The redtail catfish (Phractocephalus hemioliopterus), is a large species of South American pimelodid (long-whiskered) catfish. It is known in Venezuelan Spanish as cajaro; in Guyana, it is known as a banana catfish, and in Brazil it is known as pirarara, a fusion of words from the indigenous Tupi language: pirá and arara. It is the only extant species of its genus, Phractocephalus.

The redtail catfish is quite common in the aquarium trade, although it is often sold in its juvenile state, only measuring a few centimeters or inches at the time of sale. Additionally, they are often sold with little to no information for novice or uninformed buyers, with vague warnings, if any, regarding the fish’s massive adult size. Thus, many redtail catfish are sold and subsequently purchased as very small specimens, soon outgrowing their new aquariums—something which makes them highly unsuitable for all but the largest, usually public, aquariums (or outdoor stock tanks, pools, ponds, lakes, etc). Unfortunately, many have likely been purchased when young, by uninformed shoppers, and later released by these same individuals when their true size and voracity became evident. In this way, humans have directly contributed to the species’ spreading in areas outside of its natural range.

Hatchling (fry) and juvenile redtail catfish are most at-risk of being consumed by a range of predators, both aquatic and terrestrial. Larger adult specimens generally have little to fear, becoming voracious, opportunistic hunters themselves. Nevertheless, at any age or size, the redtail catfish is always at-risk of being consumed by humans, jaguars, giant otters, Orinoco and American crocodiles, and caimans, among other species.