Overview
Clear Creek gambusia are only known from Clear Creek, and have never been observed beyond the headwaters of that creek and just below the uppermost dam, which is located in the headwaters area. Its current status in the wild is unknown. Clear Creek gambusia were observed in 2015, but a search effort in 2021 and 2022 using dip nets and minnow traps did not yield any apparent Clear Creek gambusia. If they are extant in the wild, their numbers are very low. The species was kept in captivity and propagated at Inks Dam National Fish Hatchery beginning in 2011. The fish were all moved to the San Antonio Zoo in 2024. As of 2025, fewer than 100 are in captivity.
Historically, Clear Creek was free-flowing until its confluence with the San Saba. It now contains a series of dams. Any extant Clear Creek gambusia are likely confined to the uppermost portion of the creek, above the highest dam and potentially just below it. The uppermost dam has been in disrepair since at least 2008, which has compromised the habitat conditions to which Clear Creek gambusia are adapted.
The Clear Creek gambusia was listed as endangered on March 11, 1967 (32 FR 4001). No critical habitat has been designated for the species. Five-year reviews were completed in 2010 and 2023.
Characteristics
Habitat
Clear Creek gambusia are spring-adapted and limited to the flowing, clear, stenothermal (constant temperature of about 20.8 ºC, 69.4 ºF), near neutral pH (7.1) waters of the spring outflows at the headwaters of Clear Creek. The springs are fed by waters from the limestone Edwards-Trinity (Plateau) Aquifer. They are found in association with an endemic amphipod (Hyalella texana) and plant (Ceratophyllum sp.). Clear Creek gambusia are most abundant near spring outlets and where aquatic vegetation is dense, typically around the periphery of the spring pool.
U.S. Fish and Wildlife Service. 2010. “Clear Creek Gambusia (Gambusia heterochir) 5-Year Review: Summary and Evaluation.� Austin, Texas: U.S. Fish and Wildlife Service.
Food
The endemic amphipod Hyalella texana is the primary food of the Clear Creek gambusia.
U.S. Fish and Wildlife Service. 2010. “Clear Creek Gambusia (Gambusia heterochir) 5-Year Review: Summary and Evaluation.� Austin, Texas: U.S. Fish and Wildlife Service.
Physical Characteristics
Hubbs described Clear Creek gambusia based on material collected from the headspring of Clear Creek, Menard County, Texas. Clear Creek gambusia are small, live-bearing Cyprinodontiform fish in the family Poeciliidae. Individuals of this species are stocky and have a metallic sheen with dark crescent-shaped marks on their scales. The size at sexual maturity is 25 millimeters (mm [0.98 inches (in)] in standard length for females, and 17 mm (0.67 in) in standard length for males. Clear Creek gambusia females have a pronounced anal spot. Males have several distinguishing characteristics, including a deep notch in the dorsal margin of the pectoral fin, and, compared to other Gambusia species, the largest gonopodial elbow and bluntest gonopodial tip.
Hubbs, Clark. 1957. �Gambusia heterochir, a New Poeciliid Fish from Texas, with an Account of Its Hybridization with G. affinis.� Tulane Studies in Zoology 5: 3�16. .
U.S. Fish and Wildlife Service and Rio Grande Fishes Recovery Team. 1982. “Clear Creek Gambusia Recovery Plan.� Albuquerque, New Mexico: U.S. Fish and Wildlife Service. Accessed from .
U.S. Fish and Wildlife Service. 2010. “Clear Creek Gambusia (Gambusia heterochir) 5-Year Review: Summary and Evaluation.� Austin, Texas: U.S. Fish and Wildlife Service.
Life Cycle
Clear Creek gambusia produce live young and are thought to have a prolonged reproductive season of at least seven. Females are able to store sperm. Fecundity is correlated with female body size and timing, highest in the largest females and peaking in August and September. The interbrood interval has been estimated at approximately 42-60 days, depending on temperature. Because of the long reproductive period, it is possible for females to give birth several times per year. Most individuals of the species live no more than one year. Females born in the spring are reproductive by the fall, and most young born in the fall are produced by females born earlier than same year. Because females may have multiple broods of many young in a single season, growth may be explosive when conditions are right. However, due to the short lifespan of the species, population crashes are also possible. Seasonal variation may be extreme, with populations highest at the end of summer and lowest in spring.
Hubbs, Clark. 1957. �Gambusia heterochir, a New Poeciliid Fish from Texas, with an Account of Its Hybridization with G. affinis.� Tulane Studies in Zoology 5: 3�16. .
——�. 1971. “Competition and Isolation Mechanisms in the Gambusia affinis X G. heterochir Hybrid Swarm.� Bulletin of the Texas Memorial Museum 19: 47.
Hubbs, Clark, and Doyle T. Mosier. 1985. “Fecundity of Gambusia Gaigei.� Copeia 1985 (4): 1063�1064. .
U.S. Fish and Wildlife Service and Rio Grande Fishes Recovery Team. 1982. “Clear Creek Gambusia Recovery Plan.� Albuquerque, New Mexico: U.S. Fish and Wildlife Service. Accessed from .
Geography
Clear Creek gambusia are only known from Clear Creek, which flows into the San Saba River in Menard County, west of the town of Menard. They have never been observed beyond the headwaters of that creek and just below the uppermost dam, which is located in the headwaters area.
Hubbs, Clark. 1957. �Gambusia heterochir, a New Poeciliid Fish from Texas, with an Account of Its Hybridization with G. affinis.� Tulane Studies in Zoology 5: 3�16. .
U.S. Fish and Wildlife Service. 2010. “Clear Creek Gambusia (Gambusia heterochir) 5-Year Review: Summary and Evaluation.� Austin, Texas: U.S. Fish and Wildlife Service.
——�. 2023. “Clear Creek Gambusia (Gambusia Heterochir) 5-Year Status Review: Summary and Evaluation.� Austin, Texas: U.S. Fish and Wildlife Service. Accessed from .
Timeline
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