SAN ANTONIO – A new study out of the University of Texas at San Antonio is shedding light on how climate change is already impacting local waterways, and what that could mean for people across South Texas.
A UTSA researcher is tracking tropical fish in local streams — fish that couldn’t survive here before — what their movement says about warming temperatures, water quality and the future of Texas rivers.
Matthew Troia, UTSA assistant professor in the Department of Biology, Health and Environment, said rising temperatures in San Antonio’s rivers and streams are allowing tropical fish to survive in places they couldn’t before.
“So climate change, so just increasing air temperatures, is causing the water temperature to increase,” Troia said. “There’s an urban heat island effect happening. All those things are probably contributing to these fish being able to do well in these streams.”
Troia has been tracking water temperatures in Central Texas since 2019, studying how fish respond to a changing environment. With new funding from the National Science Foundation, his research is now focusing on how freshwater tropical fish — often found in places like the Amazon — are now surviving in local waterways.
Some of those fish, he said, may have originally been released into the wild.
“It’s not a coincidence that a lot of the tropical fish are like pet store fish,” Troia said.
While tropical fish moving into local streams may seem harmless, Troia said it could come at a cost, especially for native species.
As new species move in, native fish can be pushed out, disrupting ecosystems that have existed for generations.
“The Guadalupe bass, for example, only occurs in Texas, so it’s endemic, but it’s a very popular recreational species,” Troia said. “People like to go up into the Hill Country and catch those fish. And so if you told a lot of anglers throughout Texas, ‘Hey, in 20 years, we’re not going to have Guadalupe bass anymore,’ How would you feel about that?”
He said those changes don’t just impact wildlife — they can also affect water quality and, ultimately, people.
“If you have a completely different group of species doing different things, that can have ramifications for water quality, bacterial loads in the streams, nutrients, things that more directly affect people,” Troia said.
Researchers said what’s happening in San Antonio streams is a real-time warning that environmental changes don’t stay isolated.
As ecosystems shift, the impacts can ripple outward, affecting water quality, wildlife and the health of communities that depend on these waterways every day.
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