In which river basin is this large-toothed fish to be found?

This is the goliath tigerfish or giant tigerfish, known formally as “Hydrocynus goliath” and known colloquially as M’benga. “M’benga” is a word in the local African language of its habitat, and it means “dangerous fish.”

It is dangerous. This very large, highly predatory fish grows to a length of 1.5 metres (4 ft 10 inches) and a weight of 50 kilograms (110 lb). Its teeth fit into distinct grooves along its jaws and each of the teeth can grow up to 2.5 centimetres (1 inch). The largest recorded specimen weighed 70 kg (154 lb). M’benga is the largest member of the family “Alestidae” and this species of tigerfish lives only in the Congo River basin in Central Africa, in a region known as west equatorial Africa.

M’benga’s feeding habits are simple: it will take any fish it can overpower, including smaller members of the same species. When hunting, this fish uses the calmer eddies of the rapids to ambush its prey, using its keen sight to detect prey. When a target is noticed, the fish accelerates to chase it down. There have been incidents reported in the Congo of M’benga attacking humans. This reputation, combined with its great strength, has accorded it an almost mythical status among anglers.

The mature M’benga has only one known natural predator: the Nile crocodile.