EarthTalk is a weekly installment from E/The Environmental Magazine.

Dear EarthTalk: How can I find out which seafood to avoid if I am concerned about lessening my impact on the environment and avoiding consuming unhealthy pollutants?

Several decades ago a fish-centric diet was considered to be not only healthy but also environmentally friendly. But today those of us who eat a lot of fish may not be doing ourselves or the environment any favor. The two major concerns are overfishing and pollution.

Demand for low-calorie, protein-rich fish has grown tremendously alongside increases in world population. At the same time, the technologies employed for catching seafood have improved to the point that the commercial fishing industry has essentially stripped the ocean of its once teeming fish populations. One recent analysis concluded that only 10 percent of the large predatory fish that once roamed the world’s oceans are left, due to overzealous sport and commercial fishing. Another study concluded that three-quarters of the world’s fisheries are either fully fished or overfished.

Pollution from industrial, agricultural and other everyday activities like electricity generation and automobile driving has also taken a serious toll on the health of the remaining fish species. Scientists routinely find unsafe levels of mercury, PCBs, dioxins, pesticides and other harsh toxins in the fat, internal organs and even muscle tissue of many different kinds of fish. These contaminants are then passed on up the food chain to our dinner plates.

According to Seafood Watch, a project of the Monterey Bay Aquarium that works to educate the public about the seafood crisis, consumers can make a difference by getting educated so as to make smart choices about what seafood to avoid. Consumers can download and print out free Seafood Watch pocket guides to the “best choices” across six different regions of the U.S.—after all, what’s abundant and sustainably harvested in your area may not be the same for someone across the country.

Another convenient way to get the low-down on the fish you may be contemplating buying at the grocer or a restaurant is to text “30644” with the message “FISH,” followed by the name of the specific fish in question. In a few seconds, an automated response will come back from the non-profit Blue Ocean Network’s FishPhone service with information on the status of the fish in question—and alternatives, should Blue Ocean consider the fish an undesirable choice.

The basic skinny on fish consumption is that if you like it, you should eat it, but responsibly—that means in moderation and armed with the proper knowledge of which types of fish to buy and which to avoid.

For those looking to cut down on or eliminate seafood from their diets but still gain the health benefits of eating fish, plenty of alternatives exist. As most vegetarians know, beans, tofu and many nuts can be significant alternative sources of protein. And walnuts, flaxseed and hemp oil/seeds are all rich in the Omega-3 fatty acids common in many fish and thought to help ward off heart disease, cancer, macular degeneration (age-related blindness), arthritis and inflammatory disorders.

CONTACTS: Seafood Watch, www.mbayaq.org/cr/seafoodwatch.asp; FishPhone, www.fishphone.org.

GOT AN ENVIRONMENTAL QUESTION? Send it to: EarthTalk, c/o E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881 USA; submit it at EarthTalk; or e-mail us. Read past columns at our archives.