Whether it’s in a casserole or a fish cake, people love their tuna, both canned and fresh. But the two differ in nutritional value, smell and taste. According to the Tuna Council, canned tuna is the most popular seafood product in the United States after shrimp, and tuna represents more than 1/3 of the total fish and seafood segment in the country. Both contain traces of mercury.

Good canned tuna is firm and flaky. An oily fish, tuna is high in Vitamin D and omega-3 fatty acids.

Good fresh tuna steaks look a lot like beef steaks, ranging in color from light pink to deep red, and the texture is very much the same. Tuna with dry or brown spots is not fresh.

When cooked properly, fresh tuna has better nutritional value than canned tuna. It is higher in fatty acids. During the canning process, however, tuna can lose many of the values of fatty acids fresh tuna has.

Although canned tuna doesn’t have quite the same taste or texture as fresh tuna, one can be substituted for the other, particularly with the ever-popular tuna salad.

The Food and Drug Administration issued in 2004 guidelines recommending that “pregnant women, nursing mothers and children limit their intake of tuna.” This is because nearly all fish contain some traces of mercury, which can be particularly harmful to infants and small children.