Conservation

Tiny San Marcos River Fish Is Declared Extinct

Time has run out for the San Marcos gambusia. The fish, found only in the upper reaches of the San Marcos River, was declared extinct by the U.S. Fish and Wildlife Service in October, along with 20 other U.S. plants and animals. The fish was placed on the endangered species list in 1980 and was last seen and collected in the wild in 1983.

Originally described as a species in 1969, the San Marcos gambusia lived in the spring outflow of the San Marcos River. Possible causes for its extinction are habitat loss due to changes in vegetation, competition from introduced species and water overuse that depleted ground water and spring flow.
The San Marcos gambusia was very similar in appearance to the widely distributed western mosquitofish (Gambusia affinis). Adults were typically less than 2 inches in length and had a prominent dark stripe along the upper edges of the dorsal fin. They ate small invertebrates and gave birth to live young instead of laying eggs like many species of fish.

“It’s sad to see a Texas fish go extinct,” says Megan Bean, Texas Parks and Wildlife Department’s native fish conservation coordinator. “This species is part of our Texas heritage and is no longer part of what Texans can enjoy in the San Marcos River.”

Efforts to find the fish since 1983 were unsuccessful. “All available information and field survey data support a determination that the San Marcos gambusia has been extinct in the wild for more than 35 years,” the U.S. Fish and Wildlife Service says.

TPWD and other organizations are working hard to conserve other endangered species on the San Marcos River, including Texas wild rice, fountain darter, Texas blind salamander and others. TPWD designated the headwaters of the San Marcos River as a State Scientific Area and encourages responsible recreation on the river.
Clark Hubbs of the University of Texas at Austin, who first identified the San Marcos gambusia, recognized the unique nature of the San Marcos River. He stated the following in the July 14, 1980, Federal Register: “I have been involved in many studies of the biota of the San Marcos River. I have also had occasion to make similar observations on the biology of other waters and am convinced that the San Marcos is among our most unique ecosystems (worldwide). As a biological (and recreational) resource it has enormous financial and aesthetic value.”

Key partners in the conservation effort to preserve this unique and special place include the San Marcos River Foundation, Edwards Aquifer Authority, U.S. Fish and Wildlife Service, City of San Marcos, Guadalupe-Blanco River Authority and the Meadows Center for Water and the Environment at Texas State University.

“It is important for local municipalities, community partners and conservation groups to come together to protect the San Marcos River for Texans to enjoy now and for future generations,” Bean says. “It is encouraging to see partners working and coming together to protect the river, habitats and species that are still with us.”