noun
red-spotted masu salmon; sea-run masu trout
Refers specifically to the sea-run (anadromous) form of the cherry salmon subspecies Oncorhynchus masou ishikawae, known as アマゴ (amago) when landlocked. The term is used in fisheries and regional cuisine.
See also: 甘子
サツキマスはアマゴが海に下ったものです。
The satsukimasu is an amago that has gone down to the sea.
この川では春にサツキマスが釣れます。
In this river, you can catch satsukimasu in spring.
The name サツキマス literally means 'May trout' (皐月 is an old name for May, 鱒 means trout), referring to the season when it returns to rivers. The exact historical derivation is uncertain.