Catadromous migration

…They enter rivers in late spring, when the water temperatures of the sea and river are almost the same. The movement back and forth between the sea and freshwater, as in the case of sweetfish, is called diadromous migration. Among these, the movement back and forth between the sea and freshwater, as in salmon and lamprey, is called anadromous migration, while the movement back and forth between the sea and freshwater, as in eels, is called catadromous migration. In addition, the movement back and forth between freshwater and the sea at certain times in their life cycle, unrelated to spawning, is called amphidromous migration in the strict sense. …

*Some of the terminology that refers to "catadromous migration" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…晩春，川に入るが，その時期は海と川の水温がほぼ同じになるときである。　アユのように海と淡水とを往復するのを両側回遊diadromous migrationというが，このうち，サケやヤツメウナギのように海洋で生活，成長し，産卵時に淡水に入るのを遡河回遊anadromous migration，ウナギのように淡水で生活し，成熟すると海へ産卵に下るのを降河(あるいは降海)回遊catadromous migrationと呼ぶ。このほか産卵と関係なく生活史の決まった時期に淡水と海とを往復するものを狭義の両側回遊amphidromous migrationという。…

※「catadromous migration」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報