Regarding the walking catfish...
Why they're called walking catfish:
An internal feature of the walking catfish that is of considerable note with regard to its ability to traverse short stretches of land is the suprabranchial arborescent organ. An extension of the apparatus that supports the fish's gill filaments, this structure facilitates the uptake of atmospheric oxygen by providing support for a number of gill filaments that would otherwise collapse in the absence of the buoyancy of water. In essence, this accessory air-breathing organ functions much like a lung. The branching appearance of this organ, reminiscent of a small tree, is the basis for the name "arborescent" organ.
Why you don't put them with other fish:
Walking catfish are benthic omnivores, industrious in their search for food. A nocturnal species, walking catfish search the bottom with their barbels vigorously sifting through detritus and soft substrates. A true generalist, walking catfish consume a wide variety of prey, including eggs or larvae of other fishes, small fishes, and a number of invertebrate taxa such as annelids, crustaceans, and insects. Given these somewhat indiscriminate feeding habits, it is not unusual to find a fair amount of detritus or plant matter in the gut this species. In densely populated drying pools, walking catfish are particularly indiscriminate in their choice of prey items, often seizing and consuming a wider variety of prey than what may normally be available.
Why you should never release aquarium fish into the wild:
Outside of its native range, the walking catfish is a demonstrated pest, with the potential to do severe ecological and economic harm. In response, numerous countries have "blacklisted" the walking catfish, including the United States, which has classified all members of the family Clariidae as injurious wildlife, illegal to possess without a federal permit.
In the United States, the history of the non-native population established in southern Florida during the early 1960's is well documented. The spread of the walking catfish from one or perhaps two points of introduction encompassed 20 counties in approximately 10 years; effectively the entire southern peninsula of Florida.
Source:
Florida Museum of Natural History Ichthyology Department
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