Not so very long ago, the world’s oceans teemed with fish. But growing demand coupled with unsustainable fishing and fish farming methods has led to a drastic change—today, nearly 75% of the world’s fisheries are believed to be either fully fished or overfished.

As seafood consumers, we have the power to help. By asking for and purchasing seafood from sustainable sources, we can take pressure off endangered fisheries and feel better about the fish we’re eating, too.

Here’s how to make a difference: First, get one of the sustainable seafood pocket buying guides offered free by several organizations either online or by mail. Our favorite is the Monterey Bay Aquarium’s Seafood Watch program because it’s broken down into regional guides. Other good ones include the Blue Ocean Institute’s Guide to Ocean Friendly Seafood and Audubon’s Living Ocean Seafood Lover’s Guide.

Take the guide along when next you shop for fish, and ask lots of questions at the fish counter—the labeling at many markets is vague. Don’t take “I don’t know” for an answer, and be flexible. Say you’re planning to make theCod with Mushrooms, Garlic & Vermouth, but your market carries Atlantic cod (bad choice), not Pacific cod (better choice). The Atlantic codfish will thank you if you make something else for dinner—haddock and pollack are good cod substitutes.

While you’re there, request that the store adopt a sustainable seafood labeling program like the ones from theMarine Stewardship CouncilorFishWise. You can learn more about these programs at their Web sites; the FishWise site also has links to the seafood buying guides mentioned above.