The purpose of marinating most meat is twofold. First, marinades add flavor. Secondly, the acids, such as lemon or lime juice, tenderize a tough cut of meat. Because fish already is tender, do not leave it in an acid-based marinade for more than one hour. The acid literally will cook the fish without heat. When overly marinated fish is then cooked, it becomes mushy and has a tendency to fall apart. There is a simple way to infuse your fish with flavor while avoiding this potential pitfall when marinating overnight.
Inspect the fish for any bones and remove if them if necessary.
Rinse the steaks or fillets briefly under cold water and pat dry with a paper towel.
Spray the fish with a coating of cooking spray or massage lightly with extra virgin olive oil. This prepares the fish to receive your marinade.
Sprinkle the oiled fish with an herb or seasoning blend of your choosing. This method is called a dry marinade in contrast to a wet marinade that typically has an acid base. Sprinkle with salt and pepper if desired.
After applying a generous coating of the seasoning you choose, rub the fish gently to work the flavors into the individual pieces.
Place the fish in a large resealable storage bag or container. The pieces do not need to be in a single layer. If the pieces overlap, it simply exposes them to more of the dry marinade.
Refrigerate, preferably no longer than 24 hours. Cook the marinated fish as desired.