While seafood that smells or tastes a little "fishy" isn't necessarily bad, there's an easy solution if you find it unpleasant.
Unless the fish or seafood you’ve bought is literally the catch of the day, chances are it will smell and taste at least a little fishy, thanks to a compound found in nearly all seafood called trimethylamine oxide, or TMAO. This compound is odorless when fish and shellfish are alive, but once they’re killed, TMAO slowly transforms into TMA (trimethylamine), which has a fishy odor. But that doesn’t mean that the seafood has gone bad or is unusable. We’ve found an easy way to eliminate the smell: Soak the fish or the shellfish meat in milk for 20 minutes and then drain and pat dry. The casein in milk binds to the TMA, and when drained away, it takes the culprit that causes fishy odor with it. The result is seafood that’s sweet smelling and clean-flavored.