Overfishing, harmful fishery techniques and habitat destruction have brought into question whether many of the world's fish stocks can sustain themselves. Does that mean we should stop eating fish if we care about the sea? "Definitely not," says Carole Baldwin, National Museum of Natural History marine biologist and coauthor of One Fish, Two Fish, Crawfish, Bluefish: The Smithsonian Sustainable Seafood Cookbook.

There are plenty of fisheries that use eco-friendly methods and limit their take with species' long-term survival in mind, Baldwin says. Although Chilean sea bass should be avoided in general because of overfishing, the Marine Stewardship Council (MSC) has certified a fishery off South Georgia Island near Antarctica as sustainable. Several other ventures aiming to produce environmentally sound farmed fish have recently launched. Australis Aquaculture in Massachusetts, for instance, raises Australian barramundi. "The operation emphasizes clean and healthy procedures—99 percent of the water is purified and recycled, there are no hormones, antibiotics or colorants and by using pure artesian well water they can assure that the fish is virtually free of mercury and other contaminants," says Baldwin.

With assistance from Baldwin, Smithsonian.com offers the following guide to ocean-friendly eating.
(Download a pocket-sized guide.)

BEST

Of all the seafood choices a consumer in North America can make, these are the most eco-friendly.

• U.S. farm-raised oysters, mussels and clams: Cultivated on both coasts in sound farming operations, these filter-feeders actually improve water quality.
• U.S. farm-raised barramundi, striped bass (rockfish), white sturgeon, catfish, tilapia and trout: These inland aquaculture operations cause minimal environmental harm.
• Sablefish: This tasty, eco-friendly alternative to Chilean sea bass is an example of a well-managed deep-sea fishery; it's certified as sustainable by the MSC.
• Ecofish brand canned albacore tuna (www.ecofish.com): It is sustainably caught using single fishing lines and is tested for contaminants, including mercury.
• Alaskan salmon: Wild Alaskan chum, coho, king, pink and sockeye salmon fisheries are all MSC-certified as well-managed and sustainable.
• Pollock (aka frozen fish sticks, imitation crabmeat): This MSC-certified operation is an excellent example of how an enormous fishery can be sustainably managed.
• Pacific halibut: Another example of a well-managed, West Coast fishery that's MSC certified.

GOOD

For the most part, fish from this group are safe to eat without harming the ocean.

• Mahi mahi/dolphin fish (U.S.): If available, choose fish caught with single, trolled fishing lines; mahi caught on longlines are sometimes associated with high rates of bycatch.
• Organic farmed salmon from British Columbia, Ireland and Scotland: Stocking density, feeding and growing methods make these fisheries more environmentally sound than typical farmed Atlantic salmon.
• Squid: These mollusks reproduce often, so they can withstand heavy fishing pressure—though many are caught in trawls with moderate bycatch rates.
• Anchovies, sardines, Atlantic herring and smelts: These species also reproduce enough to withstand heavy fishing.
• Pacific cod: All right to eat from MSC-certified fisheries in the Bering Sea and Aleutian Islands, Alaska.
• Atlantic and Spanish mackerel: These fast-growing fish are abundant.
• Farmed bay scallops: Most found in markets are farmed in safe systems in Asia.
• Atlantic sea scallops: If possible, choose diver scallops, which are hand-harvested rather than caught by dredges that can destroy ocean bottoms.
• American lobster: Cooperation among fishermen, scientists and authorities has helped maintain these populations, particularly through low-bycatch traps.
• Ocean shrimp (aka salad or cocktail shrimp), Northern pink shrimp, spot prawns: Not the typical shrimp found in seafood markets, these coldwater species are caught in special trawls or traps with minimal bycatch.
• U.S. Crawfish: Though U.S.-farmed crawfish, mostly in Louisiana, are an excellent choice, beware of Asian-farmed crawfish, which may be contaminated with potent antibiotics that are banned in U.S. operations.

OK, BUT

Eater beware.

• Alaskan snow and king crab: These populations are recovering under Alaskan fishery management plans.
• U.S. brown, pink and white shrimp: They are taken with trawl nets with turtle excluder and bycatch reduction devices; however, 90 percent of shrimp sold in the United States is imported from countries in Latin America and Southeast Asia, where environmental regulations are lax or nonexistent.
• Blue crabs: Avoid buying fresh crabs in the winter, when dredges may have been used to harvest females that have burrowed before spawning.
• Swordfish: They are recovering in the Atlantic, but most swordfish are caught with longlines, which have a large bycatch of juvenile billfish, sea turtles, seabirds and sharks, and they may contain high amounts of methylmercury.
• Yellowfin, skipjack and albacore tuna: Plentiful, but these fish are often caught with longlines.

BAD

Eating fish from this group will add to the problems facing the world's fish stocks.

• Atlantic salmon: Farming causes water pollution by introducing excess feed, waste products, antibiotics and the farmed fish themselves into the surrounding environment; farmed fish may interbreed with wild salmon to the detriment of the wild stock.
• Atlantic flounder, plaice, halibut and sole: All Atlantic flatfish species have been overfished, and the bottom-trawl methods used to catch them result in high rates of bycatch.
• Caribbean-imported spiny lobster: Some areas have poorly managed fisheries, and this species is overfished.
• Monkfish, Pacific rockfish, tilefish and king mackerel: These species are all either overfished, caught in bottom trawls, contain high mercury levels or several of the above.
• Foreign-farmed shrimp and crawfish: Some operations use chloramphenicol, for which the U.S. Food and Drug Administration states there is no known safe level of human exposure.
• Imported swordfish: In the absence of international regulations for reducing bycatch by longliners, many foreign fisheries are catching and killing large amounts of endangered sea turtles and birds.

WORST

For now, anyone concerned with the sustainability of the ocean should avoid eating these fish.

• Sharks: Populations are overfished throughout the world.
• Red snapper: These fish continue to be overfished, and juveniles are sometimes caught and killed as bycatch in the shrimp-trawl industry.
• Imported caviar from wild sturgeon: Some populations, such as Caspian Sea sturgeon, are close to extinction.
• Orange roughy: This very slow-growing species has been so overfished that it will likely take decades to return to healthy levels.
• Bluefin tuna: These fish are extremely depleted due to aggressive, illegal overfishing.
• Chilean sea bass (other than from an MSC-certified fishery): Unregulated overfishing and rampant poaching threaten this species from the cold, deep waters near Antarctica. Endangered albatrosses and other seabirds are often drowned when accidentally snagged by the longlines usually used in these fisheries.