requested. Requests must be received by August 22, 2008. Such 
requests must be made in writing and addressed to the Field Supervisor 
(see FOR FURTHER INFORMATION CONTACT section).

Background

    The Concho water snake is endemic to the Colorado and Concho Rivers 
in central Texas (Tennant 1984, p. 344; Scott et al. 1989, p. 373). It 
occurs on the Colorado River from E.V. Spence Reservoir to Colorado 
Bend State Park, including Ballinger Municipal Lake and O.H. Ivie 
Reservoir, and on the Concho River from the City of San Angelo to its 
confluence with the Colorado River at O.H. Ivie Reservoir. The Concho 
water snake can be found in rivers and streams, and on artificial 
shoreline habitat of the three reservoirs. Counties of known occurrence 
include Brown, Coke, Coleman, Concho, Lampasas, McCulloch, Mills, 
Runnels, San Saba, and Tom Green.
    At the time of listing, there were considered to be two subspecies 
of Nerodia harteri, the Concho water snake (N. h. paucimaculata) and 
the Brazos water snake (N. h. harteri). Densmore et al. (1992, p. 66) 
determined the Concho water snake was a distinct species based, in 
part, on its geographic isolation and fixed differences in genetic 
markers. Therefore, in 1996 we changed the name in the Federal List 
from N. h. paucimaculata to N. paucimaculata (50 CFR 17.11) in 
accordance with Densmore et al. (1992). Information about the Concho 
water snake's biology and life history can be found in the final 
listing rule (51 FR 31412-1422), the Concho Water Snake Recovery Plan 
(Service 1993, pp. 4-5), Werner and Dixon (2000, pp. 209-216), and 
Campbell (2003).
    In 1998, the Colorado River Municipal Water District (District) 
(1998, pp. 8-29) summarized 10 years of data collected on Concho water 
snake populations, status, and distribution. In 2004, the U.S. 
Geological Survey (USGS) analyzed capture-recapture data from 3 
sources: (1) Mueller (1990, pp. 18-27); (2) Whiting (1993, Appendix 1); 
and (3) the 10 years of District data. However, for a number of 
reasons, primarily insufficient sampling effort at any single study 
site and a host of variables, especially environmental variability 
within a site and among sites, study results have not been robust 
enough to allow either population or trend estimates with satisfactory 
precision (Service 2004, p. 23). Additional information, particularly 
concerning the habitat requirements of the Concho water snake, is 
discussed under Summary of Factors Affecting the Species below.
    The Concho water snake is characterized by being somewhat smaller 
than most other Nerodia. At maturity, males average about 15 inches 
(in) (38.1 centimeters (cm)) snout-vent length (SVL), and females 
average about 18 in (45.7 cm) SVL, with a maximum reported length of 42 
in (106.7 cm) SVL. Hibernation begins in late October to late November, 
depending upon weather and temperatures (Williams 1969, p. 11). Most 
adults probably hibernate in the tunnels of small burrowing animals, 
particularly crayfish, while hibernating juveniles may be more common 
in the crevices under rocks on gravel bars (Werler and Dixon 2000, pp. 
212, 214). Males reach sexual maturity at about 1 year of age but 
females produce their first litter at 2 or 3 years of age, depending on 
their reproductive development (Werler and Dixon 2000). The snakes 
emerge from mid-March to mid-April for the main mating event, which 
occurs during April and early May, with a lesser event in October 
(Greene et al. 1999, p. 702; Williams 1969, p. 11). Most births occur 
from late July through September (Dixon et al. 1988, p. 15; 1990, p. 
13; 1991, pp. 30-31; 1992, p. 28; Greene et al. 1999, p. 702). Females 
produce litter sizes that range from 4 to 29, with a mean of about 11 
neonate snakes (Greene et al. 1999).
    Concho water snakes feed almost exclusively on fish (Williams 1969, 
pp. 9-10; Dixon et al. 1988, p. 16; 1989, p. 8; 1990, p. 36; 1992, p. 
6; Greene et al. 1994, p. 167; Thornton 1990, p. 14), and have been 
observed feeding both during the day and at night. In riverine habitat 
and especially among neonates (recently born snakes), minnows (fish in 
the Cyprinidae family) are the primary food source. Concho water snakes 
may also opportunistically feed on frogs (Rana and Acris spp.) (Greene 
1993, p. 20).

Previous Federal Action

    We classified the Concho water snake as threatened on September 3, 
1986 (51 FR 31412). The primary reasons for listing were extensive 
habitat loss and imminent threats to a large portion of its remaining 
population. Critical habitat was designated on June 29, 1989 (54 FR 
27377). In September 1993, we finalized a recovery plan for the Concho 
water snake (Service 1993). In June 1998, we received a petition to 
delist the Concho water snake from the District. On August 2, 1999, we 
published a 90-day petition finding that the petitioner did not present 
substantial information indicating that delisting the species may be 
warranted (64 FR 41903).

Recovery

    Section 4(f) of the Act directs us to develop and implement 
recovery plans for listed species unless the Director determines that 
such a plan will not benefit the conservation of the species. The 
Service completed the Concho Water Snake Recovery Plan in 1993. The 
Concho Water Snake Recovery Plan outlines recovery criteria to assist 
in determining when the snake has recovered to the point that the 
protections afforded by the Act are no longer needed (Service 1993, p. 
33). These criteria are: (1) Adequate instream flows are assured even 
when the species is delisted. (2) Viable populations are present in 
each of the three major reaches (the Colorado River above Freese Dam, 
Colorado River below Freese Dam, and the Concho River). Here, 
population is defined as all Concho water snakes in a given area, in 
this case, each major river reach. (3)

[[Page 38958]]

Movement of an adequate number of Concho water snakes is assured to 
counteract the adverse impacts of population fragmentation. These 
movements should occur as long as Freese Dam is in place or until such 
time that the Service determines that Concho water snake populations in 
the three reaches are viable and ``artificial movement'' among them is 
not needed.
    We used the recovery plan to provide guidance to the Service, State 
of Texas, and other partners on methods to minimize and reduce the 
threats to the Concho water snake and to provide measurable criteria 
that would be used to help determine when the threats to the Concho 
water snake had been reduced so that it could be removed from the 
Federal List of Endangered and Threatened Wildlife.
    Recovery plans in general are not regulatory documents and are 
instead intended to provide a guide on how to achieve recovery. There 
are many paths to accomplishing recovery of a species in all or a 
significant portion of its range. The main goal is to remove the 
threats to a species, which may occur without meeting all recovery 
criteria contained in a recovery plan. For example, one or more 
criteria may have been exceeded while other criteria may not have been 
accomplished. In that instance, the Service may judge that, overall, 
the threats have been reduced sufficiently, and the species is robust 
enough, to reclassify the species from endangered to threatened or 
perhaps to delist the species. In other cases, recovery opportunities 
may be recognized that were not known at the time the recovery plan was 
finalized. Achievement of these opportunities may be counted as 
progress toward recovery in lieu of methods identified in the recovery 
plan. Likewise, we may learn information about the species that was not 
known at the time the recovery plan was finalized. The new information 
may change the extent that criteria need to be met for recognizing 
recovery of the species. Overall, recovery of a species is a dynamic 
process requiring adaptive management. Judging the degree of recovery 
of a species is also an adaptive management process that may, or may 
not, fully follow the guidance provided in a recovery plan.
    For more information on recovery of the Concho water snake, see the 
recovery plan at https://ecos.fws.gov/docs/recovery_plan/930927b.pdf. 
We caution that research conducted since the recovery plan was 
completed in 1993 has modified our understanding of habitat requirement 
of the species.
    A review of the best scientific and commercial data currently 
available (see Summary of Factors Affecting the Species section below) 
indicates that all three criteria in the Concho water snake recovery 
plan (adequate instream flows even after delisting, viable populations 
in each of the three major river reaches, and movement of snakes to 
assure adequate genetic mixing) have been met. Further, recovery of the 
Concho water snake has been a dynamic process, which has been furthered 
by the significant amount of new data collected on the biology and 
ecology of the species by numerous species experts. Since the time of 
listing and completion of the recovery plan, biologists have discovered 
that the snakes are able to persist and reproduce in the shorelines of 
reservoirs and that the snakes have managed to persist in all three 
population segments, surviving many years of drought. Based on this new 
information, the analysis below considers the best available data in 
determining that the Concho water snake may no longer meet the 
definition of a threatened or endangered species.

Summary of Factors Affecting the Species

    Section 4 of the Act and its implementing regulations (50 CFR part 
424) set forth the procedures for listing, reclassifying, or removing 
species from listed status. ``Species'' is defined by the Act as 
including any species or subspecies of fish or wildlife or plants, and 
any distinct vertebrate population segment of fish or wildlife that 
interbreeds when mature (16 U.S.C. 1532(16)). Once the ``species'' is 
determined, we then evaluate whether that species may be endangered or 
threatened because of one or more of the five factors described in 
section 4(a)(1) of the Act. We must consider these same five factors in 
delisting a species. We may delist a species according to 50 CFR 
424.11(d) if the best available scientific and commercial data indicate 
that the species is neither endangered nor threatened for the following 
reasons: (1) The species is extinct; (2) the species has recovered and 
is no longer endangered or threatened (as is the case with the (Concho 
water snake)); and/or (3) the original scientific data used at the time 
the species was classified were in error.
    A recovered species is one that no longer meets the Act's 
definition of threatened or endangered. Determining whether a species 
is recovered requires consideration of the same five categories of 
threats specified in section 4(a)(1) of the Act. For species that are 
already listed as threatened or endangered, this analysis of threats is 
an evaluation of both the threats currently facing the species and the 
threats that are reasonably likely to affect the species in the 
foreseeable future following the delisting or downlisting and the 
removal or reduction of the Act's protections.
    A species is ``endangered'' for purposes of the Act if it is in 
danger of extinction throughout all or a ``significant portion of its 
range'' and is ``threatened'' if it is likely to become endangered 
within the foreseeable future throughout all or a ``significant portion 
of its range.'' The word ``range'' in the phrase ``significant portion 
of its range'' (SPR) refers to the range in which the species currently 
exists. For the purposes of this analysis, we will evaluate whether the 
currently listed species, the Concho water snake, should be considered 
threatened or endangered throughout all of its range. Then we will 
consider whether there are any portions of the Concho water snake's 
range in which it is in danger of extinction or likely to become 
endangered within the foreseeable future.
    For the purposes of this proposed rule, we consider ``foreseeable 
future'' for the Concho water snake to be 20 years. This is a 
reasonable timeframe for analysis of factors identified that could 
affect the species in the future and as they relate to Concho water 
snake biology. The snakes become sexually mature at 2 or 3 years old 
and reproduce annually (Werner and Dixon 2000, p. 216), with a likely 
life span rarely exceeding 5 years (Greene et al. 1999, p. 707). A 20-
year timeframe would encompass about 4 life spans and multiple 
generations. Twenty years or about four life spans and multiple 
generations is a reasonable duration for analysis of hydrologic 
conditions and expected responses by a short lived species such as the 
Concho water snake. Factors most likely affecting the populations 
relate to hydrologic cycles and stream flows. Texas water law 
requirements, including the District's permit (TCEQ permit 
3676), requires minimum flows below Ivie Reservoir that are 
the same as those the Service found in our 2004 Biological Opinion were 
the minimum needed by the Concho water snake. In 2008 the Service 
entered into a Memorandum of Understanding (MOU) with the District to 
provide for the maintenance of minimum flow releases in perpetuity (see 
the Floodwater Scouring and Instream Flows section under Factor A for 
further discussion of the TCEQ permit and MOU). Therefore, we have no 
reason to believe that any significant changes are expected in the next 
20 years in reservoir operations or other

[[Page 38959]]

factors that might affect stream conditions and snake populations.
    The following analysis examines all five factors currently 
affecting, or that are likely to affect, the Concho water snake within 
the foreseeable future.

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

Habitat and Distribution
    Concho water snakes are known to occur in rivers, streams, and 
along the artificial shoreline of reservoirs. These snakes are air-
breathing; however, they feed almost exclusively on fish and are, 
therefore, found only near water sources capable of supporting at least 
a minimal fish population. Stream and river habitat used by the Concho 
water snake is primarily associated with riffles (Greene 1993, p. 96; 
Werler and Dixon 2000, p. 210; Forstner et al. 2006, p. 13), where the 
water is usually shallow and the current is of greater velocity than in 
the connecting pools. Riffles begin when an upper pool overflows at a 
change in gradient and forms rapids. The stream flows over rock rubble 
or solid to terraced bedrock substrate through a chute channel that is 
usually narrower than the streambed. The riffle ends when the rapids 
enter the next downstream pool. Riffles are believed to be the favored 
habitat for foraging, with young snakes using shallow parts of riffles 
and adult snakes using deeper parts of riffles (Greene 1993, pp. 13, 
96; Scott et al. 1989, pp. 380-381; Williams 1969, p. 8; Werler and 
Dixon 2000, p. 215; Forstner et al. 2006, p. 13). Searches on the 
mainstream rivers (Concho and Colorado) also indicated Concho water 
snakes were found in the shallow pools between riffles (Williams 1969, 
p. 8). Dixon et al. (1989, p. 16) demonstrated that adult snakes used a 
variety of cover sites for resting, including exposed bedrock, thick 
herbaceous vegetation, debris piles, and crayfish burrows.
    In the reservoirs, Concho water snake habitat is most likely 
shallow water with minimal wave action and rocks along the shoreline 
(Scott et al. 1989, pp. 379-380; Whiting 1993, p. 112). However, Concho 
water snakes have also been observed on steep shorelines and around 
boat houses (Scott et al. 1989, p. 379; Whiting 1993, p. 112). Unlike 
many other species of Nerodia, Concho water snakes do not seem to move 
far from water (Werler and Dixon 2000, p. 208). During Greene's (1993, 
p. 96) visual and radiotelemetry surveys, all snakes occurred within 33 
feet (ft) (10 meters (m)) of water.
    Adult and maturing Concho water snakes use a wider range of 
habitats than do juveniles (Scott et al. 1989, pp. 379-381; Werler and 
Dixon 2000, p. 211; Williams 1969, p. 8). In reservoirs and lakes, 
juvenile Concho water snakes are generally found in low-gradient, 
loose-rock shoals adjacent to silt-free cobble. In streams and rivers, 
juveniles are found in gravel shallows or riffles (Rose 1989, pp. 121-
122; Scott et al. 1989, p. 379, Scott and Fitzgerald 1985, p. 35). This 
habitat is likely the best for juvenile snakes to successfully prey on 
small fish because the rocky shallows concentrate prey and are 
inaccessible to large predatory fish. The exposed rocky shoals act as 
thermal sinks, which may help keep the juvenile snakes warm and 
maintain a high growth rate (Scott et al. 1989, pp. 380-381).
    Historically the Concho water snake was known to occur in spotty 
distribution on the mainstem of the Colorado River below E.V. Spence 
Reservoir near the City of Robert Lee downstream to the F.M. 45 bridge 
and then not again until further downstream near the City of Bend 
(Tinkle and Conant 1961, pp. 42-43; Williams 1969, p. 3). On the Concho 
River and its tributaries, Concho water snakes were historically known 
from Spring Creek, Dove Creek, and the South Concho River, all upstream 
of the Twin Buttes Reservoir, and on the mainstem of the Concho River 
downstream from San Angelo to the confluence with the Colorado River 
(Marr 1944, pp. 486-487; Tinkle and Conant 1961, pp. 42-43). By the 
time the Concho water snake was federally listed, it had been 
extirpated from the tributaries above the City of San Angelo (Flury and 
Maxwell 1981, p. 31), and surveys had never located snakes in lakes or 
reservoirs (Scott and Fitzgerald 1985, pp. 17, 34). At the time of 
listing, the range of the snake included O.C. Fisher, Twin Buttes, and 
Spence reservoirs and one tributary creek reservoir, Ballinger 
Municipal Lake. A fifth reservoir, O.H. Ivie (formerly known as Stacy), 
was already planned for construction at the confluence of the Concho 
and Colorado Rivers and was expected to reduce the range of Concho 
water snakes by more than 50 percent (Scott and Fitzgerald 1985, pp. 
31, 35).
    By 1993, Scott et al. (1989, pp. 382, 384), Thornton (1992, pp. 3-
16), and Whiting (1993, pp.8, 28, 117-118, 121) determined the Concho 
water snake's distribution to be about 233 mi (375 km) (Service 1993, 
p. 9). Analysis for a 2004 amendment to the 1986 Biological Opinion 
(Service 2004, p. 32) summarized the known distribution of the Concho 
water snake to be the Colorado River from the confluence of Beals Creek 
(above Spence Reservoir), depending on reservoir stage, to downstream 
of Ivie Reservoir to Colorado Bend State Park, and on the Concho River 
downstream of the City of San Angelo to the confluence with the 
Colorado River. This is a total of about 280 mi (451 km) of river and 
about 40 mi (64 km) of reservoir shoreline. While the Concho water 
snake has been extirpated from some reaches of its historical 
distribution, mainly upstream of San Angelo (Flury and Maxwell 1981, p. 
31), since the time of listing it has been confirmed farther downstream 
from Ivie Reservoir and upstream from Spence Reservoir (Scott et al. 
1989, p. 384; and Dixon et al. 1988, p. 12; 1990, pp. 50, 62-65; 1991, 
pp. 60-67; 1992, pp. 84, 87, 96-97).
    In 2004 and 2005, Drs. Forstner and Dixon surveyed for Concho water 
snakes across the species' range. One goal of Forstner et al. (2006, 
pp. 4-5) was to evaluate whether viable Concho water snake populations 
existed in all three reaches of the Colorado and Concho rivers 
separated by Ivie Reservoir. To do this, snake localities were surveyed 
``for evidence of reproduction (one measure of sustainability).'' 
Persistence and reproduction were documented in the Concho River and 
upstream of Ivie Reservoir in the Colorado River. However, access below 
Ivie Reservoir was restricted by private property owners, preventing an 
intense assessment downstream of the impoundment. Regardless of limited 
access, females that exhibited signs of recently giving birth were 
collected from accessible areas, which Forstner et al. (2006, p. 18) 
considered technically sufficient to demonstrate persistence and 
reproduction downstream of Ivie Reservior. ``Even in the face of 
landscape scale or ecosystem wide stresses by severely reduced 
precipitation, increased human uses of instream flows, introduced 
species, and ever increasing human densities, the Concho water snake 
remains in the majority of the sites visited and continues to reproduce 
at those locations (Forstner et al. 2006, p. 18).'' Forstner et al. 
(2006, pp. 16-18, 20) state that ``self sustain[ed], seemingly viable 
populations in the Concho and Colorado Rivers at the end of a decade of 
monitoring'' occur in the three reaches of the snake's range.
Reservoir Inundation
    At the time of listing, we believed the construction of Ivie 
Reservoir would have two major impacts that would result in loss of 
Concho water snake

[[Page 38960]]

habitat: (1) above the dam, the rocky shoreline and riffle habitat 
would be inundated, and (2) below the dam, normal water flow would be 
curtailed, and floodwater scouring would be prevented (see the 
Floodwater Scouring and Instream Flows section below for discussion of 
below-dam effects). At that time, the Colorado River at the proposed 
Ivie Reservoir site was believed to support the highest concentration 
of Concho water snakes (Flurry and Maxwell 1981, pp. 36, 48; 51 FR 
31419). Outside of this area, the snake had been found only in isolated 
occurrences, which indicated a disjunct, fragmented distribution. The 
snake had not been collected in reservoirs or in the silted in riverine 
habitat below Spence Reservoir (Scott and Fitzgerald 1985, pp. 13, 28). 
It also had not been found in perennial tributaries except Elm Creek 
near Ballinger (Scott and Fitzgerald 1985, pp. 15, 34). Thus, we 
believed the inundation of the Ivie Reservoir would result in a 
substantial loss of habitat for the Concho water snake.
    As a result of a 1986 formal consultation conducted under section 7 
of the Act with the U.S. Army Corps of Engineers (USACE) on 
construction of Freese Dam to form Ivie Reservoir (1986 Biological 
Opinion), the District agreed to implement conservation measures that 
included, but were not limited to: Long-term monitoring of the snakes, 
completing life-history studies, maintaining specific flow regimes from 
Spence and Ivie reservoirs, creating six artificial riffles below 
Spence, and transplanting snakes between populations above and below 
Ivie Reservoir (Service 1986, pp. 12-24).
    As part of their long-term monitoring plan, District field 
biologists conducted extensive searches for the Concho water snake 
beginning in 1987. According to Dixon et al. (1988, p. 12; 1990, pp. 
50, 62-65; 1991, pp. 60-67; 1992, pp. 84, 87, 96-97), snakes have now 
been documented within and above Spence Reservoir, downstream of Spence 
Reservoir in the artificial riffles, at Ballinger Municipal Lake, the 
old Ballinger Lake, and the connecting channel between the two 
Ballinger lakes. The snake has also been documented in multiple 
locations on Elm Creek and two of its tributaries, Bluff Creek and 
Coyote Creek (Scott and Fitzgerald 1985, pp.14-15, 30; and Scott et al. 
1989, p. 384).
    Additionally, during the District's 10-year monitoring effort 
(1987-1997), snakes were regularly found in Spence, Ivie, and Lake 
Ballinger Reservoirs, a habitat type they were not known to occupy at 
the time of listing. Concho water snakes have continued to be found in 
reservoirs. Dixon's (2004, pp. 3-4) surveys in 2004 confirmed that 
snakes persist in Spence and Ivie Reservoirs, and, while Ballinger Lake 
had only a small pool of water (2 feet or less) in 2004 and no snakes 
were found, after rains in 2005 Forstner et al. (2006, p. 12) confirmed 
snake presence and reproductive activity within the lake. Whiting 
(1993, p. 17) stated that rocky shorelines were the single most 
important component of snake habitat in reservoirs, and that changes in 
water surface elevation of Spence Reservoir affect the availability of 
that shoreline habitat (Whiting 1993, p. 13). In discussing Spence 
Reservoir, Forstner et al. (2006, p. 17) states that, ``there are rocky 
outcrops, boulder slopes, in limited areas that have been occupied by 
the snake and the populations have remained there over the past 
decade.''
    Because Concho water snakes are now known to be reproducing and 
persisting in lakes and reservoirs and their current distribution is 
larger than reported at the time of listing and historically, habitat 
loss from reservoir inundation is no longer believed to be a 
significant threat to the long-term survival of the species.
Drought
    In severe drought, as the region has experienced over the last 15 
years (TWDB 2006, 1-60, 1-67), the linear extent of dewatered riverine 
habitats could be large and the length of time without flows could 
extend for several months or more (Service 2004, p. 51). Decreased flow 
will likely reduce the amount of available shallow rocky habitats in 
much of the river. However, Concho water snakes appear able to survive 
these low flow periods. For example, Elm Creek had experienced a number 
of extended no flow periods over the 5 years prior to 2004 and then 
flooded in August 2004. In September 2004, Dixon (2004, p. 11) noted 
Concho water snakes inhabited the site. Dixon (2004, p. 12) surmised 
that snakes either moved from the mouth of Elm Creek at the Colorado 
River (a distance of 4.6 creek mi (7.4 creek km)), or existed in deep 
pools somewhere within a returnable distance to the site. Another 
example of snake persistence during dry times was the drying of 
Ballinger Lake in 2004 and confirmation of reproductive snakes in the 
lake in 2005 following rains (Dixon 2004, p. 4; Forstner et al. 2006, 
p. 15).
    According to Dixon (2004, p. 9), during long periods of drought, 
the low-head dams (small private dams, a few feet tall, that create 
pools upstream and riffle-like areas downstream) within both the Concho 
and Colorado Rivers form pools that can extend two-thirds of a mile (1 
km) or more up river (depending on dam height). The riffles and pools 
that lie upstream of these low-head dams may not completely dry up 
because of small springs and creeks nearby. These pools act as refuges 
for juvenile and adult Concho water snakes when flow ceases (Dixon 
2004, p. 9). Concho water snakes have been located in pools behind low-
head dams along the Colorado River, and Dixon (2004, p. 9) states that 
it is reasonable to expect the small pools behind low-head dams on the 
Concho River act in the same way. Even with the drought, water 
continues to flow over bedrock in some areas, and snakes have been 
observed foraging for fish in the diminished flow. The extent of solid 
bedrock in some of the riffle systems tends to maintain the nature of 
the riffle and does not allow vegetation to root and collect debris and 
silt (Dixon 2004, p. 9).
    Another way the snakes may endure drying conditions is to use deep 
burrows. Greene (1993, pp. 89, 94) found Concho water snake hibernacula 
(shelters for hibernating snakes) within 19.7 ft (6 m) of water with a 
mean depth of 1.7 ft (0.52 m). Hibernacula types included crayfish 
burrows, rock ledges, debris piles, and concrete low water crossings 
for adults and loose embankments of rock and soil for juveniles. Dixon 
(2006, p. 2) stated that during droughts the snakes were possibly in 
the crayfish burrows, since they may retain moisture.
    Even in light of the ongoing regional drought (TWDB 2006, pp. 1-60, 
1-67), USGS stream gauges have registered four flood events greater 
than 400 cubic feet per second (cfs) below Spence Reservoir and six 
flood events greater than 1,000 cfs below Ivie Reservoir over the last 
10 years. While both Dixon (2004, pp. 8-9) and Forstner et al. (2006, 
pp. 12, 15) document degradation of riffles from siltation, there are 
still numerous riffles continuing to support Concho water snakes (Dixon 
2004, pp. 5-8).
    The Concho water snake has evolved and adapted for thousands of 
years through many documented long-term droughts (Forstner et al. 2006, 
pp. 17-19). Forstner et al. (2006, pp. 16, 20) state that ``the impacts 
and future stressors on this taxon by anthropogenic and natural cycles 
are inevitable,'' and ``the snake has persisted in an environment for 
the past several millennia that has seen frighteningly intense periods 
of drought.'' Additionally, while there have never been minimum flows 
required for the Concho River below San Angelo, there

[[Page 38961]]

are several smaller dams ``up and down the Concho River, [which] act as 
refugia for Concho water snakes (Dixon 2004, p. 4).'' Therefore, 
because the snakes have survived under long-term drought and low-flow 
conditions (Forstner et al. 2006, p. 22), we believe that the threat 
from drought is not likely to endanger the Concho water snake in the 
foreseeable future.
Floodwater Scouring and Instream Flows
    As discussed above, at the time of listing, we believed the 
construction of Ivie Reservoir would curtail normal water flow and 
prevent floodwater scouring. Without such flooding, riffle habitat is 
lost as the rocky streambed becomes covered with silt. In their recent 
survey of the Concho water snake and its habitat, Forstner et al. 
(2006, pp. 14, 16) found that the lack of flushing flows has allowed 
silt to settle and cover many of the riffles at historically occupied 
sites and that several sites have changed from riffles to slow-flowing 
sandy sections of river, reducing habitat available to these snakes. 
Sand and silt fill in graveled cobble substrate and provide areas for 
growth of salt cedar and other vegetation, which further eliminates the 
rocky-bottomed riffle areas required by Concho water snakes (51 FR 
31419; Scott and Fitzgerald 1985, p. 13; Forstner et al. 2006, p. 15). 
However, despite some riffle habitat loss and the presence of other 
system stressors, Forstner et al. (2006, p. 18) noted that the Concho 
water snake persisted and continued to reproduce at the majority of the 
sites they visited. Thus, we believe that the loss of some riffle 
habitat does not threaten the Concho water snake.
    Since issuance of the 1986 Biological Opinion and associated 
minimum flow requirements, stream flows throughout the range of the 
Concho water snake have declined considerably (Forstner et al. 2006, 
pp. 13-16). According to the Regional Water Plan for Region F of the 
Texas Water Development Board (TWDB 2006, p. 1-6), ranching, irrigated 
agriculture, and the oil and gas industry have historically dominated 
the regional economy. The largest water user, about 66 percent of the 
total demand, is irrigated agriculture (provided mostly by groundwater 
pumping), and municipal is the next largest water user at almost 22 
percent (provided mostly by surface water reservoirs) (TWDB 2006, pp. 
1-19, 1-24). Based on an analysis of USGS stream gauges (Service 2004, 
p. 36), low flows in the rivers in recent years have been exacerbated 
by low annual rainfall totals throughout the watershed. Stream flows 
during 1999 to 2003 were substantially lower than the period of record 
for seven USGS stream gauges analyzed on the Colorado and Concho 
rivers. Recent flows on the Concho River, where minimum flows have not 
been required, have been particularly low. Prior to reservoir 
construction near the City of San Angelo, median annual flow on the 
Concho River at the San Angelo and Paint Rock gauges was 32 and 26 cfs, 
respectively, but declined to a median annual flow of 0.2 and 0.1 cfs, 
respectively, from 1999 to 2003. Discharges on the Colorado River have 
not ceased since 1986 due partly to minimum flows required by the 1986 
Biological Opinion on construction of Ivie Reservoir. However, median 
annual discharge prior to construction of Ivie Reservoir was 71 cfs and 
declined to 9 cfs between 1999 and 2003 (Service 2004, pp. 36-37).
    In July 2004, the USACE reinitiated formal consultation 
(Consultation Number 2-15-F-2004-0242) with the Service on the 
District's activities. Prior to completing the consultation, the 
District indicated through a letter (2004, pp. 1-2), and the USACE 
concurred via e-mail (2004, p. 1), that an emergency situation existed 
due to a limited water supply endangering public health and safety to 
their municipal customers (450,000 people). The ongoing drought and 
implementation of the conditions in the 1986 Biological Opinion were 
given as the basis for this emergency. During the emergency, the 
District was allowed to cease releasing minimum flows, while formal 
consultation was ongoing. An amended biological opinion (2004 
Biological Opinion) was completed in December 2004. Shortly thereafter, 
the District and the USACE determined the emergency had ended and the 
requirements of the amended Biological Opinion went into effect 
(Service 2004, pp. 1, 3). The main component of the 2004 Biological 
Opinion was a reduction in minimum flow requirements (Service 2004, pp. 
11-12). The new flow requirements included, to the extent there is 
inflow into Spence Reservoir, that the District will maintain a minimum 
flow in the Colorado River downstream of not less than 4.0 cfs (0.11 
cms) during April through September and 1.5 cfs (0.04 cms) during the 
months of October through March.
    While the reduced minimum flows outlined in the 2004 Biological 
Opinion will have an impact on the aquatic habitat conditions in the 
Colorado River, those impacts will be ameliorated to some degree by the 
nature of the intervening watersheds that drain each of these stream 
segments, since both the Colorado and Concho rivers are gaining streams 
(Service 2004, pp. 50-51). Gaining streams gather water as you progress 
downstream. This gathering of water is exhibited not only by tributary 
inflow but also as bank discharge from spring flow that occurs where 
shallow aquifers interface with the stream. This gaining stream 
phenomenon is greatly controlled by ambient weather conditions. During 
periods of long-term drought, the tributaries and springs will cease 
flowing; however, during normal rainfall periods, these sources of 
water help to restore and maintain more stable instream flows in the 
mainstem (Service 2004, p. 50). Additionally, even when releases from 
dams have ceased, normal seepage from a dam occurs and provides for the 
formation of pools (large and small) that can provide habitat for the 
Concho water snake and the fish it preys upon for varying periods of 
time depending on ambient weather conditions. When dam releases are 
resumed, the pools (located below dams and up and downstream from 
spring areas) that may have served as refugial habitat are reconnected 
by flowing water.
    If the Concho water snake is delisted, the minimum flow 
requirements required by the 2004 Biological Opinion will no longer 
apply. However, in February 2008 the Service entered into a MOU with 
the District to provide for the maintenance of these minimum flow 
releases in perpetuity. The purpose of the MOU is for the District to 
provide assurance that minimum reservoir releases will continue in 
perpetuity, consistent with the 2004 BO (Service, 2004, pp. 11-12). The 
releases will be maintained, to the extent there is inflow, if the 
Concho water snake is removed from the Federal list of threatened 
species. While this means the District has the authority to further 
reduce or even terminate flows during times of extremely low inflow, 
earlier analysis using 10 years of historical data indicated that, 
based on studies that demonstrate persistence of the snake in the past, 
such low flows occurring only occasionally and temporarily should not 
affect the snake's long-term status.
    The District has implemented every activity requested by the 
Service in previous biological opinions beginning in 1986. The minimum 
flows required in the 2004 Biological Opinion have been implemented by 
the District and those flow requirements were duplicated in the 2008 
MOU signed by the District. The District has an excellent track record 
of carrying out conservation actions to benefit the Concho water snake 
(Freese and Nichols 2006, Service pp. 42-47). The Service is

[[Page 38962]]

confident in the District's commitment and ability to carry out the 
provisions of the 2008 MOU to provide for minimum flows. Even in the 
absence of the MOU flow requirements, minimal amounts of water and 
stream flows will still be present at various times of the year in the 
gaining reaches of the Colorado River and below Spence and Ivie 
Reservoirs due to: dam leakage/seepage, inflow from creeks and other 
drainages, and spring activity.
    In addition to the MOU, and the 2004 Biological Opinion, Texas 
water law requirements also result in maintenance of instream flow. 
Texas observes traditional appropriative water rights, which is also 
known as the ``first in time, first in right'' rule (See Texas Water 
Code Sec.  11.027). The state's water policy requires the Texas 
Commission on Environmental Quality (TCEQ) to set, to the extent 
practicable, minimum instream flows to protect the state's water 
quality when issuing water rights permits (See Texas Water Code Sec.  
11.0235(c)). Furthermore, Texas water law prohibits the owner of stored 
water from interfering with water rights holders downstream or 
releasing water that will degrade the water flowing through the stream 
or stored downstream (Texas Water Code Sec.  297.93).
    The District's water rights permit (TCEQ permit 3676) 
requires the District to maintain flows below Ivie Reservoir of 8 cfs 
from April through September and 2.5 cfs from October through March. 
Flows must be maintained below both Spence and Ivie reservoirs to 
ensure water quality and provide for downstream water rights. Flows are 
mandated and releases from Spence Reservoir are periodically required 
by the State of Texas to ensure the quality of water entering Ivie 
Reservoir. Spence Reservoir is known to be high in dissolved solids and 
chlorides (Service 2004, p. 6), so if flows into Spence Reservoir are 
low, water quality in the reservoir can become degraded unless flushing 
flows are released. The District must also ensure that senior water 
right holders are delivered specific amounts of water from Ivie 
Reservoir. Therefore, long-term low flow releases or no releases from 
Spence and Ivie Reservoirs are rare.
    The District has been able to maintain flows from both Spence and 
Ivie reservoirs over the long term as evidenced by long-term measures 
of flows at two gages. Daily median flows in the reach of the Colorado 
River below Spence Reservoir (as measured at USGS near Ballinger since 
Spence Reservoir was constructed, 1969-2007) exceeded 4.0 cfs in the 
summer (April through September) all but 12 days. During the winter 
(October through March), daily median flows always exceeded 1.5 cfs. 
Daily median flows in the reach of the Colorado River below Ivie 
Reservoir (as measured at USGS at Winchell since Ivie Reservoir was 
constructed, 1990-2007) exceeded 8.0 cfs in the summer (April through 
September) all but 15 days. During the winter (October through March), 
daily median flows always exceeded 2.5 cfs. We believe that the 
District will continue to maintain instream flows in the foreseeable 
future.
    While instream flows have decreased, Concho water snakes have 
continued to be found throughout their range. In addition, as discussed 
above in the Drought section, Concho water snakes appear to be able to 
survive low flow situations. Therefore, because the snakes have 
survived under low-flow conditions, and because some minimal flows will 
persist throughout parts of the snake's range (Forstner et al. 2006, p. 
22) due to natural inflows and dam releases by the District, we believe 
that the Concho water snake is not threatened due to lack of instream 
flows in the foreseeable future.
Vegetation Encroachment
    Salt cedar (Tamarisk sp.) is a nonnative species that was 
introduced to the United States in the 1800s from southern Europe or 
the eastern Mediterranean region (DiTomaso 1998, p. 326). In the 
watersheds of the Spence and Ivie Reservoirs, these plants are abundant 
and have been reported to have greatly affected water quality and 
quantity because they consume large volumes of water and then transport 
salts from the water to the surfaces of their leaves. When the leaves 
are dropped in the fall, the salt is concentrated at the soil surface 
(Freese and Nichols 2006, p. 5.5; DiTomaso 1998, p. 334).
    In an effort to increase water yield and reduce salt concentrations 
in Spence and Ivie reservoirs, the District, in cooperation with the 
Texas Cooperative Extension, the Texas Department of Agriculture, the 
U.S. Department of Agriculture--Agricultural Research Service, and the 
Texas State Soil and Water Conservation Board (TSSWCB), has initiated a 
salt cedar control project in the Upper Colorado River Basin, which 
includes spraying an herbicide to eradicate mass concentrations of salt 
cedar and then using a leaf beetle for biological control of new plant 
growth (Freese and Nichols 2006, p. 6.4). This project ``is an 
excellent first step in the recovery of the Upper Colorado River Basin 
back to many of its [pre-infestation] functions, including native 
riparian habitat for wildlife and improved habitat for fish and other 
aquatic organisms,'' and is ``one of the most crucial options for 
improving water quality and quantity'' (Freese and Nichols 2006, pp. 
6.5-6.6). We have no information that the herbicide poses a direct 
poisoning threat to the Concho water snake.
    Additionally, control programs for invasive brush species, such as 
juniper (Juniperus sp.) and mesquite (Prosopis sp.), are also being 
implemented in the Concho and Upper Colorado River basins to increase 
water quantity (Freese and Nichols 2006, p. 6.6; TSSWCB 2004, pp. 2-3). 
The TSSWCB is currently focusing above O.C. Fisher and Twin Buttes 
reservoirs on the Concho River and to date over 175,000 acres (70,820 
hectares) of invasive brush have been treated in these watersheds 
(TSSWCB 2004, pp. 2-3). The removal and control of salt cedar and other 
invasive brush from the riparian reaches of the Colorado and Concho 
rivers helps augment existing stream discharge and also reduces buildup 
of dissolved solids (salts) in the soils of the riparian zone (Service 
2004, p. 56). Additionally, this removal encourages reformation of 
riffle areas, increases stream flow, and reduces sediment deposition, 
which improves instream habitat for the Concho water snake and other 
aquatic species (Freese and Nichols 2006, p. 6.6).
Fragmentation
    At the time of listing, we believed construction of Ivie Reservoir 
(formed by Freese Dam) would likely segment Concho water snakes into 
three separate populations and thereby reduce genetic exchange (Scott 
and Fitzgerald 1985, p. 34). Prior to the snake's listing in 1986, no 
researchers had documented Concho water snakes traveling over land to 
circumvent the barriers caused by large dams, and snakes had not been 
located in reservoirs. Due to this separation, a reasonable and prudent 
measure in the 1986 Biological Opinion was to transfer snakes annually 
between the populations separated by the dam. Snakes were transferred 
in 1995 and again in 2006 (District 1995, p. 1; District 2006, pp. 1-
3).
    Because we now know Ivie Reservoir, which receives flow from both 
the Concho and Colorado Rivers, to be occupied, we believe it is 
reasonable to surmise that snakes are capable of genetic interchange 
between the Concho and Colorado Rivers via the reservoirs' shorelines. 
The District (1998, p. 14) summarized Concho water snake habitat within 
Ivie Reservoir and found that

[[Page 38963]]

although the habitat is not linearly consistent, it does occur 
throughout the reservoir. Female Concho water snakes produce their 
first young at 2 or 3 years of age (Werler and Dixon 2000, p. 216). 
Based on occupancy of reservoirs and moderate generation time, we have 
a high level of confidence that gene flow occurs between populations.
    In recent surveys, Forstner et al. 2006 (pp. 10-13, 18) found that 
Concho water snakes were reproducing in the Concho and Colorado Rivers 
above Ivie Reservoir and in the Colorado River below it; they concluded 
that the populations in those three river reaches were self sustaining 
and seemingly viable (Forstner et al. 2006, pp. 16-18, 20). The 2008 
MOU (mentioned above), Article 4.1 also provides that, in the 
springtime, the District, in coordination with the Service, should move 
5 male snakes from below Spence and Freese dams to above these dams, 
once every 3 years. Moving snakes will be dependent upon availability 
of funding for the District. We believe this movement will benefit the 
snake by enhancing genetic exchange between the three populations. 
Should funding be unavailable in any particular snake-moving year, 
every effort will be made to move snakes in the succeeding year. Based 
on the available data, we do not believe the species is likely to 
become threatened or endangered in the foreseeable future due to 
genetic isolation.
Pollution and Water Quality
    At the time of listing, we believed buildup of algae in riffle 
areas reduced oxygen and nutrients available to populations of fish, 
the Concho water snake's primary food (51 FR 31419). We were also 
concerned that the inflow of nutrients into the Concho River in the San 
Angelo area, along with reduced dilution capability associated with 
lower flows, created large concentrations of algae in portions of the 
river (51 FR 31419). A summary of the 1987-1996 fish collections in the 
Colorado and Concho Rivers, included in the Service's 2004 Biological 
Opinion (Appendix A, pp. 68-69), suggested that fish populations have 
persisted despite the presence of algae. Also, no impacts to snakes 
have been observed or documented as a result of water quality 
conditions during the ongoing drought (Service 2004, p. 52). 
Additionally, according to Dixon (2006, p. 2), Concho water snakes have 
been documented to survive in captivity for as long as 12 months with a 
reduced food supply. Therefore, we no longer consider algal growth and 
nutrient enrichment to be significant threats to the snake's survival.
    The Concho water snake was listed as endangered by the State of 
Texas in 1984. In 2000, it was removed from the State's list of 
threatened species (TPWD 2000, p. 3) because TPWD no longer considered 
it likely to become endangered (64 FR 41903).
    The Texas State Legislature implemented the Texas Clean Rivers 
program in 1991. The District has actively participated in the program 
since that time and monitors surface water quality in the upper 
Colorado River basin, which includes the distribution of the Concho 
water snake above Freese Dam. The Lower Colorado River Authority (LCRA) 
has the responsibility for water quality monitoring below Freese Dam. 
Both of these entities have participated in the Clean Rivers Program 
since 1991 and have provided a proactive response for ensuring a high 
level of surface water quality in the Colorado River and its mainstem 
reservoirs. These programs are ongoing and designed to ensure water 
quality integrity for all aquatic resources, including the Concho water 
snake and fish, its primary food source, in the upper basin. As water 
quality problems are detected, swift responses by the District and LCRA 
to effect corrective actions through State of Texas regulatory agencies 
(TCEQ and the Texas Railroad Commission) are completed (Service 2004, 
pp. 52-53).
    Additional water quality protections for Concho water snakes in 
riverine and reservoir habitats will continue indirectly under the 
Clean Water Act (CWA). According to the Environmental Protection Agency 
(2006, p. 1), the CWA establishes basic structures for regulating 
discharges of pollutants into United States waters, protecting water 
quality for species dependent on rivers and streams for their survival.
    According to species experts, minimally maintained, ``mandated 
flows below Ivie Reservoir (TCEQ permit 3676) [and] senior 
water rights below both Spence and Ivie reservoirs'' will adequately 
provide instream flows for the Concho water snake (Forstner et al. 
2006, p 21), preventing the snake from likely becoming threatened or 
endangered in the foreseeable future because the snake has persisted 
under these conditions historically, including the ongoing drought, as 
discussed earlier in this proposal.
Forage Fish Availabilty
    At the time of listing, we believed that declining flows, 
inundation, pollution, and other habitat threats would have adverse 
impacts on riffle-dwelling fish, the principal food of the Concho water 
snake (Williams 1969, pp. 9-10; Dixon et al. 1988, p. 16; 1989, p. 8; 
1990, p. 36; 1992, p. 6; Greene et al. 1994, p. 167; Thornton 1990, p. 
14). While we do not know the full extent of the drought's effects on 
the local fish populations, we do have information that indicates the 
snake is able to survive in captivity for up to 12 months with a 
reduced food supply (Dixon 2006, p. 2), and based on the snake's 
persistence and reproduction within all three reaches (Forstner et al. 
2006, pp. 10-13, 18), we believe that the Concho water snake is no 
longer threatened with endangerment in the foreseeable future as a 
result of potential threats to local food fish populations.
Factor A Summary
    In conclusion, over the course of 20 years, including the 
construction of three dams that were anticipated to fragment the 
distribution of the Concho water snake, a prolonged drought accompanied 
by extreme low water flows in parts of the snake's range, and concerns 
about heavy nutrient inflows, surveys have confirmed that the snakes 
have occupied habitat along the new lakeshores, survived in or quickly 
reoccupied areas of extreme low flows, and have not been adversely 
affected by nutrient-related effects. Additionally, habitat restoration 
efforts such as the removal of salt cedar and other brushy species may 
be improving instream habitat for the Concho water snake and other 
aquatic species. We believe that destruction, modification, or 
curtailment of the Concho water snake habitat or range due to habitat 
loss, altered instream flows and floodwater scouring, drought, 
vegetation encroachment, fragmentation, and pollution no longer 
threaten the Concho water snake with becoming endangered.
    Forstner (2006 p. 12) cites Soule's 1987 definition that describes 
the key criteria for a viable population to include the ability of the 
population to be self sustaining, able to persist over time (a century 
or longer for the Concho water snake), and the ability to adapt to 
local conditions and evolutionary pressures. Forstner stated that the 
criteria of self sustaining, seemingly viable populations in the Concho 
and Colorado rivers at the end of a decade of monitoring have been met. 
Recalling the three recovery criteria from the 1993 Concho Water Snake 
Recovery Plan: Adequate instream flows, viable populations in each of 
the three major reaches (as indicated by not only the repeated presence 
of snakes at long-term monitoring sites, but by documented evidence of 
reproduction as a measure

[[Page 38964]]

of sustainability), and movement of water snakes to counteract 
population fragmentation. Forstner's 2006 Final Survey Assessment 
Report (May 18, 2006 p. 12) concludes that his assessment indicates 
that two out of three of the criteria have been met. Fortner (2006 p. 
13) then states that his assessment did not address the final instream 
flow criterion, yet concludes that ``in addition to the mandated flows 
below Ivie Reservoir (TCEQ permit 3676), senior water rights 
below both Spence and Ivie Reservoirs virtually assure maintenance of 
instream flows simply as a consequence of meeting those water right 
demands. The assurance of the instream flow criterion can be met 
without ever considering the flows agreed to by the District in the 
2008 MOU. The Service realizes that severe environmental conditions 
that reduced reservoir releases and instream flow have occurred in the 
past and will occur in the future, and we are confident that the 
District will continue to implement all appropriate conservation 
actions, including providing the flows outlined in the 2008 MOU. 
Furthermore, we believe that the District will continue to comply with 
its TCEQ water rights permit, which mandates flow releases from Ivie 
Reservoir. Since the listing of the Concho water snake in 1986, the 
District has an impeccable track record of providing flows, moving 
snakes, and facilitating/conducting research and monitoring to conserve 
the species.

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

    At the time of listing, Concho water snakes were known to sometimes 
be captured or killed by recreationists (51 FR 31420). The effect of 
this activity on Concho water snake populations was and still is 
believed to be minimal. However, instances of Concho and Brazos water 
snakes being killed have been reported in both populated and 
unpopulated areas. For example, Brazos water snakes have been crushed 
under stones at the water's edge by people walking on the banks and 
shot by small caliber firearms, and fishermen have commented on their 
success in removing the ``water moccasins'' from the river (Forstner et 
al. 2006, pp. 18-19). At one of the historically most productive 
localities for Brazos water snakes (a closely related species occurring 
in an adjacent drainage), Forstner et al. (2006, p. 18) found no snakes 
in 2 years of searching. They noted dozens to hundreds of campers at 
the site each year. According to Dixon (2006, p. 2), there is not as 
much recreation occurring on the Concho and Colorado Rivers, where the 
Concho water snake occurs, as there is on the Brazos River. We are 
unaware of any plans to increase recreational opportunities in the 
Colorado and Concho Rivers to increase recreational use. Therefore, we 
believe that impacts from recreationists will continue to be less in 
the foreseeable future in the areas occupied by Concho water snakes.
    While some limited killing of snakes is likely still occurring, 
there is no evidence indicating that these mortalities are affecting 
the species on a rangewide or population level. Therefore, we find that 
mortality from this factor is not likely to cause the species to become 
threatened or endangered in the foreseeable future.

C. Disease or Predation

    At the time of listing, no problems of disease or predation on 
Concho water snakes were known to exist (51 FR 31420). While currently 
no disease problems are known, predators on Concho water snakes have 
been identified. As is true for most snakes, predation is considered a 
major natural source of mortality for Concho water snakes (Werler and 
Dixon 2000, p. 215). Predators documented to prey on Concho water 
snakes include kingsnakes (Lampropeltis getula), coachwhip snakes 
(Masticophis flagellum), racers (Coluber constrictor), raccoons 
(Procyon lotor), and great blue herons (Ardea herodias) (Greene 1993, 
p. 102; Dixon et al. 1988, p. 18; Williams 1969, p. 15). Raptors such 
as hawks (Buteo spp.) and falcons (Falco sp p.) are also known to 
predate upon snakes (Steenhof and Kochert 1988, p. 42). Predatory fish 
include bass (Micropterus salmoides) and channel catfish (Ictaclurus 
punctatus) (McGrew 1963, pp. 178-179; Jordan and Arrington 2001, 158). 
Predation of Concho water snakes clearly is occurring; however, all of 
these predators are native to this region and the snakes have persisted 
in the face of such predation both historically and during the last 20 
years during periods of dam construction and drought. Thus, we believe 
that mortality from predation is not likely to cause them to become 
threatened or endangered in the foreseeable future.

D. The Inadequacy of Existing Regulatory Mechanisms

    Due to the Texas Clean Rivers program, other Texas water law 
requirements, and the 2008 MOU between the Fish and Wildlife Service 
and the ASACE, both discussed earlier under Factor A, we believe that 
inadequacy of existing regulatory mechanisms does not constitute an 
ongoing threat to the Concho water snake.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    We are unaware of any other natural or manmade factors affecting 
the continued existence of the Concho water snake at this time.

Conclusion of the Five-Factor Analysis

    As required by the Act, we considered the five potential threat 
factors to assess whether the Concho water snake is threatened or 
endangered throughout all or a significant portion of its range. When 
considering the listing status of the species, the first step in the 
analysis is to determine whether the species is in danger of extinction 
throughout all of its range. If this is the case, then the species is 
listed in its entirety. For instance, if the threats on a species are 
acting only on a portion of its range, but they are at such a large 
scale that they place the entire species in danger of extinction, we 
would list the entire species.
    Since the time of listing, it has been shown that: (1) Concho water 
snakes can survive lower flows than previously thought necessary for 
their survival; (2) mandated flows, downstream senior water rights, and 
the 2008 MOU between the District and the Service virtually assure 
maintenance of adequate instream flows; (3) viable populations of 
Concho water snakes exist in all three reaches of the species' range; 
(4) the snake uses the shoreline of reservoirs; (5) snakes may not need 
to be transferred between populations in order to prevent genetic 
isolation, although the 2008 MOU provides for them to be moved; and (6) 
it persists, reproduces, and remains viable throughout its range. In 
addition, the removal of salt cedar and other invasive brushy species 
is restoring riparian habitat, small riffles, and water quality for the 
Concho water snake.

Application of the Results of the Five Factor Analysis to the Recovery 
Plan's Criteria

    The 1993 Recovery Plan described maintenance of adequate instream 
flows (Recovery Criterion 1) to maintain both the quantity and quality 
of Concho water snake habitat so that occupied habitat would continue 
to support viable po