I thought I’d bring this up as several people have mentioned it to me in both the comments and E-mail.
Aside from the Environmental Defence‘s list of proper seafood choices, there’s another list out there that one should be aware.
Monterey Bay Aquarium‘s Seafood Watch holds an annual conference to determine seafood choices, and compiles the list into 3 categories: Best Choices, Good Alternatives and Avoid. Please check out the list on the link prior, or download a card for you to carry (.pdf format).
As others have mentioned, it’s a bit more nuanced than the Environmental Defence’s, and both lists do not contradict one another. Between the two of them, there’s no reason why you shouldn’t be making informed seafood choices.