You can have your fish and eat it, too—if you choose fish that's caught or farmed sustainably. To figure that out, I use information provided by the Monterey Bay Aquarium. Go to www.mbayaq.org, click on seafood watch, and download a foldable card you can carry in your wallet.

The 'green light' list shows the most sustainable choices. These include Pacific halibut, Dungeness crab, farmed mussels, and wild-caught Alaskan salmon. The 'red lights' include Chilean sea bass, farmed Atlantic salmon, sharks, imported farmed or wild-caught shrimp, imported swordfish, red snapper, and imported bluefin tuna. Interestingly enough, many of these fish to avoid are also top predators whose bodies become loaded with mercury or other contaminants over time, so there's a double reason to avoid them—for your health and the environment.

Imported shrimp present serious problems that many people still don't know about. Although U.S. shrimp operations are better regulated and more sustainable, most shrimp sold today come from Asia or Central America.

With wild-caught shrimp, nets can snare 5 to 12 times as much bycatch (including turtles and such) as shrimp! Shrimp farmers generally bulldoze mangroves along the shoreline to create ponds—which soon become so polluted, they abandon them and dig new ones. So it leaves a trail of massive habitat destruction. We have already lost between a third and half of the world's mangroves, due to a combination of shrimp farming and coastal development.

We all can help spread awareness about the need to fix our oceans and reward businesses that have good practices. Pulling out your Seafood Watch card at a restaurant starts conversations with the waitperson and the chef. Even Wal-Mart has announced that within five years, it will sell only sustainably caught or farmed seafood. So this is going mainstream!

—Jane Lubchenco, PhD, professor of marine biology and zoology at Oregon State University