catadromous fish
Technical term in biology for fish that migrate from freshwater to the sea to spawn, such as eels. Contrasts with 遡河魚 (anadromous fish).
See also: 遡河魚
The eel is a typical example of a catadromous fish.
Catadromous fish migrate downstream from rivers to the sea to spawn.
Compound of 降 (descend) + 河 (river) + 魚 (fish), literally 'descending-river fish'. The exact historical derivation is uncertain, but the term is a modern biological coinage.