[Federal Register: August 2, 1999 (Volume 64, Number 147)]
[Proposed Rules]               
[Page 41903-41905]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; Notice of 90-Day 
Finding on Petition To Delist the Concho Water Snake

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 90-day petition finding.


SUMMARY: We, the Fish and Wildlife Service (Service) announce a 90-day 
finding for a petition to delist the Concho water snake (Nerodia 
paucimaculata) under the Endangered Species Act of 1973, as amended. We 
find that the petitioner did not present substantial information 
indicating that delisting this species may be warranted.

DATES: The finding announced in this document was made on July 13, 

ADDRESSES: Comments, material, information, or questions should be sent 
to the Supervisor, U.S. Fish and Wildlife Service, Ecological Services, 
10711 Burnet Road, Suite 200, Austin, Texas 78758. The petition and 
supporting data are available for public inspection by appointment 
during normal business hours at the above address. A copy of the 
finding announced in this notice may be obtained by writing to the 
above address.

FOR FURTHER INFORMATION CONTACT: Patrick Connor, Fish & Wildlife 
Biologist, at the above address (telephone 512-490-0057 ext. 227).



    Section 4(b)(3)(A) of the Endangered Species Act of 1973, as 
amended (16 U.S.C. 1531 et seq.) (Act), requires that we make a finding 
on whether a petition to list, delist, or reclassify a species presents 
substantial scientific or commercial information to demonstrate that 
the petitioned action may be warranted. To the maximum extent 
practicable, we must make this finding within 90 days of the date the 
petition is received, and this finding must be published promptly in 
the Federal Register. If the finding is that the petitioner has 
presented substantial information we must then promptly commence a 
status review of the species.
    When evaluating whether the substantial information standard is 
met, we use the definition provided in the implementing regulations at 
50 CFR 424.14(b). Substantial information is defined as ``that amount 
of information that would lead a reasonable person to believe that the 
measure proposed in the petition may be warranted.'' The factors for 
listing, delisting or reclassifying species are described in 50 CFR 
424.11. We may delist a species only if the best scientific and 
commercial data available substantiate that it is neither endangered 
nor threatened. Delisting may be based on one of the following 
reasons--(1) extinction, (2) recovery, or (3) original data for 
classification were in error.
    On June 29, 1998, we received a petition by John W. Grant on behalf 
of the Colorado River Municipal Water District (CRMWD) dated June 24, 
1998, to delist the Concho water snake (CRMWD 1998). The petition 
asserts that--(1) the status of the Concho water snake was stable at 
the time of listing and continues to be stable, (2) all putative 
threats are insubstantial, and (3) the determination that the Service 
made to list the snake as threatened was in error. After careful 
review, we find that the snake should remain classified as threatened 
under the Act.
    The Concho water snake is endemic to the Concho and Colorado rivers 
in Runnels, Tom Green, Concho, McCulloch, Coleman, Brown, Mills, San 
Saba, Irion, Lampasas, and Coke counties, Texas. We listed the Concho 
water snake as threatened on September 3, 1986, due in part, to its 
limited geographic range, limited population sizes, and loss of 
important habitats and prey base resulting from water development 
projects (past, ongoing, and future) (51 FR 31412). We designated 
critical habitat for the species on June 29, 1989 (54 FR 27377).

[[Page 41904]]

    Information presented in the petition indicates that, in the 15 
areas monitored by CRMWD and in certain reaches of O.H. Ivie 
Reservoir's shoreline, Concho water snake populations persist. The 
voluminous data on the snake and its fish preybase submitted by the 
petitioner provides a detailed picture of snake's status at the CRMWD 
and Texas A&M University monitoring sites. However, as discussed in the 
petition, due to limitations in site visits and resultant low number of 
recaptures, CRMWD biologist were unable to make precise local Concho 
water snake population size estimates.
    The current range of the Concho water snake is similar to when the 
species was listed 13 years ago. The snake's primary habitat remains 
riverine (located on or inhabiting the bank of a river). This habitat 
is threatened by inadequate instream flows to support the fish preybase 
for the snake. Each of the three major riverine sections (Concho River, 
Colorado River from Spence Reservoir to O.H. Ivie Reservoir, and 
Colorado River downstream of O.H. Ivie Reservoir) of the snake's range 
are downstream of reservoirs. Operations at these reservoirs (O.C. 
Fisher, Lake Nasworthy, Twin Buttes, E.V. Spence, and O.H. Ivie) can 
affect instream flows for snakes and their prey for significant periods 
of time.
    In a biological opinion for the U.S. Army Corps of Engineers we 
identified instream flows (including flushing flows for channel 
maintenance) below Spence and Ivie reservoirs in our reasonable and 
prudent alternatives. If we delist the Concho water snake, the 
requirements of the biological opinion would no longer be in effect.
    CRMWD biologists made multiple preybase surveys using seines at the 
15 required monitoring sites, as well as other sites. The small fishes 
in these surveys, upon which snakes are known to feed, are variable in 
numbers from year to year but generally do not appear to have been a 
limiting factor for local populations during this period. However, if 
instream flows are inadequate there will be a decrease in Concho water 
snake prey.
    We do not agree with statements made in the petition that 
reductions in stream flow are not (and will not be) a problem. Low flow 
conditions exacerbate any significant pollution problems (i.e. 
increases in nutrients and/or toxic compounds). If those conditions 
persist long enough (perhaps for as little as three years), water 
snakes in those reaches will be at risk of extirpation. The demise of 
the Concho water snake population below E.V. Spence Reservoir following 
its construction is likely related to inadequate instream flows 
(reservoir releases). Scott et al. (1989) found certain reaches of the 
Colorado River ``too dry for too long to support water snake 
    Since the early 1930s, at least five major droughts occurred State-
wide in Texas lasting multiple years and disrupting normal use of the 
State's water resources (U.S. Geological Service 1991). An inadequate 
instream flow regime remains one of the most serious threats to the 
snake due to the prevalence of droughts in Texas.
    According to information presented in the petition, in the years 
following the inundation of riverine habitat by O.H. Ivie Reservoir, 
Concho water snakes survived and reproduced in the reservoir. However, 
blockage to Concho water snake movement by Freese Dam and the 
discontinuous nature of some of the reservoir habitat remain as 
potential barriers to gene flow between populations. In addition, 
available information does not enable precise estimates on the size or 
health of the snake population on O.H. Ivie Reservoir. Despite 
indications that Concho water snakes have been able to survive for a 
decade, the mid-term and long-term fate of the Concho water snake in 
O.H. Ivie Reservoir remains uncertain. Examination of the data 
presented suggests that the abundance of snakes is variable among 
reservoirs and in general less than the abundance of snakes in suitable 
riverine habitat. Information presented and available to us indicates 
that habitat loss from water development and diversion projects remains 
a threat.
    The information presented in the petition indicates that, at least 
in the early successional stages of O.H. Ivie Reservoir, snakes have 
been able to survive. However, in the course of the life of reservoirs 
such as O.H. Ivie, sediment will deposit in the upper reaches of the 
reservoir. Over time and depending on various conditions in the 
watershed, upper O.H. Ivie will likely become less suitable snake 
habitat. Furthermore, changes to the reservoir's fishery due to 
stockings of game fish and degradation of cover and structure may 
adversely affect Concho water snake prey availability. While Concho 
water snakes are somewhat flexible in their response to changes in prey 
items, an event that would result in the reduction of preferred size 
food items (e.g, small minnows for juvenile snakes) could affect the 
species' ability to sustain current population levels. If such an event 
lasted multiple years, we would expect the snake population to decline. 
Recruitment would be reduced and populations would decline.
    Another factor that threatens the Concho water snake is the 
fragmentation and isolation of populations resulting from habitat 
disturbance and from physical barriers such as the Freese Dam. The 
petition discusses fragmentation citing the Concho water snake genetics 
study of Sites and Densmore (1991). There is general agreement on 
several issues--(1) the distribution of the Concho water snake is a 
linear array of demes (a series of local populations) connected with 
occasional gene flow and associated with specific habitat features such 
as riffles (a section of a river characterized by swifter currents, 
shallow depths and broken water with turbulence or waves at the 
surface); (2) the Freese Dam poses a barrier to water snake movement 
both upstream and downstream; (3) mitigation against fragmented 
habitats and conservation of the Concho water snake require the 
artificial movement of Concho water snakes between (a) the Colorado 
River below Freese Dam and the Concho River and (b) the Colorado River 
below Freese Dam and the Colorado River above Ivie Reservoir; and (4) 
water snakes (Nerodia spp.) in general and Concho water snakes 
specifically have very low levels of genetic variation.
    The petition states that the Ivie Reservoir population effectively 
connects the Concho and upper Colorado River populations. However, two 
issues remain that indicate the reservoir itself may be a barrier--(1) 
the current discontinuity of habitat patches along the reservoir 
shoreline along with the variability with which Concho water snakes 
occupy those patches and (2) more importantly, the ultimate fate of (a) 
the reservoir's physical habitats in the upper reaches and (b) the 
Concho water snake reservoir populations.
    One significant point not addressed by the petition is the wide 
variability in the health of Concho water snake reservoir populations. 
Concho water snakes are probably absent from the lakes of the San 
Angelo area. Available information dating to Martin Whiting's thesis 
(1993) indicates that the Spence Reservoir population is limited with 
probably less than 200 individual snakes total (n < 200 total) for his 
two study sites. Additionally, Whiting found no evidence that the two 
Spence Concho water snake populations (Pecan Creek and Pump Station 
populations) exchanged individuals even though they were in the same 
general area of the reservoir separated by about 2,000 meters (m) or 
(6,562 feet (ft)).

[[Page 41905]]

    The likelihood of survival of Concho water snakes in specific 
reservoirs is likely to be dependent upon a variety of factors such 
as--(1) reservoir hydrology (inflows to and outflows/diversions from 
the lake); (2) the time scale chosen (changes to water snake habitats 
found along the shoreline and the shallow parts of a lake may occur 
over several decades as opposed to years); limnology (study of 
freshwater systems such as lakes ponds and rivers and their plant and 
animal communities as they are affected by their physical, chemical, 
and biotic environment); and (4) continuity and connectivity with other 
Concho water snake populations. The persistence of the Concho water 
snake in Spence Reservoir does not assure us that the snake will 
persist in Ivie Reservoir. The two reservoirs differ in their 
hydrology, and we believe more data are needed to understand the fate 
of the Concho water snake in Ivie Reservoir area.


    In addition to the analysis discussed above, we evaluated the 
petition in the context of the snake's recovery criteria as set forth 
in the species' recovery plan (Service 1993). We will consider the 
Concho water snake for delisting when--(1) Adequate instream flows are 
assured; (2) viable populations are present in each of the three major 
reaches * * *; and (3) movement of an adequate number of snakes is 
assured to counteract the adverse effects of population fragmentation. 
Importantly, the petition does not address criterion one. In regards to 
criterion two, while Concho water snake population in each of the three 
major reaches are stable, there is no reliable data available to 
indicate that these populations remain viable. Viable populations are 
self-sustaining and can persist for the long-term (Soule 1987).
    We believe the information provided by the petitioner has added to 
our knowledge of the distribution and abundance of the Concho water 
snake. However, the petition lacks adequate information upon which to 
evaluate the long-term viability of individual populations. Further 
investigations are needed to understand the various factors important 
to the snake's long-term viability, including range wide monitoring, 
and the future distribution of habitat patches, whether occupied and 
unoccupied, including those at the O.H. Ivie Reservoir.
    In summary, the petition fails to provide information indicating 
that any of the three criteria for delisting (from the recovery plan) 
are met. Further, the impact of declining instream flows (due to 
drought and/or water diversions), long term changes to lake habitats, 
pollution, and other habitat threats on the riffle-dwelling fish in the 
Concho and Colorado rivers are not addressed in the petition.

References Cited

Colorado River Municipal Water District. 1998. Petition to delist 
the Concho water snake. Submitted to United States Department of the 
Interior and Texas Parks and Wildlife Department. pp. 33 + 
appendices a-c.
Scott, N.J., Jr., T.C. Maxwell, O. W. Thornton, Jr., L.A. 
Fitzgerald, and J.W. Flury. 1989. Distribution, habitat, and future 
of Harter's water snake, Nerodia harteri, in Texas. Journal of 
Herpetology 23(4): 373-389.
Soule, M.E. 1987. Introduction. In: Viable Populations for 
Conservation. M.E. Soule, editor. Cambridge Univ. Press. New York. 
189 pp.
U.S. Fish and Wildlife Service. 1993. Concho Water Snake Recovery 
Plan. Albuquerque, New Mexico vii+66 pp.
Whiting, M.J. 1993. Population ecology of the Concho water snake, 
Nerodia harteri paucimaculata, in artificial habitats. Unpublished 
M.S. thesis. Texas A&M University. xvi+137 pp.

    Author: The author of this document is Patrick Connor, Austin 
Ecological Services Field Office (see ADDRESSES section).


    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: July 13, 1999.
John G. Rogers,
Acting Director, Fish and Wildlife Service.
[FR Doc. 99-19711 Filed 7-30-99; 8:45 am]