Amphidromous migration

... The movement of fish between the sea and freshwater, as in the case of sweetfish, is called diadromous migration. Of these, fish that live and grow in the ocean, such as salmon and lamprey, and then enter freshwater to spawn are called anadromous migration, while fish that live in freshwater, such as eels, and then move down to the sea to spawn when they mature are called catadromous (or downriver) migration. In addition, fish that move between freshwater and the sea at certain times in their life cycle, unrelated to spawning, are called amphidromous migration in the strict sense. It is known that not only fish, but also whales, fur seals, king crabs, and squids migrate.

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

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…　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。　なお，魚類だけでなく，クジラ，オットセイ，タラバガニ，イカなども回遊をすることが知られている。…

※「amphidromous 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