[Federal Register Volume 62, Number 243 (Thursday, December 18, 1997)]
[Rules and Regulations]
[Pages 66295-66304]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-33041]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AD28


Endangered and Threatened Wildlife and Plants; Final Rule To List 
Three Aquatic Invertebrates in Comal and Hays Counties, TX, as 
Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: The Fish and Wildlife Service (Service) determines three 
aquatic invertebrate species known only from Comal and Hays counties, 
Texas, to be endangered species under the Endangered Species Act of 
1973, as amended (Act). The invertebrates to be listed are Peck's cave 
amphipod (Stygobromus pecki), Comal Springs riffle beetle (Heterelmis 
comalensis), and Comal Springs dryopid beetle (Stygoparnus comalensis). 
The primary threat to these species is a decrease in water quantity and 
quality as a result of water withdrawal and other human activities 
throughout the San Antonio segment of the Edwards Aquifer. This action 
implements Federal protection provided by the Act for these three 
invertebrates.

EFFECTIVE DATE: January 20, 1998.

ADDRESSES: The complete file for this rule is available for inspection, 
by appointment, during normal business hours at the Ecological Services 
Field Office, U.S. Fish and Wildlife Service, 10711 Burnet Road, Suite 
200, Austin, Texas 78758.

FOR FURTHER INFORMATION CONTACT: Ruth Stanford, Ecologist (see 
ADDRESSES section) (512/490-0057; facsimile (512/490-0974).

SUPPLEMENTARY INFORMATION:

Background

    The Service designates Peck's cave amphipod (Stygobromus pecki), 
Comal Springs riffle beetle (Heterelmis comalensis), and Comal Springs 
dryopid beetle (Stygoparnus comalensis) as endangered under the 
authority of the Act (16 U.S.C. 1531 et seq.). These three aquatic 
invertebrate species are restricted in distribution to spring sites in 
Comal and Hays counties, Texas, and in the case of Peck's cave amphipod 
and Comal Springs dryopid beetle, the associated aquifer. Peck's cave 
amphipod is known from Comal Springs and Hueco Springs, both in Comal 
County. The Comal Springs riffle beetle is known from Comal Springs and 
San Marcos Springs (Hays County). The Comal Springs dryopid beetle is 
known from Comal Springs and Fern Bank Springs (Hays County).
    The water flowing out of each of these spring orifices comes from 
the Edwards Aquifer (Balcones Fault Zone--San Antonio Region), which 
extends from Hays County west to Kinney County. Comal Springs are 
located in Landa Park, which is owned and operated by the City of New 
Braunfels, and on private property adjacent to Landa Park. Hueco 
Springs and Fern Bank Springs are located on private property. The San 
Marcos Springs are located on the property of Southwest Texas State 
University.

[[Page 66296]]

    Peck's cave amphipod is a subterranean, aquatic crustacean in the 
family Crangonyctidae. The Comal Springs riffle beetle is an aquatic, 
surface-dwelling species in the family Elmidae. The Comal Springs 
dryopid beetle is the only known subterranean member of the beetle 
family Dryopidae. Elmid and dryopid beetles live primarily in flowing, 
uncontaminated waters.
    The first recorded specimen of the amphipod Stygobromus 
(=Stygonectes) pecki (Holsinger 1967) was collected by Peck at Comal 
Springs in June 1964. Reddell collected a second specimen at the same 
place in May 1965. In 1967, Holsinger named the species Stygonectes 
pecki, in Peck's honor, selecting the 1965 specimen as the type 
specimen. Later he included all the nominal Stygonectes species in the 
synonymy of the large genus Stygobromus. The Service has used ``cave 
amphipod'' as a generic common name for members of this genus, and this 
name was simply transliterated as ``Peck's cave amphipod'' without 
reference to a particular cave.
    Over 300 specimens of Peck's cave amphipod have been collected 
since its description. Most specimens were netted from crevices in rock 
and gravel near the three largest orifices of Comal Springs on the west 
side of Landa Park in Comal County, Texas (Arsuffi 1993, Barr 1993). 
Barr collected one specimen from a fourth Comal spring run on private 
property adjacent to Landa Park and one specimen from Hueco Springs, 
about 7 kilometers (km) (4 miles (mi)) north of Comal Springs (Barr 
1993). Despite extensive collecting efforts, no specimens have been 
found in other areas of the Edwards Aquifer.
    Like all members of the exclusively subterranean genus Stygobromus, 
this species is eyeless and unpigmented, indicating that its primary 
habitat is a zone of permanent darkness in the underground aquifer 
feeding the springs. Above ground, individuals are easy prey for 
predators, but they usually take shelter in the rock and gravel 
crevices and may succeed in reentering the spring orifice. Barr (1993) 
got most specimens in drift nets at spring orifices and found them less 
often as she moved downstream, supporting the notion that they may be 
easy prey and do not likely survive for long outside the aquifer.
    The Comal Springs riffle beetle is a small, aquatic beetle known 
from Comal Springs and San Marcos Springs. It was first collected by 
Bosse in 1976 and was described in 1988 by Bosse et al. The closest 
relative of H. comalensis appears to be H. glabra, a species that 
occurs farther to the west in the Big Bend region (Bosse et al. 1988).
    Adult Comal Springs riffle beetles are about 2 millimeters (mm) 
(\1/8\ inch (in)) long, with females slightly larger than males. Unlike 
the other two organisms listed here, the Comal Springs riffle beetle is 
not a subterranean species. It occurs in the gravel substrate and 
shallow riffles in spring runs. Some riffle beetle species can fly 
(Brown 1987), but the hind wings of H. comalensis are short and almost 
certainly non-functional, making the species incapable of this mode of 
dispersal (Bosse et al. 1988).
    Larvae have been collected with adults in the gravel substrate of 
the spring headwaters and not on submerged wood as is typical of most 
Heterelmis species (Brown and Barr 1988). Usual water depth in occupied 
habitat is 2 to 10 centimeters (cm)(1 to 4 in) although the beetle may 
also occur in slightly deeper areas within the spring runs. Populations 
are reported to reach their greatest densities from February to April 
(Bosse et al. 1988). The Comal Springs riffle beetle has been collected 
from spring runs 1, 2, and 3 at Comal Springs in Landa Park (springs j, 
k, and l in Brune 1981) and a single specimen was collected from San 
Marcos Springs 32 km (20 mi) to the northeast.
    The Comal Springs dryopid beetle is a recently discovered species. 
It was first collected in 1987 and described as a new genus and species 
in 1992 by Barr (California State University) and Spangler (National 
Museum of Natural History, Smithsonian Institution). Adult Comal 
Springs dryopid beetles are about 3.0-3.7 mm (\1/8\ inch) long. They 
have vestigial (non-functional) eyes, are weakly pigmented, 
translucent, and thin-skinned. This species is the first subterranean 
aquatic member of its family to be discovered (Brown and Barr 1988; 
Barr, in litt. 1990; Barr and Spangler 1992).
    Collection records for the Comal Springs dryopid beetle are 
primarily from spring run 2 at Comal Springs, but they have also been 
collected from runs 3 and 4 at Comal and from Fern Bank Springs about 
32 km (20 mi) to the northeast in Hays County. Collections have been 
from April through August. Most of the specimens have been taken from 
drift nets or from inside the spring orifices. Although the larvae of 
the Comal Springs dryopid beetle have been collected in drift nets 
positioned over the spring openings, they are presumed to be associated 
with air-filled voids inside the spring orifices since all other known 
dryopid beetle larvae are terrestrial. Unlike Peck's cave amphipod, the 
Comal Springs dryopid beetle does not swim, and it may have a smaller 
range within the aquifer.
    The exact depth and subterranean extent of the ranges of the two 
subterranean species (Comal Springs dryopid beetle and Peck's cave 
amphipod) are not precisely known because of a lack of methodologies 
available for studying karst aquifer systems and the organisms that 
inhabit such systems. Presumably an interconnected area, the 
subterranean portion of this habitat, provides for feeding, growth, 
survival, and reproduction of the Comal Springs dryopid beetle and 
Peck's cave amphipod. However, no specimens of these species have 
appeared in collections from 22 artesian and pumped wells flowing from 
the Edwards Aquifer (Barr 1993) suggesting that these species may be 
confined to small areas surrounding the spring openings and are not 
distributed throughout the aquifer. Barr (1993) also surveyed nine 
springs in Bexar, Comal, and Hays counties considered most likely to 
provide habitat for endemic invertebrates and found Stygoparnus 
comalensis only at Comal and Fern Bank springs and Stygobromus pecki 
only at Comal and Hueco springs.
    Although these species are fully aquatic and two of the three 
require flowing water for respiration, the absolute low water limits 
for survival are not known. They survived the drought of the middle 
1950's, which resulted in cessation of flow at Comal Springs from June 
13 through November 3, 1956. Hueco Springs is documented to have gone 
dry in the past (Brune 1981, Barr 1993) and, although no information is 
available for Fern Bank Springs, given its higher elevation, it has 
probably gone dry as well (Glenn Longley, Edwards Aquifer Research and 
Data Center, personal communication, 1993). San Marcos Springs has not 
gone dry in recorded history.
    These invertebrates were not extirpated by the only recorded 
temporary cessation of spring flow. However, given that they are fully 
aquatic and that no water was present in the springs for a period of 
several months, they were probably negatively impacted. These species 
are not likely adapted to surviving long periods of drying (up to 
several years in duration) that may occur in the absence of a water 
management plan for the Edwards Aquifer that accommodates the needs of 
these invertebrates. Stagnation of water may be a limiting condition, 
particularly for the Comal Springs dryopid beetle and Peck's cave 
amphipod.

[[Page 66297]]

    Stagnation of water and/or drying within the spring runs and the 
photic (lighted) zone of the spring orifices would probably be limiting 
for the Comal Springs riffle beetle because natural water flow is 
considered important to the respiration and therefore survival of this 
invertebrate species. Elmid and dryopid beetles have a mass of tiny, 
hydrophobic (unwettable) hairs on their underside where they maintain a 
thin bubble of air through which gas exchange occurs (Chapman 1982). 
This method of respiration loses its effectiveness as the level of 
dissolved oxygen in the water decreases. A number of aquatic insects 
that use dissolved oxygen rely on flowing water to obtain oxygen.

Previous Federal Action

    In a petition dated September 9, 1974, the Conservation Committee 
of the National Speleological Society requested the Service to list 
Stygobromus (=Stygonectes) pecki. The species was included in a notice 
of review published on April 28, 1975 (40 FR 18476). A ``warranted but 
precluded'' finding regarding several species in that petition was made 
on October 12, 1983, and published on January 20, 1984 (49 FR 2485). A 
warranted but precluded finding means that available information 
indicates listing the species as threatened or endangered is 
appropriate but that the listing is precluded by higher priority 
actions. The same determination has been repeated for Peck's cave 
amphipod in subsequent years. The species was included as a category 2 
candidate in comprehensive notices of review published on May 22, 1984 
(49 FR 21664), January 6, 1989 (54 FR 554), and November 21, 1991 (56 
FR 58804). Category 2 candidates were those species for which data in 
the Service's possession indicated that listing was possibly 
appropriate, but for which substantial data on biological vulnerability 
and threats were not known or on file to support proposed rules. 
Stygobromus pecki was elevated to category 1 status in the 1994 notice 
of review (59 FR 58982). Category 1 candidates were those species for 
which the Service had on file substantial information on biological 
vulnerability and threats to support a proposal to list. As published 
in the Federal Register on February 28, 1996 (61 FR 7596), candidate 
category 2 status was discontinued and only category 1 species are 
currently recognized as candidates for listing purposes.
    In a petition dated June 20, 1990, and received June 21, 1990, Mr. 
David Whatley, then Director of the City of New Braunfels Parks and 
Recreation Department, requested that the Service list five 
invertebrate taxa, including Peck's cave amphipod and four insects. The 
Service treated this as a second petition for the amphipod. A notice of 
finding published April 29, 1991 (56 FR 19632), announced that the 
petition presented substantial information and that listing the Comal 
Springs riffle beetle and the Comal Springs dryopid beetle may be 
warranted. Formal status review was initiated for those species. Both 
species became candidates for listing in the 1994 notice of review (59 
FR 58982).
    Peck's cave amphipod, Comal Springs riffle beetle, and Comal 
Springs dryopid beetle were proposed for listing on June 5, 1995 (60 FR 
29537). The Act requires that a final determination on a proposed 
listing be made within one year of the proposal. However, a 
congressionally-imposed moratorium on final listing actions combined 
with a recision of funding for the Service's listing program prohibited 
timely publication of this final rule.

Summary of Comments and Recommendations

    In the June 5, 1995, proposed rule (60 FR 29537) and associated 
Federal Register notices all interested parties were requested to 
submit factual reports or information to be considered in making a 
final listing determination. Appropriate Federal and State agencies, 
local governments, scientific organizations, and other interested 
parties were contacted and requested to comment.
    A public hearing request came from Mr. David Langford, Executive 
Vice President of the Texas Wildlife Association, by letter dated June 
22, 1995. The hearing was held on July 24, 1995 at the New Braunfels 
Civic Center in New Braunfels, Texas. Legal notices of the public 
hearing, which invited general public comment, were published in The 
New Braunfels Herald-Zeitung, the San Marcos Daily Record, the Uvalde 
Leader-News, the Medina Valley-Times, and the San Antonio Express-News. 
Sixteen people attended the public hearing and one person provided oral 
testimony.
    The Service received 1 oral and 24 written comments on the 
proposal. Of the letters and oral testimony received, nine supported 
the proposed action, seven opposed it, and nine did not clearly state 
support or opposition.
    The Service solicited formal scientific peer review of the proposal 
from six professional biologists during the public comment period and 
received comments from two reviewers. Their comments are either 
incorporated into this listing decision as appropriate, or are 
addressed below.
    Written and oral comments presented at the public hearing and 
received during the comment period were incorporated into this final 
rule where appropriate. Comments not incorporated are addressed in the 
following summary. Comments of a similar nature or point are grouped 
and summarized. Where differing viewpoints around a similar issue were 
made, the Service has briefly summarized the general issue.
    Comment 1: Threats to the species are greatly exaggerated and 
inconsistent with available data. No real or immediate threat exists 
that would justify listing these invertebrates.
    Service Response: The primary threat to these species is loss of 
water in their habitat at Comal Springs and other springs where they 
occur. This threat is discussed in detail in Factor A of this rule.
    Comment 2: Samples of all three of the species were collected after 
the springs had ceased flowing in the immediately preceding years.
    Service Response: Spring flow did not cease from all outlets in 
1990, and only spring run 1 at Comal saw significant loss of water. 
During brief periods of very low spring flow the spring runs probably 
retain sufficient subsurface moisture to allow the Comal springs riffle 
beetle to survive. Furthermore, when periods of low spring flow are 
brief and the spring runs are not completely dry, the subsurface water 
level likely remains higher and closer to the spring openings. These 
conditions may allow the survival of these species, whereas a period of 
extensive, long-term cessation of spring flow likely would not. Because 
these invertebrates are fully aquatic and require relatively well-
oxygenated water, a reduction or cessation of spring flows, even if 
standing water remains around the spring orifices, may negatively 
impact the species. Loss of water entirely, within their habitat, would 
result in the extirpation of these aquatic species.
    Comment 3: It was noted that the Edwards Aquifer Authority 
(Authority) was created by S.B. 1477 to regulate withdrawal of water 
from the aquifer. The Authority withstood legal challenges with the 
passage of H.B. 3189, which was passed with the cooperation and 
guidance of the Department of Justice and implementation is 
anticipated. The commenter further stated that implementation of S.B. 
1477 and H.B. 3189 will regulate water withdrawal,

[[Page 66298]]

thus eliminating the primary threat, and the need to list the species.
    Service Response: Some of the legal issues regarding the 
establishment of the Authority have been resolved since the time the 
proposed rule was published and the elected board is in effect at this 
time. However, an aquifer management plan that would provide for 
protection of these species and their habitat is not yet in place. 
Further progress of this board could be beneficial in the future and, 
if threats are reduced or removed, could result in downlisting or, 
possibly, delisting the species.
    Comment 4: The City of New Braunfels has obtained surface water to 
meet base demand which will eliminate pumping in the immediate area of 
the springs and substantially diminish threats to the species.
    Service Response: As discussed in Factor A, all of the springs 
where these species occur are affected by water withdrawal throughout 
the aquifer's artesian zone to the west. Therefore, a management plan 
for the entire aquifer, not just the area near the springs, is 
necessary to moderate threats to the species.
    Comment 5: Service treatment of this complex and dynamic issue is 
incomplete and erroneous. The Service ignores Texas Natural Resources 
Conservation Commission (TNRCC) rules and proposed amendments to 
address water quality.
    Service Response: The Service acknowledges the extreme complexity 
of issues regarding the quality and quantity of water in the Edwards 
Aquifer. The TNRCC rules deal primarily with water quality issues. The 
more significant issue, however, is maintaining adequate spring flows 
and the likelihood that a water management plan will be in effect in 
the foreseeable future that will provide protection for these 
invertebrates, as discussed in Factor A.
    Comment 6: If currently listed species are provided adequate spring 
flow, then species that have survived previous cessation of spring flow 
will receive adequate protection without the need to list.
    Service Response: While there are species within the Comal and San 
Marcos ecosystems that are presently listed as threatened or 
endangered, none of these listed species are assured adequate spring 
flow. Furthermore, some of the techniques, such as spring flow 
augmentation, under consideration by some for providing spring flow, 
will not adequately provide for the invertebrates addressed in this 
final rule. For example, the Comal Springs riffle beetle occurs in the 
spring runs. If water is ``augmented'' into this area after the springs 
cease flowing, the spring orifices will act as recharge features. The 
water would return to the aquifer rather than remaining in the spring 
runs. In addition, if augmentation is attempted through subsurface 
modifications of the aquifer, the habitat of the two subterranean 
species could be negatively impacted.
    Comment 7: In 1991, the Service reported that these invertebrates 
were endemic to Comal Springs. Now each of the invertebrates is known 
from one other spring and each is known from all of the upper springs 
at Comal. This establishes a potentially wide range for the species. 
The subterranean habits of two of the species and the fact that they 
are found at springs as much as 20 miles apart suggests a much wider 
distribution in the aquifer that would obviate the need to list them as 
endangered.
    Service Response: Status surveys that were conducted for each of 
these species following the petition to list them found only one new 
location for each species. Locations in more than one spring run at 
Comal Springs is not surprising given the proximity of the spring runs. 
As stated previously, extensive surveys for the species at springs 
throughout Bexar, Comal, and Hays counties and examination of numerous 
well samples have found each of the species at Comal Springs and in 
very low numbers at one additional spring system each. The species were 
not found at most of the locations surveyed.
    Disjunct distributions (e.g., those that are separated by 20 miles) 
are common in nature and can arise from many evolutionary and 
ecological processes. Unfortunately, these species are not sufficiently 
studied to allow us to give a precise explanation for the disjunct 
distribution, or to determine with certainty whether it is disjunct. 
Information in the Background section discusses the fact that specimens 
of the subterranean species have not been found in well samples 
throughout the aquifer area, in spite of extensive sampling. The 
Service believes this is a good indication that the species are not 
widely distributed underground. We do believe that efforts to collect 
the species in any appropriate habitat where researchers were granted 
access were sufficient to determine that, in all probability, the 
species do not exist throughout the underground portions of the 
aquifer.
    Comment 8: Listing is not warranted until highly variable and 
interruptible spring flow is considered as part of the historical cycle 
to which these species are adapted to survive.
    Service Response: These species exhibit no morphological 
characteristics or behaviors indicating an ability to survive extended 
drying of their habitat. The Comal Springs riffle beetle lacks the 
ability to fly that many other riffle beetles have, suggesting that it 
is adapted to continuous and reliable spring flows (although flow may 
still be variable). The more frequent and severe drying that is 
expected at current and increasing rates of withdrawal from the aquifer 
will create a condition to which these species are not adapted to 
survive.
    Comment 9: As late as 1991, the Service made a warranted but 
precluded finding for Peck's cave amphipod. The proposed listing gives 
no explanation of the change in position from ``warranted but 
precluded'' to ``proposed for listing.'' This is ironic since potential 
threats to the species have been substantially addressed during this 4-
year period.
    Service Response: A warranted but precluded finding means that the 
best available information indicates that listing the species is 
appropriate but that other pending listing actions are more urgently 
needed and given a higher priority. Many of those other listing actions 
have now been completed. Before publishing the proposed listing, the 
Service reviewed the most current information available and determined 
that the threats to the species are still significant. The Service 
acknowledges and commends the efforts that so many individuals, 
agencies, and organizations have put into looking for ways to manage 
the Edwards Aquifer in a manner that will both protect the endemic 
species and provide for human water users. However, significant aquifer 
issues remain unresolved.
    Comment 10: Spring flow may be irrelevant to the suitability of 
habitat in the aquifer for the subterranean species.
    Service Response: The Service recognizes that the Peck's cave 
amphipod and the Comal Springs dryopid beetle are fully aquatic and 
show morphological adaptations to a subterranean existence. However, 
neither of these species has shown up in well samples and both have 
only been collected near the spring orifices, a key feature of their 
habitat is the water/spring orifice boundary. Reduced spring flows will 
alter the position and the nature of this boundary and may have a 
negative effect on these species. Further information is discussed in 
the Background section.
    Comment 11: The Service's failure to define a range or location of 
habitat for these species is tantamount to an

[[Page 66299]]

admission that the Service does not know enough about the species to 
warrant a conclusion that the species' habitat is threatened by 
drought.
    Service Response: The best available information indicates that the 
range of each species is limited to a small area near each spring 
opening where the species have been found. The range of each of the 
species is both small in size and probably disjunct in distribution. 
Further information on each species' habitat is presented in the 
Background section.
    Comment 12: Until more is known about the proposed species, and 
some real harm is shown as a consequence of variable and interruptible 
spring flows, they are not endangered species.
    Service Response: The Service must make determinations for listing 
of species based on ``the best scientific and commercial data 
available'' at the time of listing. Existing knowledge indicates that 
these species require a reliable supply of clean water. The species 
have survived past dry periods, but models and predictions cited in the 
proposal and in this final rule all agree that cessation of spring flow 
is likely to be more frequent and of longer duration given present 
pumping levels, as well as those outlined in S.B. 1477. Although S.B. 
1477 limits total water withdrawal from the aquifer, the limits may 
currently be too high to assure long-term spring flow. The Texas Water 
Development Board (1992) models indicate that at the proposed pumping 
limit of 450,000 acre-feet, and given recharge levels and patterns 
similar to those that occurred from 1934 to 1990, Comal Springs could 
spend 10 to 20 years below 100 cubic feet per second (cfs), and could 
stop flowing entirely for several years at a time (Texas Water 
Development Board, personal communication). Negative impacts to the 
habitat in spring run 1 at Comal Springs, including drying, occur as 
flows approach 100 cfs.
    Comment 13: Studies show that dissolved oxygen is high even at the 
lowest spring flows. Dissolved oxygen does not appear to be a 
determinative factor in the decision whether to list the species.
    Service Response: The primary factor threatening the long-term 
survival of these species is availability of a sufficient quantity of 
water to maintain essential characteristics of their habitat. Although 
water quality, including the need for certain levels of dissolved 
oxygen, may be an important factor in their survival, the magnitude of 
the threat from total loss of water is viewed as the greater threat.
    Comment 14: There is no economic advantage to protecting these 
invertebrates, and putting the life of virtually unknown species ahead 
of human welfare does not make sense.
    Service Response: Like these invertebrates, humans depend on 
reliable supplies of clean water, and thus protecting our water 
resources is vital to protecting human health. While the Service cannot 
consider the economic consequences of species listings when making 
listing determinations, we believe that protecting these species will 
have a positive effect to humans in that it will ensure the persistence 
of the water resource for future generations and will maintain a 
healthy ecosystem. In addition, continuing spring flow is economically 
important both in the vicinity of the springs for water recreation 
businesses and downstream as far as the Gulf of Mexico, where inflow of 
fresh water into the bays and estuaries is vital to recreational and 
commercial fisheries.

Summary of Factors Affecting the Species

    After a thorough review and consideration of all information 
available, the Service has determined that Peck's cave amphipod 
(Stygobromus pecki), Comal Springs riffle beetle (Heterelmis 
comalensis), and Comal Springs dryopid beetle (Stygoparnus comalensis) 
should be classified as endangered species. Procedures found at section 
4(a)(1) of the Act and regulations implementing the listing provisions 
of the Act (50 CFR part 424) were followed. A species may be determined 
to be endangered or threatened due to one or more of the five factors 
described in section 4(a)(1). These factors and their application to 
these three invertebrate species are as follows:

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

    The main threat to the habitat of these aquatic invertebrates is a 
reduction or loss of water of adequate quantity and quality, due 
primarily to human withdrawal of water from the San Antonio segment of 
the Edwards (Balcones Fault Zone) Aquifer and other activities. Total 
withdrawal from the San Antonio region of the Edwards Aquifer has been 
increasing since at least 1934, when the total well discharge was 
101,900 acre-feet (Edwards Underground Water District 1989). In 1989, 
the total well discharge was the highest on record at slightly more 
than 542,000 acre-feet (Longley 1991, Edwards Underground Water 
District 1992a). Between 1989 and 1995, total well discharge has ranged 
from 327,000 acre-feet in 1992 to 489,000 acre-feet in 1990 (U.S. 
Geological Survey, San Antonio, 1996).
    There is an integral connection between the water in the aquifer 
west of the springs and the water serving as habitat for these species. 
Water in the Edwards Aquifer flows from west to east or northeast and 
withdrawal or contamination of water in the western part of the aquifer 
can have a direct effect on the quantity and quality of water flowing 
toward the springs and at the spring openings. Prior to wells being 
drilled into the aquifer, almost all of the water entering the aquifer 
eventually exited at springs (Guadalupe-Blanco River Authority 1988).
    The Texas Water Commission (TWC) (1989) classified the San Antonio 
segment of the Edwards Aquifer as a critical area in terms of its 
potential for groundwater problems related to overdrafting. They also 
ranked Bexar, Comal, and Hays counties among the top 23 counties in 
Texas for number of active groundwater public supply systems. Human 
population in the region is expected to increase (Technical Advisory 
Panel 1990, Edwards Underground Water District 1993), which will result 
in increased demand for water from the aquifer.
    The Texas Water Development Board has applied its model (1992) of 
the Edwards Aquifer to determine the maximum pumping level that would 
allow Comal Springs to continue to flow, assuming historic recharge 
(Technical Advisory Panel 1990). They found that during a drought 
similar to that of the 1950's, the maximum pumpage that would allow 
spring flow at Comal Springs is about 250,000 acre-feet per year. ``At 
this pumping level, Comal Springs could be expected to maintain some 
annual flow although they may flow on an intermittent basis during a 
recurrence of the drought of record'' (Technical Advisory Panel 1990). 
The Panel also stated that in the year 2000, if pumping continues to 
grow at historical rates and a drought occurs, Comal Springs would go 
dry for a number of years (Technical Advisory Panel 1990).
    Wanakule (1990) states that ``the present problem facing the 
Edwards Aquifer is the threat of overdrafting of the annual average 
recharge rate.'' McKinney and Watkins (1993) evaluated the Texas Water 
Development Board model and other models and concluded that, without 
limiting withdrawal to about 200,000 acre-feet per year, Comal Springs 
will likely go

[[Page 66300]]

dry for extended periods during even a minor drought. The recent 
creation of the Authority may help to alleviate this threat to some 
degree (see Factor D for further discussion).
    The Texas Water Development Board model runs indicate that at the 
proposed pumping limit of 450,000 acre-feet, and given recharge levels 
and patterns similar to what occurred from 1934 to 1990, Comal Springs 
could spend 10 to 20 years below 100 cfs, and could stop flowing 
entirely for several years at a time (Texas Water Development Board, 
personal communication, 1997). A model run with the same general 
parameters but a withdrawal of 400,000 acre-feet shows the same pattern 
with some increase in spring flow, but still extended periods with no 
spring flow (Texas Water Development Board, personal communication, 
1997).
    In 1984 and 1990, some of the higher-elevation Comal Springs ceased 
flowing and water levels in the index well (J-17) in San Antonio 
dropped to within 3.7 meters (m) (12 feet (ft)) of the historic low of 
186.7 m (612.5 ft) that occurred in 1956 (Wanakule 1990). During the 
drought conditions in the summer of 1996, spring flows at Comal Springs 
dropped to a low of 83 cfs. During the entire year of 1996, spring flow 
stayed below 200 cfs for about 252 days and below 100 cfs, the 
approximate flow at which spring run 1 stops flowing, for about 59 
days. Because these invertebrates require relatively well-oxygenated 
water, a reduction or cessation of spring flows, even if standing water 
remains around the spring orifices, may negatively impact the species. 
Complete loss of water would likely result in the extirpation of these 
aquatic species.
    In addition to a loss of water, a decrease in the water level in 
the aquifer could lead to decreased water quality at the springs. The 
Balcones Fault Zone--San Antonio Region is bounded on the south and 
east by a ``bad water'' interface across which the groundwater quality 
abruptly deteriorates to greater than 1000 mg/l total dissolved solids. 
Crossing the bad water interface, groundwater goes from fresh to saline 
or brackish. Lowered water levels resulting from groundwater pumpage 
and/or decreased recharge may at some point result in deterioration of 
water quality in the fresh water section of the aquifer through 
movement of the bad water interface. The Comal and San Marcos Springs 
are less than 305 and 62 m (1,000 and 200 ft), respectively, from the 
bad water interface (TWC 1989, Edwards Underground Water District 
1992b). Although the data are inconclusive at present, even a small 
movement of the water may negatively impact the species.
    Other possible effects of reduced spring flow exist. These include 
changes in the chemical composition of the water in the aquifer and at 
the springs, a decrease in current velocity and corresponding increase 
in siltation, and an increase in temperature and temperature 
fluctuations in the aquatic habitat (McKinney and Watkins 1993).
    Another threat to the habitat of these species is the potential for 
groundwater contamination. Pollutants of concern include, but are not 
limited to, those associated with human sewage (particularly septic 
tanks), leaking underground storage tanks, animal/feedlot waste, 
agricultural chemicals (especially insecticides, herbicides, and 
fertilizers) and urban runoff (including pesticides, fertilizers, and 
detergents).
    Pipeline, highway, and railway transportation of hydrocarbons and 
other potentially harmful materials in the Edwards Aquifer recharge 
zone and its watershed, with the attendant possibility of accidents, 
present a particular risk to water quality in Comal and San Marcos 
Springs. Comal and San Marcos Springs are both located in urbanized 
areas. Hueco Springs is located alongside River Road, which is heavily 
traveled for recreation on the Guadalupe River, and may be susceptible 
to road runoff and spills related to traffic. Fern Bank Springs is in a 
relatively remote, rural location and its principal vulnerability is 
probably to contaminants associated with leaking septic tanks, animal/
feedlot wastes, and agricultural chemicals.
    Of the counties containing portions of the San Antonio segment of 
the Edwards Aquifer, the potential for acute, catastrophic 
contamination of the aquifer is greatest in Bexar, Hays, and Comal 
counties because of the greater level of urbanization compared to the 
western counties. Although spill or contamination events that could 
affect water quality do happen to the west of Bexar County, dilution 
and the time required for the water to reach the springs may lessen the 
threat from that area. As aquifer levels decrease, however, dilution of 
contaminants moving through the aquifer may also decrease.
    The TWC reported that in 1988 within the San Antonio segment of the 
Edwards Aquifer, Bexar, Hays, and Comal counties had the greatest 
number of land-based oil and chemical spills in central Texas that 
affected surface and/or groundwater with 28, 6, and 4 spills, 
respectively (TWC 1989). As of July, 1988, Bexar County had between 26 
and 50 confirmed leaking underground storage tanks, Hays County had 
between 6 and 10, and Comal County had between 2 and 5 (TWC 1989) 
putting them among the top 5 counties in central Texas for confirmed 
underground storage tank leaks. The TWC estimates that, on average, 
every leaking underground storage tank will leak about 500 gallons per 
year of contaminants before the leak is detected. These tanks are 
considered one of the most significant sources of groundwater 
contamination in the state (TWC 1989).
    The TWC (1989), using the assessment tool DRASTIC (Aller, et al. 
1987), classified aquifers statewide according to their pollution 
potential. The Edwards Aquifer (Balcones Fault Zone--Austin and San 
Antonio Regions) was ranked among the highest in pollution potential of 
all major Texas aquifers. The project's objective was to identify areas 
sensitive to groundwater pollution from a contaminated land surface 
based on the hydrogeologic setting. The area of particular concern was 
the Edwards Aquifer recharge zone and its watershed.
    The TWC (1989) also reviewed and reported known and potential risks 
to Texas aquifers, such as from sanitary landfills, hazardous waste 
disposal facilities, industrial waste and sewage disposal wells, 
commercial feedlots, and graveyards. They found the following: ``Based 
on this statewide assessment of potential and actual ground-water 
contaminants, waste disposal practices being employed and existing 
regulations which are available for contamination detection and 
mitigation, it was concluded that there are still conditions that exist 
or practices being used that are cause for concern. For the most part, 
the state presently has in place regulations that will effectively 
reduce future pollution, however past practices may return to haunt 
us.''

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

    No threat from overutilization of this species is known at this 
time.

C. Disease or Predation

    While individuals of these three species may be preyed upon by 
various predatory insects or fish, no information indicates that this 
is a substantial threat.

D. The Inadequacy of Existing Regulatory Mechanisms

    Invertebrates are not included on the Texas Parks and Wildlife 
Department's (TPWD) list of threatened and endangered species and are 
provided no protection by the State. The TPWD

[[Page 66301]]

regulations do not contain provisions for protecting habitat of any 
listed species.
    Traditionally, the State of Texas has had no authority to regulate 
withdrawal of groundwater from an aquifer. After a lawsuit filed 
against the Service by the Sierra Club (Sierra Club v. Babbitt, 
formerly Sierra Club v. Lujan), the Texas State Legislature passed a 
bill (S.B. 1477) authorizing the creation of the Authority and granted 
the Authority the power to regulate groundwater withdrawal from the 
Edwards Aquifer. The bill limits groundwater withdrawal from the 
aquifer to 450,000 acre-feet per year initially, reducing it to 400,000 
acre-feet per year by January 1, 2008. However, Texas Water Development 
Board models indicate that, at these proposed withdrawal limits, the 
upper-elevation spring runs at Comal Springs could go dry frequently 
and for significant periods of time (as happened in 1996) and 
significant negative impacts to the species could occur before 
continuous minimum springflows are in place.
    One goal of the bill is to provide continuous minimum spring flow, 
as defined by Federal statute, at Comal and San Marcos Springs by the 
year 2012. This minimum flow is to protect species that are designated 
as threatened or endangered under Federal or State law, but does not 
protect unlisted species. In addition, an evaluation of the Texas Water 
Development Board models used to set these withdrawal limits shows that 
flow at Comal Springs will drop below 100 cfs and will likely go dry 
for extended periods in time of severe drought and probably during 
minor droughts (McKinney and Watkins 1993, TWDB 1992). McKinney and 
Watkins (1993) believe it is unlikely that spring flow in Comal Springs 
of at least 100 cfs for 80 percent of the time, except during severe 
drought, can be met with a pumping limit greater than 200,000 acre-feet 
per year. In addition, when the flow drops to 96 cfs, spring run 1 at 
Comal Springs has already dried substantially (Thornhill, deposition in 
Sierra Club v. Lujan). Finally, efforts to maintain minimum spring flow 
at Comal and San Marcos Springs would not necessarily be sufficient to 
maintain flow at Hueco and Fern Bank Springs, which lie at higher 
elevations.

E. Other Natural or Manmade Factors Affecting Their Continued Existence

    The effect of natural droughts in south central Texas will increase 
in severity due to the large increase in human groundwater withdrawals 
(Wanakule 1990). These species' very limited habitat is likely to be 
lost through drying or decreased volume of spring flow during minor or 
severe drought.
    At present, competition is not known to be a significant threat to 
these species. However, two exotic snail species, Thiara granifera and 
Thiara tuberculata, are common in the spring runs and, as grazers, may 
compete for food. Another exotic species, the giant ramshorn snail 
(Marisa cornuarietis), is present in two of the spring runs and may 
colonize the other runs at low flow levels. Marisa can have a 
tremendous impact on vegetation, that in turn may affect the habitat 
for surface-dwelling grazers like the riffle beetle.
    The Service has carefully assessed the best scientific and 
commercial information available regarding the past, present, and 
future threats faced by these species in making this final rule. Based 
on this evaluation the preferred action is to list the Peck's cave 
amphipod (Stygobromus pecki), Comal Springs riffle beetle (Heterelmis 
comalensis), and Comal Springs dryopid beetle (Stygoparnus comalensis) 
as endangered. Endangered status is determined appropriate for these 
three invertebrates given that threats are significant and could result 
in extinction of these species throughout all or a significant portion 
of their range. The immediate nature of these threats precluded 
determining these species to be threatened species.

Critical Habitat

    Critical habitat is defined in section 3 of the Act as: (i) The 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) specific areas outside the 
geographical area occupied by a species at the time it is listed, upon 
a determination that such areas are essential for the conservation of 
the species. ``Conservation'' means the use of all methods and 
procedures needed to bring the species to the point at which listing 
under the Act is no longer necessary.
    Section 4(a)(3) of the Act, as amended, and implementing 
regulations (50 CFR 424.12), require that, to the maximum extent 
prudent and determinable, the Secretary designate critical habitat at 
the time the species is determined to be endangered or threatened. The 
Service finds that designation of critical habitat is not prudent for 
Peck's cave amphipod, the Comal Springs riffle beetle, and the Comal 
Springs dryopid beetle. Service regulations (50 CFR 424.12(a)(1)) state 
that designation of critical habitat is not prudent when one or both of 
the following situations exist: (1) The species is threatened by taking 
or other human activity, and identification of critical habitat can be 
expected to increase the degree of threat to the species, or (2) such 
designation of critical habitat would not be beneficial to the species.
    Designation of critical habitat would provide no benefits to these 
species beyond those provided by listing and the subsequent evaluation 
of activities under section 7 of the Act. Section 7 prohibits Federal 
agencies from jeopardizing the continued existence of listed species or 
destroying or adversely modifying listed species' designated critical 
habitat.
    In the Service's section 7 regulations at 50 CFR part 402, the 
definition of ``jeopardize the continued existence of '' includes ``to 
reduce appreciably the likelihood of both the survival and recovery of 
the listed species,'' and ``destruction or adverse modification'' is 
defined as ``a direct or indirect alteration that appreciably 
diminishes the value of critical habitat for both the survival and 
recovery of a listed species.'' Both of these definitions refer to 
actions that reduce the survival and recovery of a listed species. Any 
action that would appreciably diminish the value, in quality or 
quantity, of spring flows (habitat) on which the species depend would 
also reduce appreciably the likelihood of survival and recovery of the 
three species. Because these species are endemic to such highly 
localized areas, actions that affect water quality and quantity at the 
springs will be fully evaluated for their effects on the three species 
through analysis of whether the actions would be likely to jeopardize 
their continued existence. The analysis for possible jeopardy applied 
to these species would therefore be identical to the analysis for 
determining adverse modification or destruction of critical habitat. 
Therefore, there is no distinction between jeopardy and adverse 
modification for activities impacting the springs on which these 
species depend.

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
practices. Recognition through listing encourages and results in public 
awareness and conservation actions by Federal, State, and local 
agencies, private

[[Page 66302]]

organizations, and individuals. The Act provides for cooperation with 
the States and requires that recovery actions be carried out for all 
species. The protection required of Federal agencies and the 
prohibitions against taking and harm are discussed, in part, below.
    Conservation and management of the Peck's cave amphipod, Comal 
Springs riffle beetle, and Comal Springs dryopid beetle are likely to 
involve protection and conservation of the Edwards Aquifer and spring 
flow at Comal, Hueco, San Marcos, and Fern Bank Springs. It is also 
anticipated that listing will encourage research on critical aspects of 
the species' biology.
    Section 7(a) of the Act, as amended, requires Federal agencies to 
evaluate their actions with respect to any species that is proposed or 
listed as endangered or threatened and with respect to its critical 
habitat, if any is being designated. Regulations implementing this 
interagency cooperation provision of the Act are codified at 50 CFR 
part 402. Section 7(a)(4) requires Federal agencies to confer 
informally with the Service on any action that is likely to jeopardize 
the continued existence of a proposed species. If a species is listed 
subsequently, section 7(a)(2) requires Federal agencies to ensure that 
activities they authorize, fund, or carry out are not likely to 
jeopardize the continued existence of such species or to destroy or 
adversely modify its critical habitat.
    If a Federal action may affect a listed species or its critical 
habitat, the responsible Federal agency must enter into formal 
consultation with the Service. Federal actions that may require 
consultation include projects that would affect the quality or quantity 
of water within the San Antonio segment of the Edwards Aquifer or 
otherwise significantly affect the outlets or water output of Comal 
Springs in New Braunfels, Texas; San Marcos Springs in San Marcos, 
Texas; Hueco Springs in Comal County, Texas; and Fern Bank Springs in 
Hays County, Texas. Examples of these types of activities include 
projects that would involve withdrawal of water from the aquifer; 
permits for municipal wastewater discharge; agricultural irrigation; 
use of pesticides and herbicides; Environmental Protection Agency 
National Discharge Elimination System permits; section 18 exemptions 
under the Federal Insecticide, Fungicide, and Rodenticide Act; Corps of 
Engineers permits for stream crossings; and Department of Housing and 
Urban Development projects.
    The Act and implementing regulations found at 50 CFR 17.21 set 
forth a series of general prohibitions and exceptions that apply to all 
endangered wildlife. These prohibitions, in part, make it illegal for 
any person subject to the jurisdiction of the United States to take 
(includes harass, harm, pursue, hunt, shoot, wound, kill, trap, or 
collect, or to attempt any of these), import or export, ship in 
interstate commerce in the course of commercial activity, or sell or 
offer for sale in interstate or foreign commerce any listed species. It 
also is illegal to possess, sell, deliver, carry, transport, or ship 
any such wildlife that has been taken illegally. Certain exceptions 
apply to agents of the Service and State conservation agencies.
    Permits may be issued to carry out otherwise prohibited activities 
involving endangered wildlife species under certain circumstances. 
Regulations governing permits are at 50 CFR 17.22 and 17.23. Such 
permits are available for scientific purposes, to enhance the 
propagation or survival of the species, and/or for incidental take in 
connection with otherwise lawful activities. It is anticipated that few 
trade permits would ever be sought or issued because these species are 
not known to be in trade.
    It is the policy of the Service (July 1, 1994; 59 FR 34272) to 
identify to the maximum extent practicable at the time a species is 
listed those activities that would or would not constitute a violation 
of section 9 of the Act. The intent of this policy is to increase 
public awareness of the effect of listing on proposed and ongoing 
activities within a species' range. The purpose of this guidance is not 
only to identify activities that would or would not likely result in 
take of individuals, but activities that in combination will ultimately 
affect the long-term survival of these species. This guidance should 
not be used to substitute for local efforts to develop and implement 
comprehensive management programs.
    The Service believes that, based on the best available information, 
activities that could potentially harm these invertebrates and result 
in ``take'' include, but are not limited to:
    (1) Collecting or handling of the species;
    (2) Activities that may result in destruction or alteration of the 
species' habitat including, but not limited to, withdrawal of water 
from the aquifer to the point at which habitat becomes unsuitable for 
the species, alteration of the physical habitat within the spring runs, 
or physical alteration of the spring orifices or of the subsurface 
pathways providing water to the springs;
    (3) Discharge or dumping of chemicals, silt, pollutants, household 
or industrial waste, or other material into the springs or into areas 
that provide access to the aquifer and where such discharge or dumping 
could affect water quality;
    (4) Herbicide, pesticide, or fertilizer application in or near the 
springs containing the species; and
    (5) Introduction of non-native species (fish, plants, other) into 
these spring ecosystems.
    The Service believes that a wide variety of activities would not 
harm these species if undertaken in the vicinity of their habitats and 
thus would not constitute taking. In general, any activity in the 
contributing, recharge, or artesian zones of the Edwards aquifer that 
would not have potential for the cumulative or acute/catastrophic 
negative effects on water quantity or quality within the aquifer should 
not harm these species. Inquiries concerning the possible effects of 
specific activities, copies of regulations regarding listed wildlife, 
or inquiries regarding prohibitions and permits should be directed to 
the Service's Austin Field Office (see ADDRESSES section).

National Environmental Policy Act

    The Fish and Wildlife Service has determined that Environmental 
Assessments and Environmental Impact Statements, as defined under the 
authority of the National Environmental Policy Act of 1969, need not be 
prepared in connection with regulations adopted pursuant to section 
4(a) of the Endangered Species Act of 1973, as amended. A notice 
outlining the Service's reasons for this determination was published in 
the Federal Register on October 25, 1983 (48 FR 49244).

Required Determinations

    The Service has examined this regulation under the Paperwork 
Reduction Act of 1995 and found it to contain no information collection 
requirements.

References Cited

Aller, L., T. Bennett, J.H. Lehr, R.J. Petty, and G. Hackett. 1987. 
DRASTIC: a standardized system for evaluating groundwater pollution 
potential using hydrogeologic settings. U.S. Environmental 
Protection Agency. EPA/600/2-87/035. 622 pp.
Arsuffi, Thomas L. 1993. Status of the Comal Springs Riffle Beetle 
(Heterelmis comalensis Bosse, Tuff, and Brown), Peck's Cave Amphipod 
(Stygobromus pecki Holsinger), and the Comal Springs Dryopid Beetle 
(Stygoparnus comalensis Barr and Spangler). Prepared for the U.S. 
Fish and Wildlife Service. 25 pp.

[[Page 66303]]

Barr, C.B. 1993. Survey for two Edwards Aquifer invertebrates: Comal 
Springs dryopid beetle Stygoparnus comalensis Barr and Spangler 
(Coleoptera: Dryopidae) and Peck's cave amphipod Stygobromus pecki 
Holsinger (Amphipoda: Crangonyctidae). Prepared for U.S. Fish and 
Wildlife Service. 70 pp.
Barr, C.B., and P.J. Spangler. 1992. A new genus and species of 
stygobiontic dryopid beetle, Stygoparnus comalensis (Coleoptera: 
Dryopidae), from Comal Springs, Texas. Proc. Biol. Soc. Wash. 
105(1):40-54.
Bosse, L.S., D.W. Tuff, and H.P. Brown. 1988. A new species of 
Heterelmis from Texas (Coleoptera: Elmidae). Southwestern Naturalist 
33(2):199-203.
Brown, H.P. 1987. Biology of Riffle Beetles. Annual Review of 
Entomology. 32:253-73
Brown, H.P., and C.B. Barr. 1988. First report of stygobiontic 
(subterranean) riffle beetles in North America. Program abstract for 
April 22, 1988, meeting of Southwestern Association of Naturalists. 
5 pp.
Brune, G. 1981. Springs of Texas, Volume 1. Branch-Smith Inc., Ft. 
Worth, Texas.
Chapman, R.F., 1982. The Insects: Structure and Function. Harvard 
University Press, Cambridge, MA. 919 pp.
Edwards Underground Water District. 1989. Compilation of hydrologic 
data for the Edwards Aquifer, San Antonio area, Texas, 1988, with 
1934-88 summary: Bulletin 48, 157 pp.
Edwards Underground Water District. 1992a. Report of the technical 
data review panel on the water resources of the south central Texas 
region. 307 pp.
Edwards Underground Water District. 1992b. Investigation of the 
fresh/saline water interface in the Edwards Aquifer in New Braunfels 
and San Marcos, Texas. Report 92-02. 18 pp.
Edwards Underground Water District. 1993. Urban Development on the 
Edwards Aquifer Recharge Zone. Report 93-09. 40 pp.
Guadalupe-Blanco River Authority. 1988. The Edwards Aquifer: 
Underground River of Texas. Guadalupe-Blanco River Authority, 
Seguin, Texas. 63 pp.
Holsinger, J.R. 1967. Systematics, speciation, and distribution of 
the subterranean amphipod genus Stygonectes (Gammaridae). Bull. U.S. 
Nat. Mus. 259:1-176.
Longley, G. 1991. Status and trends of the Edwards (Balcones Fault 
Zone) Aquifer in the San Antonio Region. pp. 4-18 In: Proceedings of 
South Texas Irrigation Conference. Guy Fipps, ed. 146 pp.
McKinney, D.C., and D.W. Watkins, Jr. 1993. Management of the 
Edwards Aquifer: A critical assessment. Technical Report CRWR 244. 
Center for Research in Water Resources, Bureau of Engineering 
Research. University of Texas at Austin. 94 pp.
Technical Advisory Panel. 1990. Technical factors in Edwards Aquifer 
use and management. Prepared for Special Committee on the Edwards 
Aquifer. 57 pp.
Texas Department of Water Resources. 1979. Geohydrology of Comal, 
San Marcos, and Hueco Springs. Report 234. Prepared by Guyton ans 
Associates. 85 pp.
Texas Water Commission. 1989. Ground-water quality of Texas-an 
overview of natural and man-affected conditions. Austin, Texas. 197 
pp. and 3 plates.
Texas Water Development Board. 1992. Model Refinement and 
Applications for the Edwards (Balcones Fault Zone) Aquifer for the 
San Antonio Region, Texas. Texas Water Development Board. Report 
340. July 1992. 33 pp.
U.S. Geological Survey. 1996. Unpublished summary tables on Edwards 
Aquifer discharge. U.S. Geological Survey, San Antonio. 3 pp.
Wanakule, N. 1990. Stochastic drought analysis of the Edwards 
Aquifer. Edwards Aquifer Research and Data Center No. R1.-90, San 
Marcos, Texas. 32 pp.

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, and Transportation.

Regulation Promulgation

    Accordingly, part 17, subchapter B of chapter I, title 50 of the 
Code of Federal Regulations, the Service amends as follows:

PART 17--[AMENDED]

    1. The authority citation for Part 17 continues to read as follows:

    Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C. 
4201-4245; Pub. L. 99-625, 100 Stat. 3500, unless otherwise noted.

    2. Section 17.11(h) is amended by adding the following, in 
alphabetical order under Crustaceans and Insects, respectively, to the 
List of Endangered and Threatened Wildlife to read as follows:


Sec. 17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------
                        Species                                                                                                                         
--------------------------------------------------------    Historic range           Family            Status      When listed    Critical     Special  
         Scientific name                Common name                                                                               habitat       rules   
--------------------------------------------------------------------------------------------------------------------------------------------------------
           Crustaceans                                                                                                                                  
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
Stygobromus (=Stygonectes) pecki.  Amphipod, Peck's      U.S.A. (TX)........  Crangonyctidae.....  E               ...........           NA           NA
                                    cave.                                                                                                               
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
             Insects                                                                                                                                    
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
Stygoparnus comalensis...........  Beetle, Comal         U.S.A. (TX)........  Dryopidae..........  E               ...........           NA           NA
                                    Springs dryopid.                                                                                                    
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
Heterelmis comalensis............  Beetle, Comal         U.S.A. (TX)........  Elmidae............  E               ...........           NA           NA
                                    Springs riffle.                                                                                                     
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 66304]]

    Dated: October 21, 1997.
Jamie Rappaport Clark,
Director, Fish and Wildlife Service.
[FR Doc. 97-33041 Filed 12-17-97; 8:45 am]
BILLING CODE 4310-55-P