Asian carp are the exotic fish species that we hear the most about, but plenty of others are established in our waters as well, mostly because of an under-regulated exotic pet industry and irresponsible aquarium owners. Clinton Richardson recently caught this unusual catfish while fishing the lower Susquehanna River. Biologists identified it as a hybrid catfish from the aquarium trade, a cross between a redtail catfish and a tiger shovelnose catfish. Both grow large in their native South America.
"Irresponsible aquarium owners continue to introduce exotic and at times invasive fish to our waterways when their pet fish become too large or they tire of them," noted the Maryland Department of Natural Resources. "The introduction of the northern snakehead is a perfect example."
The big question now is whether climate is too cold for such exotic catfish to establish breeding populations that far north, if they haven't already.
In Florida, meanwhile, the suckermouth armored catfish, also from South America, is firmly entrenched over much of the peninsula. And almost certainly it came from the aquarium trade as well, as it often is labeled a "plecostomus" or "algae eater."
The burrows that they make for spawning likely cause or exacerbate erosion on shorelines of canals and rivers, although no quantitative data is available on that. Additionally, they have been observed browsing on the algae that frequently grows on the backs of manatees.
"Manatee responses varied widely; some did not react visibly to attached catfish whereas others appeared agitated and attempted to dislodge the fish. The costs and/or benefits of this interaction to manatees remain unclear," said the U.S. Geological Survey.