Lingcod is one of my favorites as well even months after frozen. Was fortunate to bring home twelve of 'em this year. With a sharp thin knife, trim the pinkish-grayish fat off the skin side of the previously frozen fillets prior to cooking. It doesn't hold up well in the freezer. I'll even trim them prior to freezing. No amount of seasoning/marinating/cooking/recipe, etc, will make the flavor of that fat line go away. Kinda like what you'd do to a sturgeon.