Tosefta for Chullin 225:50

Unclean fish that was pickled with clean fish: He washes [the clean fish] thoroughly and it is permitted. Unclean salted fish and clean unsalted fish: It is forbidden. Clean salted fish and unclean unsalted fish: It is permitted. Unclean fish that was cooked with clean fish: We treat it as though [the clean fish was cooked with] leeks (see Hul. 97b:8) -- if there is sufficient quantity to impart taste, it is forbidden, and if not, it is permitted.