noun
sweetfish going downstream to spawn in autumn
Refers to ayu (sweetfish) that descend rivers to spawn in the lower reaches or sea during autumn. A seasonal term often used in fishing and culinary contexts.
秋になると、川で落ち鮎がよく釣れる。
In autumn, sweetfish going downstream to spawn are often caught in the river.
落ち鮎は産卵のために川を下る。
Sweetfish going downstream to spawn descend the river to lay eggs.
鮎 is the general term for sweetfish, while 落ち鮎 specifically refers to those migrating downstream to spawn in autumn.
Compound of 落ち (ochi, 'falling' or 'descending', the continuative form of 落ちる) and 鮎 (ayu, 'sweetfish').