The Monterey Bay Aquarium web pages are a tremendous resource. In particular, their Seafood Watch pages are a very complete guide to which fish are ok to eat and which to avoid. From that page you can search or browse through their data.

If you're headed to the fish market, there's even a pocket guide to Hawaii which is kept current on their web pages. Just print it out, cut, fold and take along for information at your fingertips. For more detailed information at home, go to their web pages.

Here is the seafood guide for Hawaii and here is the pocket guide.