Chilean Sea Bass
Photograph by Paul A. Sutherland
How to Help
April 2007
Safe Seafood

Seafood lovers have a lot of concerns: Wild-caught or farm-raised fish? Sustainably harvested or whatever is fresh? High mercury levels? The good news is that for most adults—save for those pregnant or nursing—a recent Harvard School of Public Health study found that benefits of eating fish, particularly those rich with omega-3 fatty acids, outweigh risks from contaminants such as mercury often found in them. The bad news: We're eating fish nearly out of existence, and major stocks could collapse by mid-century if nations don't curtail the harvest. Advocacy groups offer seafood guides to help buyers make informed decisions about fish consumption. Though lists change from year to year and vary by region, a few species high in omega-3s and low in contaminants come from well-managed fisheries and tend to make the grade across the board.

Choose Safe, Sustainable Fish

  • Wild Alaska salmon
  • Canned pink or sockeye salmon
  • Anchovies
  • Sardines
  • Alaska sablefish (black cod)
  • Atlantic herring
  • Atlantic mackerel
  • Farmed oysters

Avoid High-mercury Fish

  • Tilefish (golden bass)
  • King mackerel
  • Shark
  • Swordfish
  • Freshwater sport fish caught in contaminated waters

Not All Fish Are Created Equal

While there are a few species to avoid, such as tilefish, shark, king mackerel, swordfish, and contaminated sport fish, eating seafood is generally good for you. Mercury poisoning, however, can be deadly, and mercury contamination can lead to a host of neurological problems.

A fish's mercury level depends on a number of factors, including where the fish lives, how old it is, how big it is, and what it eats. Mercury travels up the food chain, so fish that eat other fish are more likely to be contaminated. Mercury levels accumulate over time, so older fish are more likely to have larger concentrations of mercury than younger members of the same species. That means smaller aquatic species (shrimp, scallops, tilapia) are safer bets to guard against contamination. Anchovies and sardines, being small and short-lived, also have low mercury levels. Large, predatory fish (large tuna, sharks, swordfish) contain higher levels of mercury. In fact, fish at the top of the food chain can contain mercury levels that are 10,000 to 100,000 times higher than those of their environments. This helps explain why sharks are on the list of high-mercury foods and wild salmon are not.

While the Harvard study stressed that the benefits of eating fish outweigh the risks, note that—in addition to pregnant and nursing women—small children and women of childbearing age should also be careful to avoid contaminated fish.

Shopping for Seafood: What to Ask and Why

When shopping for seafood, be prepared to ask questions and look for information to help you figure out the best fish to buy. There are many factors to consider, and these questions will give you a place to start.

Where did the fish come from?
Knowing where in the world your fish came from will give you an idea of the strength of the regulations—if they exist at all—aimed to protect the consumer. You'll also be able to gauge whether sustainable fishing methods were likely to have been used and if the species is being overfished. Different fishing methods affect the marine environment and its marine animals differently. For instance, California's Monterey Bay Aquarium recommends avoiding farmed tilapia from Taiwan and China because of poor oversight and pollution concerns but recommends farmed tilapia from the United States.

Was the seafood raised on an aquatic farm or caught in the wild?
This question brings up a host of issues, including sustainable fishing and contamination. Farmed salmon, for instance, may have higher levels of dioxin and PCBs than its wild cousin. Studies have shown that farmed salmon can have some of the highest levels of PCBs of any fish in the world. Fats and oils in fishmeal consumed by farmed salmon are the problem; toxic PCBs concentrate in these substances.

What method was used to catch the fish?
If you can find out the answer, you'll gain an idea of the environmental effects of your choice. A Dungeness crab caught in a trap means there is little chance that other marine animals are caught and then discarded as bycatch. Atlantic haddock caught by trawling can destroy habitat and lead to other fish being discarded as bycatch. Haddock caught using hook-and-line methods is a better alternative.

Tuna: Know Your ABCs

Tuna has gotten a lot of press lately—both good and bad. Tuna is a good source of omega-3s, which are great for healthy cell membranes, but there are issues of moderate mercury contamination and sustainability of certain populations.

Ahi and albacore
Ahi is the Hawaiian word for tuna and can refer to yellowfin or bigeye tuna—both higher in mercury than canned, light tuna. Being called ahi doesn't necessarily tell you what tuna you are about to eat.

The Environmental Protection Agency (EPA) estimates that albacore, or solid white tuna, has three times the mercury on average of canned, light tuna.

Bigeye and bluefin
Both bigeye and bluefin tuna suffer from overfishing and low numbers, not to mention being higher in mercury than other kinds of tuna. Bigeye has the highest mercury level of all tuna listed on the EPA's website. Bluefin is not listed. Overall, it's best to avoid both.

Chunk light and chunk white
Read the can when you buy tuna: chunk white is not the same as chunk light. Chunk white comes from albacore tuna, which is on average higher in mercury than chunk light. Chunk light usually consists of skipjack. Since skipjack are smaller than other tuna and mature quickly, they have less body mass to accumulate mercury. However, a 2005 Chicago Tribune investigation found that some cans labeled "chunk light" also contained yellowfin tuna, which the EPA estimates averages one and a half times the amount of mercury as that of skipjack. Canned albacore tuna averages three times the amount of mercury as that found in other canned tuna, according to the EPA.

Seafood Seal of Approval

If you don't have room in your pocket for a seafood guide but still want to buy fish responsibly, look for the blue logo of the Marine Stewardship Council (MSC). This nonprofit based in the United Kingdom has developed a standard for sustainable fishing using principles put forth by the Food and Agriculture Organization of the United Nations. In order to receive permission to use the logo, a fishery must have sufficient numbers of fish and use methods that do not harm the surrounding marine environment.

Today, hundreds of seafood products from some 20 certified fisheries display the council's blue oval. Products with the logo are sold in supermarkets in 27 countries worldwide. In 2006 Wal-Mart, the world's number-one retailer, pledged that within three to five years it would buy all of its fresh and frozen seafood from MSC-approved fisheries. If you still can't find certified fish in your local market, the council urges you to pass along their contact information where you buy fish to spread the word about sustainable fisheries management.

For More Information

These organizations offer up-to-date lists of the wisest fish choices:

Monterey Bay Aquarium
Read up on detailed regional and national guides to seafood.

Environmental Defense
This website highlights fish species high in omega-3s—and also those high in contaminants.

Marine Stewardship Council
The council labels seafood from environmentally responsible fisheries.

National Audubon Society
The Society produces wallet-size fish guides for consumers to take along to restaurants.

U.S. Department of Health and Human Services and the Environmental Protection Agency (EPA)
Read this pamphlet produced by the EPA and the Federal Drug Administration to find out what you need to know about mercury in fish and shellfish, and how to eat seafood safely.

Natural Resources Defense Council (NRDC)
The NRDC offers a wallet-size card with information on the mercury content in fish as well as the amount of canned tuna you can safely eat depending on your weight.

Got Mercury?
This site provides a calculator—using data from the EPA—that breaks out mercury content per serving size and your weight.

Seafood Choices: Balancing Benefits and Risks
This report by the Institute of Medicine of the National Academies provides consumers with information on weighing the benefits and risks of different fish and shellfish and understanding the trade-offs of substituting seafood for other protein sources.

Conserve Our Ocean Legacy
This organization's site, sponsored by the National Environmental Trust, keeps you updated on issues affecting U.S. fisheries and their wildlife. You can also sign a petition urging the National Marine Fisheries Service to end overfishing and rebuild already depleted fish populations.