yellowtail
鰤 refers specifically to the yellowtail fish, a type of amberjack important in Japanese cuisine.
鰤 is a phono-semantic compound: the left side 魚 (fish) indicates the meaning, while the right side 師 likely contributes the sound シ.
The left side is 魚 (fish), and the right side 師 can be thought of as a master or expert. Imagine a master fish chef selecting the finest yellowtail.
For シ, picture a yellowtail fish swimming in the sea: sea -> シ, and the fish is a prized catch.
Japanese amberjack (species of yellowtail, Seriola quinqueradiata)
black-banded trevally (Seriolina nigrofasciata); black-banded amberjack
yellowtail caught during the cold season; cold yellowtail
middle-sized Japanese amberjack (species of yellowtail, Seriola quinqueradiata)
rainbow runner (Elagatis bipinnulata); rainbow yellowtail; Spanish jack; Hawaiian salmon
pilot fish (Naucrates ductor)