Tuna is a saltwater fish with oily, flavorful, meaty flesh that ranges in color from pale to dark, depending on the species. Tuna is sold as fillets or steaks, which are available fresh or frozen. American brands of canned tuna are generally packed in water or vegetable oil. Italian tunas are packed in olive oil, which gives the fish a more complex flavor.
To test fish for doneness:
Slit the fillet or steak at the thickest part with the tip of a small, sharp knife. If properly cooked, the flesh will appear just opaque but still moist.For other types of fish, see anchovies, cod, flounder, halibut, lingcod, mackerel, monkfish, red snapper, rock cod, salmon, salt cod, sardines, sea bass, snapper, sole, swordfish, and trout.