We use to have a Super Bowl Fish fry and all would bring fish day or two before. Well you know some people don,t take care of there fish. Some freezer burnt, some not frozen in water, some just wanted to clean our there freezer. We always trimmed the freezer burnt part or dark blood line of fish But what always worked for us is to put about 1/4 cup mustard and one cup Beer or more mixed together, seasoned with seasoned salt, lots of Garlic powder mix seasoned fish with Beer and Mustard mix pack in gallon or quart freezer bag for at least 4 to 6 hours . Day before in refrigerator works best but can put in refrigerator for two days. No one could tell difference between old and fresh fish. Always a sucessful fun enjoyable fish fry. Cooking at right temp makes a difference also