Several weeks ago, a pre-teen girl fishing in Tom Bass Park in Houston, Texas hooked a piranha. According to the Texas Parks and Wildlife Department, it was likely an illegal pet that its owner tired of keeping. From the Houston Chronicle:
Fisheries managers worry prohibited species released into Texas waters will establish self-sustaining populations that could outcompete, prey on or otherwise overwhelm native species. Already, exotic invasive fish – armored catfish, tilapia and grass carp – have established self-sustaining populations in Texas, causing damage to freshwater ecosystems.
Piranhas, which have been documented in waterways in a dozen states, have not established populations where they have been found in North America. But that possibility exists if the fish are given enough opportunities through illegal releases.
Research indicates piranhas, evolved to live in consistently warm water, can't survive when water temperature drops below about 50 degrees.
But research presented by the American Fisheries Society indicates piranhas "might" be able to "overwinter" in waters in parts of the Deep South, including the southern third of Texas. The research indicates piranhas "could" live in winter in deep South Texas and most of Florida.
"Piranhas, other dangerous exotic species found in Texas' waterways"
