A qucik google seacrh for "pollck fish" found the following
Pollock is the common term for either of the two species in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P. pollachius include the Atlantic pollock, European pollock, lieu jaune, and pollack, while P. virens is sometimes known as the coalfish or saithe.
I also think coley may another laternative for coalfish/saithe
You didn't say how many letters in the answer.