How to pick out sustainable seafood.

Illuminating answers to environmental questions.
July 14 2009 9:28 AM

Green Herring?

Picking out sustainable seafood.

A few weeks ago, you offered some advice for your carnivorous readers on how to satisfy their meat cravings in a more eco-friendly fashion. But what about us pescetarians—got any tips for fish-lovers?

Salmon with caviar.
Salmon with caviar

The Lantern's advice for eating livestock came down to some pretty simple recommendations: Eat less of it, but when you do, choose poultry first, then pork, then beef or lamb.

Unfortunately, there's no easy hierarchy when it comes to fish. Part of this is due to the fact that the ocean offers such a diverse menu. The meat department at the Lantern's local Safeway, for example, carries just five varieties of terrestrial animals—beef, chicken, turkey, pork, and lamb. The much smaller seafood case, on the other hand, brims with dozens of options, from trout to halibut to shrimp to scallops. Given this abundance of edible marine life, it's difficult to come up with many simple rules for responsible consumption.

The most straightforward thing you can do is avoid eating any species that has been consistently overfished.  According to a recent report from the U.N.'s Food and Agriculture Organization, 28 percent of global fish stocks were overexploited, depleted, or recovering from depletion in 2007. Another 52 percent were fully exploited, meaning that catch levels had either reached or were close to reaching their maximum sustainable limits. (For more on the world's overfishing problems, watch the current documentary The End of the Line—billed as AnInconvenient Truth about the seafood industry.)

To find out how your favorite fish is doing, check out the Monterey Bay Aquarium's popular Seafood Watch program, which rates both wild-caught and farm-raised seafood as "best choice," "good alternative," or "avoid." For wild-caught fish, the program looks at stock levels but also takes fishing techniques into account—since some types of gear result in greater damage to the marine environment or higher levels of collateral damage to nontarget species. For farmed fish, which are often raised in net-pens in the open ocean, Seafood Watch looks at the potential for pollution and disease transference to the surrounding ecosystem. (Wild-caught Alaskan salmon, canned albacore tuna, and farmed rainbow trout all get high marks under this program.) In the supermarket, look for the Marine Stewardship Council's eco-label—a blue oval with a fish and a checkmark—which certifies that products come from sustainable fisheries.

One thing that Seafood Watch and the Marine Stewardship Council won't tell you, though, is the carbon footprint associated with your crab, tilapia, or halibut steak. How a farmed fish is fed and how a wild fish is caught are generally the most important factors when it comes to greenhouse gas emissions, and choosing one option over another can make a big difference.

Take salmon, for example—the third most popular seafood in America. According to unpublished research presented at the annual meeting of the American Association for the Advancement of Science, Scottish farm-raised salmon—whose diet include relatively high amounts of fish meal—incur about 3.3 pounds of carbon dioxide equivalent per pound of harvested fish, mostly because of the carbon intensity of their carnivorous diet.Norwegian salmon, on the other hand, eat a higher ratio ofplants, and thus their related emissions clock in at just 1.8 pounds. (For comparison, it takes 1.4 pounds of CO2 equivalent to produce a pound of chicken in the United States.)

On the wild-caught front, the same team of international researchers found that trolling for salmon results in 1.9 pounds of carbon dioxide equivalent per pound of fish, as compared with 0.4 pounds for gillnetting and a downright dainty 0.2 pounds for purse-seining.

At the moment, though, this kind of information remains largely invisible to consumers. Though most fishmongers will be able to tell you what part of the world your seafood comes from and whether it's wild or farmed, they probably won't know what the fish ate or what kind of gear was used to catch it.

For an easy way to cut your seafood-related emissions, try to shift your diet toward farmed oysters, mussels, and clams—these shellfish don't require any processed feed. (They eat plankton instead.) Many experts also recommend that you make like a European and learn to love smaller, schooling fish like sardines, anchovies, and mackerel. They're easier to catch than big, bottom-dwelling carnivores like cod and haddock, meaning less fuel is expended to harvest them. (Plus, since they're lower on the food chain, they're naturally more energy efficient.) Generally speaking, fish with abundant populations are easier to harvest, meaning that choosing fish from well-managed stocks is likely to cut your emissions, as well.

Finally, avoid fish that have been flown in from far away. When it comes to seafood, transportation generally accounts for fewer emissions than feed production or fuel use by fishing boats. But fresh seafood that's been airlifted from abroad will take an added toll on the planet.

Is there an environmental quandary that's been keeping you up at night? Send it to ask.the.lantern@gmail.com, and check this space every Tuesday.

Nina Shen Rastogi is a writer and editor, and is also the vice president for content at Figment.

  Slate Plus
Slate Picks
Dec. 19 2014 4:15 PM What Happened at Slate This Week? Staff writer Lily Hay Newman shares what stories intrigued her at the magazine this week.