The giant Lake Biwa catfish is very similar to wels catfish, which it is closely related to. It has an elongated cylindrical body and can reach up to in length and weigh as much as. The top of the body is dark grey to black in colour while the underside is a pale, whitish colour.
Life cycle
They prey on fish and frogs which live in the lake. S. biwaensis is the largest predatory fish in Lake Biwa. Using telemetry methods researchers tried to explain the migratory behavior of the species. It was found that the fish are more or less site-faithful and mostly stay close to their spawning grounds. Other studies have shown that the sub-populations of the lake hardly mix.