Easy Answer: According to the Monterey Bay Aquarium's "Super Green List" the best fish for eating are: Albacore Tuna (troll- or pole-caught, from the U.S. or British Columbia), Freshwater Coho Salmon (farmed in tank systems, from the U.S.), Mussels (farmed), Oysters (farmed), Pacific Sardines (wild-caught), Rainbow Trout (farmed), Salmon (wild-caught, from Alaska)
The Gulf oil spill has turned seafood into a hot topic. Over at Ask Umbra, they're discussing Sylvia Earle's book: The World Is Blue: How Our Fate and the Ocean's Are One? with the provocative question "Isn't the ocean an all-you-can-eat buffet?"
The answer: It's not.
The Monterey Bay Aquarium releases national and regional seafood lists--with fish categorized as "Best Choices," "Good Alternatives," and "Avoid". (They also have a nifty, and free,iphone ap to help guide seafood choices.)
You can also look up other fish. The trick--knowing where your fish is from and how it was caught. Here are a few dinner time favs:
Seafood Watch ranks wild-caught salmon from Alaska or Washington as your best choices. Keep away from wild salmon from California and Oregon.
It all depends on the type of tuna (Albacore, Bigeye, Bluefin, Skipjack, Tongol, Yellowfin), where it's from and how it's caught. The full chart is available here. The Monterey Aquarium recommends looking for the Marine Stewardship Council logo on the can.
Your best choice is Pacific or Alaskan halibut that's been wild-caught.
US farmed tilapia is best. Steer clear of farmed tilapia from China. Why? There are pollution and management issues.
The most sustainable shrimp are farmed using tanks or ponds. Avoid imported farmed prawn.