From the Greek kata... - prefix meaning movement from top to bottom, drómos meaning running and Latin migratio meaning transition, migration.

Long-distance migrations of fish are usually divided into anadromous (from the sea to the coasts and further up the rivers) and catadromous (in the opposite direction).

Catadromous migrations are movements of fish for spawning from the upper reaches of rivers to the lower reaches, from rivers to the sea (eel), from coastal areas to the open sea. Some Galaxiidae and Gobiidae make catadromous spawning migrations, much shorter than eel.

The most striking representative of catadromous species is the eel family (eel). Its eggs can travel in the open ocean for months and even years. Then they are carried to European shores, where they swim into rivers and begin their development. Eels like strong currents, muddy or sandy soil. It is very difficult to spot it, during the day it hides in burrows or under rocks. With the onset of night, he comes out of his shelter. The European eel spends most of its life in freshwater environments.