Invasive fish species raise river concerns

An exotic, armored fish that can grow to two feet long threatens to disrupt the ecosystem of the San Marcos River.

The Suckermouth Armored Catfish (Hypostomus Plecostomus) destabilizes shores, eats the eggs of endangered species, and is available at most aquarium stores, says Dr. Timothy Bonner, Ph.D. Director and Professor of Aquatic Biology at Texas State University.

“You buy them small,” Bonner said. “What they like to do is eat algae, so you can put them in your tank and they’ll stick to the side of the tank and they’ll eat the algae.”

While the catfish can be useful in the short term, “whenever they get big — and they get big — they outgrow their aquarium, and people tend to get rid of them,” Bonner said.

According to Bonner, 14 non-native species of fish are currently swimming through San Marcos waterways, including the Suckermouth Armored Catfish.

Bonner gave two reasons why he thinks San Marcos is home to several non-native fish species.

One of those reasons is the ponds in front of the Freeman Aquatic Biology building in the state of Texas, which were formerly part of the National Fish Hatchery system built in the early 20th century.

The other reason is the dumping of fish tanks, which Bonner attributes to the large student population of San Marcos.

“They’re moving within a few years, and I think that might increase the chances of those fish being dumped in the river, which again is illegal, but people are thinking more about the concept of free will,” Bonner said.

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According to Kristy Kollaus, environmental scientist for the Edwards Authority Habitat Conservation Plan (EAHCP), Suckermouth Armored Catfish are considered successful invaders for a few important reasons.

“They have this armor, so really big armor that makes it hard for predators to eat them,” Kollaus said. “Outside of their natural range, they have no known predators, so there’s nothing they’re actively consuming or feeding on to keep their numbers down.”

Suckermouth Armored Catfish also threaten the Fountain Darter, an endangered species identified in the EAHCP.

The US Fish and Wildlife Service requires municipalities to introduce HCPs. Each year, the City of San Marcos receives EAHCP funding for the management of invasive alien fish and plants.

Funding for the EAHCP program comes from fees due to groundwater abstraction permit holders from Edwards Aquifer, according to Mark Enders, habitat conservation manager at San Marcos’ CIP/Engineering Department.

On Tuesday, December 6, the San Marcos City Council renewed its contract with Atlas Environmental, Inc. for the removal of aquatic invasive fish and snails for an annual amount of $16,200.

The contract with Atlas has been in force since 2013. As of May 31, Atlas has removed 12,537 catfish from the Upper San Marcos River and Spring Lake.

Kollaus said what researchers from the EAA, Meadows Center and Texas A&M are working on is “implantation[ing] Tags, those radio sonar tags in armored catfish to see if we can figure out where they congregate their population so we can improve our efforts,” he added, adding that gene editing might also be a possibility later on.

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While the city is not currently considering an ordinance banning the sale of aquarium fish, Texas residents and students can drop off their unwanted aquarium fish at the city’s Discovery Center.

“This provides a safe, humane option for people who want to properly dispose of their aquarium fish without having to release them [them] into the river system,” Enders said.

Visit https://www.sanmarcostx.gov/2798/Pet-Fish-Drop-Off-Adoptions for more information.

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