Dolphin Catfish

About

Found across a wide sweep of South American river systems from Argentina north through Peru, Ecuador, Guyana, and Suriname, this marbled auchenipterid catfish, Ageneiosus marmoratus, goes by several names in the trade. Dolphin catfish, hammerhead catfish, and Guyana slopehead catfish among them. The head is large and robust with a notably broad, parabola-shaped snout and a wide gape that leaves little doubt about its predatory nature. Juveniles display a bold, high-contrast pattern of black blotches across the body that fades as the fish matures, though adults remain impressive in their own right. In the aquarium this species is best described as a conditional community fish. Anything small enough to fit in that mouth will eventually disappear, but with appropriately sized tankmates it settles in surprisingly well. It shows no real aggression toward its own kind and actually does better in groups of four or more. Good companions include peaceful substrate feeders like eartheaters, doradid and loricariid catfishes of comparable size, and larger characins. Reproduction has not been achieved in captivity in any documented way, though this species practices internal fertilization, a genuinely unusual trait in catfishes, using modified fin structures for courtship. Intermediate-level keepers with a suitably large tank and careful stocking plans will find it a long-lived and rewarding species.