Cooked to perfection, fish is at its flavorful best, will be moist, tender and have a delicate flavor. In general, fish is cooked when its meat just begins to flake easily when tested with a fork and it loses its translucent or raw appearance. Like most foods, fish should be thoroughly cooked.
One helpful guideline is the 10-minute rule for cooking finfish. Apply it when baking, broiling, grilling, steaming and poaching filets, steaks or whole fish. (Do not apply the 10-minute rule to microwave cooking or deep frying.)
The 10-minute rule:
1. Measure the seafood product at its thickest point. If the fish is stuffed or rolled, measure it after stuffing or rolling.
2. At 450 degrees F, cook it 10 minutes per inch thickness of the fish, turning the fish halfway through the cooking time. For example, a 1-inch fish steak should be cooked 5 minutes on each side for a total of 10 minutes. Pieces of fish less than 1/2-inch thick do not have to be turned over.
3. Add 5 minutes to the total cooking time if you are cooking the fish in foil or if the fish is cooked in a sauce.