Big Bend Gambusia (Gambusia gaigei)

Texas Status

Endangered

U.S. Status

Endangered, Listed 3/11/1967

Description

The Big Bend gambusia is about 2 inches in length.

Life History

Aquatic invertebrates form the Big Bend gambusia's diet. It bears live young.

Habitat

Clear, shallow spring-fed natural pools and marshes provide habitat for the Big Bend gambusia.

Distribution

Big Bend gambusia occur only in Big Bend National Park in west Texas .

Other

The Big Bend gambusia is known only from spring habitats near Boquillas Crossing and Rio Grande Village in Big Bend National Park. The population at Boquillas Spring died when the spring stopped flowing in 1954. The population near Rio Grande Village drastically declined between 1954 and 1956, after the spring flow was altered to provide a fishing pool. By 1960, the Big Bend gambusia could no longer be found at the Rio Grande Village location. The loss of this population was probably due to competition with the western mosquitofish and predation by the introduced green sunfish.

The only wild population exists in a protected pond located in Big Bend National Park. All present populations of Big Bend gambusia consist of descendants of three fish (two males and one female) taken from the declining Rio Grande Village population in 1956. The major threats to Big Bend gambusia and other desert spring fishes include habitat loss from declining spring flows and reduced surface waters, competition with introduced species, and hybridization with introduced fishes.