The Walking Catfish, Clarias batrachus, is a very large catfish sometimes seen in the aquarium trade. It is also used as a food fish. It is native to Southeastern Asia, but it has been introduced to numerous other places where it has become an invasive and predatory pest. Once in an area, it is hard to contain because it can walk across land, entering aquaculture ponds and eating the fish, or entering seasonal wetlands not normally inhabited by fish to eat tadpoles.
It has been introduced to Indonesia (Sulawesi), the USA, Hong Kong, Taiwan, China, UK, Papua New Guinea, Guam, Taiwan, Thailand, and possibly the Philippines. This species has been nominated as one of the world’s top 100 invasive species. The method of invasion involves escapees from the pet trade as well as aquaculture. It is illegal to keep this fish in some countries, as well as in many US states.
Very cold water kills Walking Catfish, so if your area goes below freezing in the winter this fish should not become invasive even if some manage to escape. In many areas with warmer water it is often illegal to keep them without a permit. Even if they are legal in a warmer area, it is still very important not to let them escape from their tank. Because of their ability to walk on land, the possibility of escape is much greater than with most tropical fish. Make sure their aquarium has a strong and tightly fitting lid so that they cannot push it up and wander off.
Global invasive species database. Compiled by Invasive Species Specialist Group (ISSG)
Brogan, Christine. 2003 Introduced Species Summary Project