(DRAFT) - Taxonomy
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
TAXONOMY
NAME - GAMBUSIA, CLEAR CREEK
OTHER COMMON NAMES - GAMBUSIA and CLEAR CREEK
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - OSTEICHTHYES,
ORDER AND SUBORDER - ATHERINIFORMES,
FAMILY AND SUBFAMILY - POECILIIDAE,
GENUS AND SUBGENUS - GAMBUSIA,
SPECIES AND SSP - HETEROCHIR,
SCIENTIFIC NAME - GAMBUSIA HETEROCHIR
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Clear Creek Gambusia
Gambusia heterochir Hubbs, 1953
KINGDOM: Animal GROUP: Fish
PHYLUM: Chordata CLASS: Osteichthyes
ORDER: Atheriniformes FAMILY: Poeciliidae
The Clear Creek gambusia (Gambusia heterochir Hubbs, 1953) is a
stocky Poeciliid with a metalic blue sheen. A series of crescentic
dark marks on the posterior margin of lateral scales from a
crosshatched pattern. There is no predorsal dark streak or caudal
speckling. Females have a pronounced darkening around the anus. A
deep notch on the dorsal margin of the pectoral fin of adult males is
unique among Poeciliids. The gonopodium is blunt with short spines on
ray 3, a pronounced elbow and separate distal elements on ray 4A, a
simple terminal hook on 4P, and a rounded terminal hook on ray 5.
The Clear Creek gambusia (Gambusia heterochir) once was
considered to be a member of the Gambusia nicarguensis species group
(01) but is now generally considered to be a member of the G. nobilis
species group (02,03,04,05,06,07).
The holotype and several paratypes are deposited in the
University of Michigan Museum of Zoology. Most specimens are
Taxonomy - 1 (DRAFT) - Taxonomy
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
deposited at the Texas Natural History Collection.
Illustrations may be found in (01) and in (08).
Taxonomy - 2 (DRAFT) - Status
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Clear Creek gambusia (Gambusia heterochir) has been
designated an Endangered species pursuant to the Endangered Species
Act of 1973 (50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C.
1531-1540), as amended. The species has this status wherever found
including the State of Texas.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild
animal (alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Texas
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: Texas Parks and Wildlife Department
STATE STATUTE: 31 Texas Administrative Code Sec. 57.133 (127.30.
003) July 1977
Status - 1 (DRAFT) - Status
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The Clear Creek gambusia is listed in the IUCN Red Data Book,
Vol. 4, 1977; and is also listed by the Convention on Nature
Protection and Wildlife Preservation in the Western Hemisphere,
1970.
ECONOMIC STATUSES:
This species has value to naturalists and has a value as a
component of Texas' natural heritage of biotic diversity.
67/03/11:32 FR 04001/ - Listing as Endangered
79/05/21:44 FR 29565/29577 - Five year review
85/07/22:50 FR 29901/29909 - Five year review
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
INLAND AQUATIC
LAND USE -
Shrub and Brush Rangeland
Streams and Canals
Reservoirs
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Lacustrine, littoral AB4
COMMENTS ON HABITAT ASSOCIATIONS -
The Clear Creek gambusia (Gambusia heterochir) occurs in the
headwaters of Clear Creek, Menard County, Texas, 16.7 km west of
Menard. Upper Clear Creek consists of a series of limestone springs
(Wilkinson Springs) (07) at the base of a limestone cliff (06); with
the springs originating from the Edwards Aquifer (07). The watershed
emptying into Clear Creek is extremely limited encompassing about 10
hectares (07), forming intermittent creeks each about 1 km long
(with 1 square kilometer basins) and emptying into Clear Creek
downstream of the head pool (07).
Originally Clear Creek was a clear spring run that flowed about 5
km to its confluence with the San Saba River. Most or all the stream
was probably inhabited by G. heterochir, Hyalella texana (amphipod),
Ceratophyllum sp. and associated organisms (07).
Presently Clear Creek has an elevational diference of about 15 m
from headspring to confluence. Dam 1, built before 1890, forms the
present head pool. Dam 2 is constructed 1.5 km downstream from Dam 1
and backs water to the base of Dam 1. Dam 3 (approximately the same
elevation as Dam 2) was constructed 1.5 km downstream of Dam 2 and
Dam 4 was built 0.4 km downstream of Dam 3 and 100 m upstream of U.S.
Highway 190. The resulting changes in habitat encourage population
build-ups of eurythermal organisms overwhelming the springrun fauna
except for those isolated upstream of Dam 1 (07).
The Clear Creek gambusia occurs in stenothermal (ca 20 degrees C)
spring environments with dense growths of Cerotophyllum and Ludwegia.
A relatively low pH (ca 6.5) is positively associated with Clear Creek
gambusia abundance (06). Reduction in spring flow and/or riparian
development activities (e.g., resort housing) that drain, silt, and/or
introduce pesticides/herbicides into the spring pool are the primary
hazards (07). Some of these factors could also cause eutrophic
conditions.
The Clear Creek gambusia habitat is obviously dependent upon a
reliable and substantial supply of spring water; therefore, it is
essential that the Edwards-Trinity Aquifer recharge zone remain
undisturbed. Most of the local recharge zone appears to be in
ranchland north and west of the headspring.
Surrounding shrub/brush rangeland is classified as Texas savanna,
and usage is primarily ranchland.
Habitat Associations - 1 (DRAFT) - Food Habits
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
LIFESTAGE FOOD FOOD PART
General Zooplankton
General Arthropods
General Worms
General Fish
General Crustaceans
Food Habits - 1 (DRAFT) - Environment Associations
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Aquatic Features: Springs [flowing]
G Terrestrial Features: Cliffs/ledges
Environment Associations - 1 (DRAFT) - Life History
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
The primary food eaten by adults is the amphipod, Hyalella texana
(80 percent) (06,12). It is presumed that small Gambusia eat small
Hyalella. In culture the Clear Creek gambusia eats a wide variety of
foods (13) and would presumably do so in nature if available.
HOME RANGE/TERRITORY:
Males are semiterritorial during the breeding season - alpha
males occupy "preferred habitat"; omega males occupy "suboptimal
habitat " (vulnerable to predation and having fewer females). Females
abound in preferred habitat (06).
PERIODICITY:
Diurnal - activity peaks at 0800 and 1800 (06). The species is
active in all seasons (the water is stenothermal).
MIGRATION PATTERNS:
No migrations are known for the Clear Creek gambusia (Gambusia
heterochir).
COVER/SHELTER REQUIREMENTS:
G. heterochir is most abundant in shallow waters with dense
growths of Ceratophyllum and Ludwegia (01,06,09).
REPRODUCTIVE SITE REQUIREMENTS:
Nothing is known for the Clear Creek gambusia regarding
reproductive site requirements.
REPRODUCTIVE CHARACTERISTICS:
This species is viviparous (a live bearer) with 2 generations per
year and seldom lives more than one year in nature, but may live more
than 2 years in the laboratory. Females reproduce in February-
October; have 6 broods per year; are promiscuous with internal
fertilization (sperm may be stored several months); and multiple
inseminations (per brood) may occur. Gestation is 40 days. Clutch
size is dependent upon size of female, and up to 100 young may be
produced per brood. Relative brood numbers are seasonally dependant
with a maximum in August, but high in May-September (06).
PARENTAL CARE:
No parental care is known.
POPULATION BIOLOGY:
Occurs in stenothermal waters in Clear Creek, unable to coexist
with Gambusia affinis in eurythermal waters. Present population
densities are over 1/square meter in optimal environments.
SPECIES INTERRELATIONSHIPS:
The Clear Creek gambusia (Gambusia heterochir) primarily feeds on
Hyalella texana (an amphipod) (06,12). This species does not coexist
with G. affinis in eurythermal environments (06). G. heterochir
Life History - 1 (DRAFT) - Life History
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
hybridizes with G. affinis (06,11). An apparently recent introduction
to Clear Creek is the rainwater killifish (Lucania parva), first
collected in 1980. The rainwater killifish is a brackishwater species
formerly known only from coastal waters and the Pecos River, but is
expected to reproduce in Clear Creek. If the killifish reproduces and
becomes established in Clear Creek, its impact on G. heterochir cannot
be predicted. Both Lucania and G. heterochir occupy similar niches
and are likely to compete for food and cover (07).
A variety of potential predators which presumably feed on
gambusia have been recorded in Clear Creek. These include the
largemouth bass (Micropterus salmoides), green sunfish (Lepomis
cyanellus), longear sunfish (Lepomis megalotis), exotic redear sunfish
(Lepomis microlophus), and yellow bullhead (Ictalurus natalis).
Semi-aquatic snakes (Nerodia sp. and Thamnophis sp.) and bullfrogs
(Rana catesbeiana) have been seen along shore and likely feed on
gambusia. These piscivorous vertebrates have a long history of
occurrence in central Texas and their predation would be a normal
selective factor on G. heterochir. Unless the habitat is seriously
altered (e.g., removal of aquatic plants), the predatory activities
of these vertebrates are not expected to deplete the gambusia
seriously (07).
OTHER LIFE HISTORY DESCRIPTORS:
Clear Creek gambusia cohabit the upper pool with the roundnose
minnow (Dionda episcopa) and the greenthroat darter (Etheostoma
lepidum). These small fishes have minimal environmental overlap.
Dionda is a midwater fish with omnivorous food habits; Etheostoma and
gambusia feed on small invertebrates such as Hyalella, but Etheostoma
lives on the substrate and gambusia lives near the surface. Two
anurans (Acris crepitans and Rana berlandieri) occupy the shores of
the upper pool and may occasionally feed on aquatic invertebrates on
the surface. Their tadpoles inhabit the shores of the upper pool,
but are herbivores.
Life History - 2 (DRAFT) - Management Practices
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Maintaining/Controlling Water Flow
Beneficial Developing/maintaining/protecting wetlands
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Land Acquisition
Beneficial Water Right Acquisition
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Reforestation
Beneficial Stocking captive-reared wild-strain animals
Beneficial Controlling/Removing Exotic Vertebrates
Adverse Low Gene Pool
Existing Low Gene Pool
Adverse Hybridization
Existing Hybridization
Adverse Water Temperature Alteration
Existing Water Temperature Alteration
Adverse Water Level Stabilization
Existing Water Level Stabilization
Adverse Flooding
Existing Flooding
Adverse Groundwater drawdown
Existing Groundwater drawdown
Adverse Reservoirs
Existing Reservoirs
Adverse Migration barriers
Existing Migration barriers
Adverse Shoreline modification/development
Existing Shoreline modification/development
Adverse Applying herbicides
Existing Applying herbicides
Adverse Applying pesticides
Existing Applying pesticides
Adverse Competition
Existing Competition
Adverse Exotic/Feral/Introducted Species
Existing Exotic/Feral/Introducted Species
Adverse
Existing
COMMENTS ON MANAGEMENT PRACTICES -
Upper Clear Creek has been altered extensively for irrigation
and domestic uses. Prior to 1900, a low, earth-concrete dam was
built about 75 meters downstream from the headsprings. Three
additional dams were built downstream from the original dam in the
1930's, ponding water to the base of each subsequent dam (06) and
flooding previously irrigated fields (07).
The Clear Creek gambusia (Gambusia heterochir) is a spring
dwelling species, limited to stenothermal headsprings in Clear Creek,
Management Practices - 1 (DRAFT) - Management Practices
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
Menard County, TX. This ecosystem is unique in having a relatively
low pH (ca. 6.5), with the presence of Hyalella texana (an amphipod)
and a species of Ceratophyllum. Adjacent eurythermal ponded waters
are dominated by a relatively high pH (7.4-7.8), Hyalella azteca and a
species of Myriophyllum (09). The eurythermal environment is
inhabited by Gambusia affinis and no self-sustaining Gambusia
heterochir populations exist there. Virtually the entire length of
Clear Creek is impounded (07) and only areas around springs have
sufficient inflow to maintain the stenothermal environment. The
vast majority of the stenothermal surface area is in the upper pool
(100 x 70 m - triangular) (06,09) and a secondary spring area
(20 x 40 m) is located 250 meters east and had virtually no Gambusia
heterochir prior to 1970. Subsequent to the release of the exotic
fish; Lucinia parva, presumbaly from Texas coastal waters (10),
Gambusia heterochir became more abundant than G. affinis (11). A
minor and presumably not self-sustaining population occurs in a spring
area on west bank, 50 meters south of the head spring pool. At one
time a population also existed on the west bank at another spring
25 meters south of the spring pool (09).
The presumed major cause for the restricted distribution of the
Clear Creek gambusia was the construction of an earth dam, 3 km
east of the head springs (07). That dam backs water (eurythermal) to
the base of the dam forming the headspring pool. This established an
environment more suitable for G. affinis and a substantial reduction
in the range from 3 kilometers of stream to the present two ponded
regions.
The environmental limitations are exacerbated by hybridization
with G. affinis. This hazard was substantial in the upper spring pool
due to breaches in the dam, prior to 1979 (06). In 1979 the spring
pool dam was reconstructed to preclude immigration by G. affinis.
Hybrid abundance was reduced from 10 percent of the Gambusia prior to
1970 to 5 percent in 1980 and 1 percent in 1984. Between 1980 and
1984 G. affinis abundance declined from 30 to 20 percent; the Clear
Creek gambusia abundance went from 60 percent in 1970 to 65 percent in
1980 to 75 percent in 1984, presumably as a result of the blocking of
immigration by G. affinis (11).
Although the present abundance is much greater than in 1970 (and
especially in 1978 when the upper dam was about to collapse entirely)
the geographic range of the Clear Creek gambusia is very restricted.
Although G. heterochir can be maintained in a variety of environments
in the laboratory, the restriction to stenothermal waters in nature
suggests a biological factor, perhaps competition, as the major factor
limiting distribution (07).
Any alteration (i.e., groundwater drawdown) to the aquifer or the
immediate surroundings of the headspring pool (the ranch was sold in
1984) could have disasterous results. Reduction in spring flow and/or
riparian development activities (e.g., resort housing) that drain,
silt, and/or introduce pesticides/herbicides into the spring pool are
the primary hazards (07). Some of these factors could also cause
eutrophic conditions. Any development in the area that would result
in removal of the earth-concrete dam would permit invasion by G.
affinis thus eliminating G. heterochir (07).
The Clear Creek gambusia habitat is obviously dependent upon a
Management Practices - 2 (DRAFT) - Management Practices
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
reliable and substantial supply of spring water; therefore, it is
essential that the Edwards-Trinity Aquifer recharge zone remain
undisturbed. Most of the local recharge zone appears to be in
ranchland north and west of the headspring.
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1982. Clear Creak Gambusia Recovery
Plan. U.S. Fish and Wildlife Service, Albuquerque, New Mexico.
29 pp.
The primary objective of the Recovery Plan is to improve the
status of the Clear Creek gambusia (Gambusia heterochir) so that it
may continue to survive in and near the headsprings of Clear Creek,
Menard County, TX. The principle concern of the plan was that, since
the area is privately owned and was for sale at the time of writing
(1980), the USFWS acquire management rights to the gambusia habitat.
This was not accomplished before the sale. If a similar opportunity
arises in the future, it may be desirable to aquire the land and/or
water rights. Fortunately, the owner has been very helpful and
concerned about the gambusia and management of the springs for the
species benefit continues. Protection of the habitat including the
headspring pool and aquifer recharge zone (maintaining waterflow and
controlling development) is important due to the limited distribution
of the Clear Creek gambusia. If the entire stream is also protected
it may be beneficial to revert the entire 5 km of stream back into
a spring run habitat by removing dams. The extensive exposed mudflats
that would be left by dam removal should be seeded to prevent erosion.
Understanding the biology and ecology of the Clear Creek gambusia
is also a high priority. Recommended research includes:
1) Studies of competition between the G. heterochir and G.
affinis.
2) Studies of prey species of the G. heterochir.
3) Studies of reproductive variables.
4) Studies of predation on the G. heterochir.
5) Studies of survivorship.
6) Studies of diseases and parasites.
Since maintenance and enhancement of existing habitat is critical
to the species survival; the physical, chemical, and biological
features of the habitat should be studied in relation to species
abundance. The controlling of herbicide and pesticides known to be
detrimental to this species in the immediate area and the restricting
of development may help maintain the integrity of the habitat.
Management of Clear Creek above Dam 1 requires maintaining its
integrity to stop further immigration of G. affinis into Clear Creek
gambusia habitat. Repairs to Dam 1 in 1979, which again separated the
majority of the G. affinis population from the G. heterochir habitat,
was an important step in this process. Current plans by the new owner
to reconstruct Dam 1 with USFWS technical assistance are encouraging.
These modifications and management steps will help to maintain the
water flow. Management for Clear Creek gambusia should also include
monitoring populations 2 to 4 times annually. Captive populations
should be maintained at Dexter NFH for scientific research and
Management Practices - 3 (DRAFT) - Management Practices
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
reintroduction. The Clear Creek gambusia should be provided the full
protection mandated by Federal and Texas laws. Finally, public
awareness of the uniqueness of the Clear Creek gambusia should be
increased through the preparation of information pamplets and news
releases.
Management Practices - 4 (DRAFT) - References
Species GAMBUSIA, CLEAR CREEK
Species Id ESIS252005
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Hubbs, C. 1957. Gambusia heterochir, a new Poeciliid fish from
Texas with an account of its hybridization with Gambusia affinis.
Tulane Stud. 5:1-16.
02 Minckley, W.L. 1962. Two new species of fishes of the genus
Gambusia (Pieciliidae) from northwestern Mexico. Copeia
1962:391-396.
03 Rosen, D.E. and R.M. Bailey. 1963. The Poeciliid fishes
(Cyprinodontiformes), their structure, zoogeography, and
systematics. Bull. Amer. Mus. Nat. Hist. 126:1-176.
04 Rivas, L.R. 1963. Subgenera and species groups in the Poeciliid
fish genus Gambusia Poey. Copeia 1963:331-347.
05 Peden, A.E. 1973. Variation in anal spot expression of gambusine
females and its effect on male courtship. Copeia 1973:250-263.
06 Hubbs, C. 1971. Competition and isolation mechanisms in the
Gambusia affinis x G. heterochir hybrid swarm. Bull. TX Mem. Mus.
19:47 pp.
07 U.S. Fish and Wildlife Service. 1980. Clear Creek Gambusia
(Gambusia heterochir) Recovery Plan. U.S. Fish and Wildlife
Service, Albuquerque, NM. 29 pp.
08 Rhode, F.C. 1980. Gambusia heterochir Hubbs Clear Creek gambusia.
In: Atlas of North American freshwater fishes. D.S. Lee, et al.
543 pp.
09 Hubbs, C. 1959. Population analysis of a hybrid swarm between
Gambusia affinis and Gambusia heterochir. Evolution 13:236-246.
10 Hubbs, C. 1982. Occurrence of exotic fishes in Texas waters.
Pearce-Sollards Series, TX Mem. Mus. 36. 19 pp.
11 Edwards, R.J. and C. Hubbs. In press. Temporal changes in the
Gambusia heterochir x G. affinis hybrid swarm following dam
reconstruction. Endangered Sp. Rep. USFWS, Albuquerque, NM.
12 Stevenson, M.M. and A.E. Peden. 1973. Description and ecology of
Hyalella texana n. sp. (Crustacea:Amphipoda) from the Edwards
Plateau of Texas. Am. Midl. Nat. 89:426-436.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Hubbs, C. 1971. Competition and isolation mechanisms in the
Gambusia affinis x G. heterochir hybrid swarm. Bull. TX Mem. Mus.
19:47 pp.
02 Edwards, R.J. and C. Hubbs. In press. Temporal changes in the
Gambusia heterochir x G. affinis hybrid swarm following dam
reconstruction. Endangered Sp. Rep. USFWS. Albuquerque, NM.
03 U.S. Fish and Wildlife Service. 1980. Clear Creek Gambusia
(Gambusia heterochir) Recovery Plan. U.S. Fish and Wildlife
Service, Albuquerque, NM. 29 pp.
References - 1