Biwa trout; Biwa salmon
A subspecies of masu salmon endemic to Lake Biwa in Shiga Prefecture, Japan. Often treated as a regional delicacy.
ビワマスは琵琶湖だけに生息する固有種です。
The Biwa trout is an endemic species found only in Lake Biwa.
春になるとビワマス漁が解禁されます。
Fishing for Biwa trout opens in spring.
Katakana spelling is standard for this fish name.
Kanji spelling is rare; the word is usually written in kana.
From 琵琶 (Biwa, referring to Lake Biwa) + 鱒 (masu, trout/salmon). The exact derivation is straightforward; the name reflects its habitat.