And don't forget to label the bag with the name of the fish, how much is in the bag, and the date you are putting it in the freezer. Fatty fish like salmon will keep fairly well for 2 to 3 months, while lean fish stays longer‚Äîup to 6 months. But keep in mind the fish won't make you sick if kept longer, it just won't have as nice a flavor and texture. And the fresher it is when you freeze it, the better it will be when you thaw it.