Silurus biwaensis

Silurus biwaensis, the giant Lake Biwa catfish, is a large predatory catfish species endemic to Lake Biwa in Japan.

Description
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 1.18 m in length and weigh as much as 17 kg. 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.

Relationship to humans
Some fishermen believe that the catfish change their behavior and become very active when an earthquake is imminent. In Japanese mythology, a giant catfish named Namazu causes earthquakes as he moves below the Earth's surface.