one fish; one shrimp
Counter for fish and shrimp, using the counter 尾 (び). Used when specifying exactly one fish or shrimp.
I bought one sea bream at the market.
This dish requires one shrimp.
一匹 is a general counter for small animals, including fish, but 一尾 is specifically for fish and shrimp.
Standard kanji spelling for counting fish and shrimp.
Compound of 一 (いち, 'one') and the counter 尾 (び, 'tail'), used for counting fish and shrimp.