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Implications of local San Marcos fish species loss

Wednesday, November 1, 2023

A highly specialized fish, home to only San Marcos, was recently removed from the Endangered Species List and classified as extinct. The protections on the San Marcos River, springs as well as Spring Lake, will not be removed due to the loss of the local Gambusia. According to the Meadows Center for the Water and Environment website, the Upper San Marcos River is one of the most biologically diverse ecosystems in the southwestern U.S. that still contains seven endangered species.

The Meadows Center for Water and the Environment Director of Operations Carrie Thompson said the San Marcos Gambusia was a small fish that was unique in that it gave birth to live fish.

“There are other fish like it in the river that people know as mosquito fish,” Thompson said. “But this one was highly specialized and was only found here in a small portion of the river.”

Thompson said the San Marcos Gambusia has actually been gone for approximately 40 years. Due to the processes at the federal level involved in removing a species from the endangered list, it has only recently been labeled extinct.

“The U.S. Fish and Wildlife Service … did some extensive surveys on the river beginning in the 1990s,” Thompson said. “They also tried to breed it in captivity, and they were unable to do that. … They just weren’t getting any new information or any evidence that the species was ever found again.”

Specifically, Thompson said academic researchers, Texas Parks and Wildlife Department scientists and the U.S. Fish and Wildlife Service have searched for the San Marcos Gambusia during all collection and research with fish on the San Marcos River. San Marcos Gambusia have not been found in the wild since 1983, including the searches conducted in May, July and September of 1990, which covered the species’ known range and designated habitat. Since 1996, all attempts to locate and collect San Marcos Gambusia have failed.

“It’s just a reminder that everything we do here has impacts,” Thompson said. “It’s really important that we continue to take good care of this ecosystem that supports this really special place and these really special species.”

The Meadows Center website said there are seven known species listed as threatened or endangered by the U.S. Fish & Wildlife Service and Texas Parks and Wildlife Department that still reside in the San Marcos region of the Edwards Aquifer, Spring Lake and the upper four miles of the San Marcos River, and those include the Comal Springs Dryopid Beetle, the Fountain Darter, the Peck’s Cave Amphipod, the San Marcos Salamander, the Texas Blind Salamander, Texas wild-rice and Comal Springs Riffle Beetle.

Learn more about the San Marcos Gambusia at this link species/sanmarcosgambusia/.

San Marcos Record

(512) 392-2458
P.O. Box 1109, San Marcos, TX 78666