13 Best Fish: High in Omega-3s -- and Environment-Friendly

Purchase the best fish.

Buying fish can be a tricky task -- it's hard to find one that's healthy for both you and the ocean. There's no master guide ranking fish by what's important: high omega-3s, low mercury levels and healthy environmental factors. But here are 13 menu options that meet the bar on all those measures, according to the Environmental Defense Fund's Seafood Selector and the Monterey Bay Aquarium's Seafood Watch programs. These choices are high in omega-3s and low in contaminants, and they're produced in a way that's friendly to their environments. How you prepare a dish will obviously determine its calorie count, so unless noted, the calories listed here are for servings of uncooked fish.

1. Wild salmon from Alaska

Fresh, frozen or canned are all OK. Wild salmon will cost you a lot more (on average, $30 per pound) than the farmed variety, but it's worth the big bucks. Salmon farms hold up to 1 million fish per net, and this overcrowding exposes the farmed salmon to chemicals, lice, bacteria and viruses. Plus, salmon farming practices produce waste and can spread parasites and disease to wild fish, among other problems, according to Seafood Watch.

Calorie count: 180 per 4-ounce serving.

2. Arctic char

At a sushi bar, this fish is known as iwana. Arctic char is an environmentally friendly substitute for farmed salmon because it's farmed in systems that are chemical-free and usually void of diseases. It's fine to opt for this farmed fish over wild-caught (which isn't easy to get, anyway).

Calorie count: 204 per 4-ounce serving.

3. Atlantic mackerel

Mackerel populations in general are healthy, so wild-caught is A-OK. The EDF recommends you limit consumption of the Spanish and king species of mackerel because of their potential for mercury contamination, so stick to Atlantic mackerel as a staple.

Calorie count: 232 per 4-ounce serving.

4. Sardines

Sardine fishing on the west coast is closed because of a dramatic decline in the sardine population, so these tiny fish may be hard to locate in stores. If you're able to find them, they're a great snack because they don't come with the mercury worries of fish higher up the food chain, such as swordfish and grouper.

Calorie count: 232 per 4 ounces of drained, canned, oil-packed fish.

5. Sablefish/black cod

Sablefish is known for its rich, buttery flesh, which puts it in high demand. Seafood Watch recommends you stick to sablefish caught off California, Alaska and British Columbia, where fishing practices have reduced the likelihood of the accidental catch of other species. The EDF advises children 12 and under to eat only two servings a month due to a moderate mercury content.

Calorie count: 220 calories per 4-ounce serving.

6. Anchovies

This little fish is available year-round and can be frozen, raw or canned. Although all anchovies have low mercury levels and high omega-3s, Seafood Watch recommends only eating those fished from the Adriatic Sea, where fishing methods are sustainable and less likely to accidentally catch marine mammals.

Calorie count: 148 per 4-ounce serving.

7. Oysters

Oysters can be either farmed or caught in the wild (although wild-caught oysters are uncommon). Both methods are generally well-managed and have a low impact on the environment, so oysters are always a great option. At the sushi bar, you may see oysters called kaki.

Calorie count: 67 per 4-ounce serving.

8. Rainbow trout

Rainbow trout are farmed in different ways worldwide, and the safest methods are practiced in ponds, raceways and recirculating agricultural systems -- indoor farms that use a series of filters to keep fish clean. Seafood Watch says these farming techniques are effective and can control chemical pollution that was once problematic for this species.

Calorie count: 156 per 4-ounce serving.

9. Albacore tuna

Make sure it's caught from the North Atlantic Ocean or the Pacific Ocean, where fishermen use methods that don't accidentally snag other species. (Most canned tuna comes from fisheries that use more wasteful methods.) Kids 5 and under should limit consumption to two meals a month because of moderate mercury contamination, the EDF says.

Calorie count: 150 per 4-ounce serving of drained, canned, water-packed fish.

10. Mussels

Farmed mussels are raised in an environmentally responsible manner -- they're hung from ropes in the ocean. This causes minimal impact to the surrounding ecosystem and in some cases can actually improve the marine environment. You may see them called murugai at a sushi bar.

Calorie count: 97 per 4-ounce serving.

11. Pacific halibut

Overfishing has depleted the stock of Atlantic halibut, but the similar Pacific halibut remains an option. These fish are raised in marine fisheries and then caught with longlines, a fishing method more sustainable than nets (which are the main reason why Atlantic halibut are endangered). Still, the EDF suggests kids ages 5 and under eat Pacific halibut only twice a month because of its mild mercury content.

Calorie count: 142 per 4-ounce serving.

12. Rockfish

Exact species doesn't matter -- all types of rockfish caught in California are OK, according to the EDF. There are more than 70 species of rockfish living off the U.S. west coast, and most are healthy. A few stocks are recovering from overfishing, but a new management program installed by conservation groups is helping fishermen keep the marine ecosystem intact.

Calorie count: 106 per 4-ounce serving.

13. Catfish

Watch out for the country-of-origin label -- Seafood Watch recommends purchasing catfish raised exclusively in the U.S. because contamination can occur in countries such as Vietnam, Thailand and China, where the government doesn't regulate fish farming operations. Catfish is the most commonly farmed fish in the U.S. and is touted for its low mercury levels.

Calorie count: 108 per 4-ounce serving.