By Brierley Wright, M.S., R.D. , February 22, 2012 - 1:02pm
You probably already know that you’re supposed to be eating fish twice a week. Fish are a lean, healthy source of protein—and the oily kinds, such as salmon, tuna, sardines, etc.—deliver those heart- and brain-healthy omega-3 fats you’ve probably also heard you should be getting in your diet. (Find out if you need an omega-3 supplement here. )
But then there’s also this concern about sustainability—and choosing seafood that’s sustainable.
So, if you’re like me, you often stand at the fish counter a little perplexed: what’s good for me and the planet?
Fortunately, Seafood Watch, the program run by the Monterey Bay Aquarium, has combined data from leading health organizations and environmental groups to come up with their list “Super Green: Best of the Best” of seafood that’s good for you and good for the environment.
To make the list, last updated in January 2010, fish must: a) have low levels of contaminants—below 216 parts per billion [ppb] mercury and 11 ppb PCBs; b) be high in health-promoting omega-3 fats; and c) come from a sustainable fishery.
Related: 7 Simple Ways to Avoid Chemicals & Toxins In Your Diet & Your Home 
Many other options are on the program’s list of “Best Choices” (seafoodwatch.org). The Blue Ocean Institute (blueocean.org) also has sustainability ratings and detailed information.
6 of the Healthiest Fish to Eat
Here are 6 fish—that are healthy for you and the planet—that Seafood Watch says you should be eating.
1. Albacore Tuna (troll- or pole-caught, from the U.S. or British Columbia)
Many tuna are high in mercury but albacore tuna—the kind of white tuna that’s commonly canned—gets a Super Green rating as long as (and this is the clincher) it is “troll- or pole-caught” in the U.S. or British Columbia. The reason: smaller (usually less than 20 pounds), younger fish are typically caught this way (as opposed to the larger fish caught on longlines). These fish have much lower mercury and contaminant ratings and those caught in colder northern waters often have higher omega-3 counts. The challenge: you need to do your homework to know how your fish was caught or look for the Marine Stewardship Council (MSC) blue eco label.
Related: 16 Easy, Healthy Tuna Recipes 
2. Salmon (wild-caught, Alaska)
To give you an idea of how well managed Alaska’s salmon fishery is, consider this: biologists are posted at river mouths to count how many wild fish return to spawn. If the numbers begin to dwindle, the fishery is closed before it reaches its limits, as was done recently with some Chinook fisheries. This close monitoring, along with strict quotas and careful management of water quality, means Alaska’s wild-caught salmon are both healthier (they pack 1,210 mg of omega-3s per 3-ounce serving and carry few contaminants) and more sustainable than just about any other salmon fishery.
Related: Easy Salmon Cakes & More Healthy Salmon Recipes 
3. Oysters (farmed)
Farmed oysters are good for you (a 3-ounce serving contains over 300 mg of omega-3s and about a third of the recommended daily values of iron). Better yet, they are actually good for the environment. Oysters feed off the natural nutrients and algae in the water, which improves water quality. They can also act as natural reefs, attracting and providing food for other fish. One health caveat: Raw shellfish, especially those from warm waters, may contain bacteria that can cause illnesses.
4. Sardines, Pacific (wild-caught)
The tiny, inexpensive sardine is making it onto many lists of superfoods and for good reason. It packs more omega-3s (1,950 mg!) per 3-ounce serving than salmon, tuna or just about any other food; it’s also one of the very, very few foods that’s naturally high in vitamin D. Many fish in the herring family are commonly called sardines. Quick to reproduce, Pacific sardines have rebounded from both overfishing and a natural collapse in the 1940s.
5. Rainbow Trout (farmed)
Though lake trout are high in contaminants, nearly all the trout you will find in the market is farmed rainbow trout. In the U.S., rainbow trout are farmed primarily in freshwater ponds and “raceways” where they are more protected from contaminants and fed a fishmeal diet that has been fine-tuned to conserve resources.
6. Freshwater Coho Salmon (farmed in tank systems, from the U.S.)
Freshwater coho salmon is the first—and only—farmed salmon to get a Super Green rating. All other farmed salmon still falls on Monterey Bay Aquarium’s Seafood Watch “avoid” list for a few reasons. Many farms use crowded pens where salmon are easily infected with parasites, may be treated with antibiotics and can spread disease to wild fish (one reason Alaska has banned salmon farms). Also, it can take as much as three pounds of wild fish to raise one pound of salmon. Coho, however, are raised in closed freshwater pens and require less feed, so the environmental impacts are reduced. They’re also a healthy source of omega-3s—one 3-ounce serving delivers 1,025 milligrams.
6 Fish to Avoid
A number of environmental organizations have also advocated taking many fish off the menu. The large fish listed below are just six examples EatingWell chose to highlight: popular fish that are both depleted and, in many cases, carry higher levels of mercury and PCBs. The Environmental Defense Fund (EDF) has also posted health advisories on some of these fish at edf.org.
1. Bluefin Tuna
In December 2009 the World Wildlife Fund put the bluefin tuna on its “10 for 2010” list of threatened species, alongside the giant panda, tigers and leatherback turtles. Though environmental groups are advocating for protected status, the bluefin continues to command as much as $177,000 a fish. Bluefin have high levels of mercury and their PCBs are so high that EDF recommends not eating this fish at all.
2. Chilean Sea Bass (aka Patagonian Toothfish)
Slow-growing and prized for its buttery meat, Chilean sea bass has been fished to near depletion in its native cold Antarctic waters. The methods used to catch them—trawlers and longlines—have also damaged the ocean floor and hooked albatross and other seabirds. At present, there is one well-managed fishery that is MSC-certified. EDF has issued a consumption advisory for Chilean sea bass due to high mercury levels: adults should eat no more than two meals per month and children aged 12 and younger should eat it no more than once a month.
High mercury levels in these giant fish have caused EDF to issue a consumption advisory. Groupers can live to be 40 but only reproduce over a short amount of time, making them vulnerable to overfishing.
This strange fish resembles a catfish in that it has whiskers and is a bottom dweller, but its light, fresh taste made it a staple for gourmets. The fish is recovering some after being depleted, but the trawlers that drag for it also threaten the habitat where it lives.
5. Orange Roughy
Like grouper, this fish lives a long life but is slow to reproduce, making it vulnerable to overfishing. As Seafood Watch puts it: “Orange roughy lives 100 years or more—so the fillet in your freezer might be from a fish older than your grandmother!” This also means it has high levels of mercury, causing EDF to issue a health advisory.
6. Salmon (farmed)
Most farmed salmon (and all salmon labeled “Atlantic salmon” is farmed) are raised in tightly packed, open-net pens often rife with parasites and diseases that threaten the wild salmon trying to swim by to their ancestral spawning waters. Farmed salmon are fed fishmeal, given antibiotics to combat diseases and have levels of PCBs high enough to rate a health advisory from EDF. Recently, however, freshwater-farmed Coho salmon have earned a Best Choice status from Seafood Watch. There is hope consumer pressure will encourage more farms to adopt better practices.
Related: Ditch These 4 Foods to Clean Up Your Diet 
Which fish on these lists do you eat or avoid? Tell us what you think below.