What You Should Know About Buying Canned Tuna

When it comes to tuna, most stories highlight the difference between light and white meat, oil-packed and water-packed, and that thorny mercury issue. But many writers eschew environmental issues, and although American tuna consumption has declined over the last decade, the industry is a 42 billion dollar powerhouse, and the tuna population around the world is becoming depleted.

We reached out to William Carvalho, co-founder of Wild Planet, whose tuna (sold at Whole Foods, Stop and Shop, and Hannaford, among others) is often at the top of sustainability rankings for canned tuna. He explained the different types of tuna and told us what to look for before plunking your go-to can in the cart.

“In general, albacore comprises over half” of what you’ll see in any grocery store, says Carvalho. “It’s the preferred tuna for the American taste profile. Albacore tuna, of course, is lighter in color and legally has to have a certain whiteness in order to be sold as white tuna.” He thinks a lot of folks like it because it’s a lot like chicken breast.

What’s sold as light meat, on the other hand, “is typically skipjack tuna,” Carvalho says. It has less fat, and is fishier-tasting. Know this, though: “’Light tuna’ can have not just skipjack but also yellowfin and any number of other numbers of species on the label,” he warns. “Unless the brand discloses [it], in light tuna you don’t know what species you’re getting.” (Carvalho obviously has an incentive to recommend his own tuna, but notes that he discloses the genus and species contained in every can Wild Planet sells.)

Often tuna companies will cook the whole fish before canning it, which Carvalho says tends to dry it out. “In that cooking process—like any meat—there’s a tremendous amount of dripping going on, and the drippings contain a large part of the fats that naturally occur in the fish. The fats fall to the floor … now that omega 3 can’t find its way into that tuna because it’s gone.”

He says that his tuna and some other brands, on the other hand, are packed right into the can as they are and only cooked once, with a little bit of salt, to sterilize it, and it thus is preserved in its own oils. He says that his tuna doesn’t need mayonnaise, nor does it need to be packed in water or oil, because all the oils stay right in the can. (If you’re buying the more common twice-cooked tuna, which is often packed in oil or water, it’s often simply a matter of preference.)

Watch: How to Make Simple Tuna Salad

Even food writers who have studied seafood sustainability in the past can be lured by fancy Italian oil-packed tuna with a cool label, and forget what they’ve learned. But there are ways to find out not only what sort of tuna is in the can or on the sushi menu—the Monterey Bay Seafood Watch site is a well-regarded resource for finding out which varieties are endangered and which are not—but also how it’s caught.

The nomenclature is tricky: “In sustainable consideration, the most important word is selective,” says Carvalho. “Is this fishing selective or indiscriminate? If it’s indiscriminate and killing a certain portion of the ocean web … this planet cannot stand up to that.” He went on to explain the distinctions.

“‘Pole and line’ and ‘trolling’ are the two highest-rated methods,” says Carvalho. The former involves “One fish, one man, one hook,” in which a fisherperson snags “only the targeted species with the very rare exception.” “Troll” fishing, on the other hand, involves moving a motorized boat through water with a few poles out. The lures move in the water, fish see the lures moving, and they bite. (“Troll” shouldn’t be conflated with “trawl,” says Carvalho, which entails a big net—what he calls “the ‘Finding Nemo’ net.”)

Then there’s the confusingly named “long line” technique. It might sound straightforward and environmentally sound, but is widely regarded as detrimental. Long lines are fishing lines submerged in the ocean. (Carvalho says the style was referenced in The Perfect Storm.) These lines can run dozens of miles along the ocean floor, studded with hooks. “Anything will get hooked,” says Carvalho. Think: turtles, sharks, sunfish, and all sorts of “different fishes that are not the target,” he says. They’ll die, submerged in the water, and are discarded when the whole line is brought up.

“The real problem,” he says, “is often [vendors] call that long line fishing ‘line-caught.’” He suggests you avoid cans bearing the term “line-caught” at all cost. “It conflates the two fishing methods into one term; pole-and-line-caught is entirely different from a 50-mile long killing line.”

Finally, there’s the “purse seining” method, in which an entire school of migrating tuna is caught in a weighted net. In the 80s and 90s, says Carvalho, fishermen started noticing that schools would pause under floating piles of seaweed, feeling protected by the shadow, and they’d deploy their nets around the pile of seaweed. This was not ideal, says Carvalho, in that tiny baby tuna are among these schools, and sometimes other species of fish will get caught in the net, too.

But worst of all, he said, is that commercial fisheries have started deploying their own fake “floating seaweed,” called FAD, for “fish aggregating device.” A huge floating device attracts tons of fish of all species underneath. Fishermen will circle the entirety, pull it all up on to the boat, and bring it up. “Whatever they want to keep, they keep,” he says, but fish suffocate in the big nets. “Those guys are throwing 20 to 30 percent of everything they catch—millions of pounds of fish—in the ocean overboard dead.”

How does this affect you in the grocery store? “Most tuna that says ‘light meat tuna, 10 for a dollar’—if that tuna doesn’t say ‘pole and line caught’ it was certainly the FAD caught method and that’s why it’s sold cheap,” says Carvalho. “Cheap tuna comes at a very high environmental price.”

You need to be aware of the mercury content of tuna, whether canned or sold as sushi, especially if you’re expecting a baby. Reach out to your medical professional to learn more or do the research online, but some would say you should eat no more than a can of albacore, which contains more mercury than light tuna, weekly. (Some quibble with the FDA’s official positions on this issue.)

Tuna: It sure is more complicated than making a tuna melt, but it remains delicious.

Alex Van Buren is a food and travel writer living in Brooklyn, New York whose work has appeared in Gourmet.com, Bon Appétit, Travel + Leisure, New York Magazine, Martha Stewart Living, and Epicurious. Follow her on Twitter and Instagram @alexvanburen.