Asterophysus batrachus, the gulper catfish or ogre catfish, is a species of catfish (order Siluriformes) of the family Auchenipteridae. It is native to the Rio Negro and Orinoco basins in Brazil, Colombia and Venezuela, where mostly found in slow-moving waters with many submerged structures. It is currently the only recognized species of the genus Asterophysus, but a specimen that possibly represents an undescribed species has been collected in Marajó (about from the traditionally recognized range of A. batrachus). The gulper catfish grows to a standard length of , and a total length of . It has a short, thick-set shape and is dark-colored with a whitish belly. People in its native range typically will not eat it because they consider it very ugly, but it is sometimes kept in aquariums. Feeding The gulper catfish is a strict carnivore and swallows its prey, mostly other fish, whole. This prey can be exceptionally large for its size, sometimes even larger than the gulper catfish itself, although such feeding attempts can be unsuccessful. The catfish catches prey by swimming slowly up to it and opening the huge mouth over its frontal part (head section). Escaping out of the mouth is generally prevented by the fine, backwards-pointing teeth of the catfish. Instead the prey attempts to escape by swimming into the mouth only to become further engulfed and eventually ending up folded (with both its head and tail pointing towards the predator's head) in the greatly extendable gulper catfish stomach. The fully extended stomach may result in an abnormal appearance of the gulper catfish to the point where its swimming can be impaired. It may also swallow large amounts of water only to expel it later along with remains of earlier prey. Potential prey fish like cichlids are apparently unable to recognize the gulper catfish as dangerous until it is too late. This is because of the catfish's size (prey fish will not generally consider other fish of roughly similar size as a major threat) and its slow, unobtrusive approach. Even if the first attempt fails because the prey manages to struggle free, the gulper catfish will not try to pursue it. The prey will typically still not realize that the catfish represents a threat and can be eaten using the same slow approach again. Another method of catching prey was observed by a snorkeler in the Atabapo River. Here the gulper catfish live