trout

...Among them, the name "salmon" was used only for O. keta , a salmonid fish caught along the coast, which was large and had a large catch volume. The strict distinction between marine and freshwater fish has become weak. In foreign countries, Atlantic salmon ( Salmo salar ) was called "salmon" because it migrated to the sea, and brook trout ( S. trutta ) was called "trout" because it lived in lakes all its life. However, it has become clear that there are species of sea trout and brook trout that migrate to the sea, and those that live mainly in lakes and rivers are called "trout."

*Some of the terminology that mentions "trout" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…その中で，昔，沿岸で捕獲されるサケ科の魚の中では大きく漁獲量も多かったサケO.ketaのみが王者としてのサケの名を用いられ，海に生息するもの，淡水に生息するものとしての厳密な区分けは薄らいでいる。　外国では，海へ下るものとしてAtlantic salmon(Salmo salar)をsalmon，一生を湖でくらすものとしてbrook trout(S.trutta)をtroutと呼びならわしてきた。しかし，sea troutなどのように，またbrook troutでも海へ下るものがいることが明らかになり，湖川を中心に生息するものをtroutと呼んでいる。…

※「trout」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