Cruising the seafood counters at the Reading Terminal Market amounts to a grand tour of the ocean's bounty. I counted nearly 65 kinds of fish and shellfish in less than 10 minutes.

Catfish and clams. Scallops and shrimp. Yum.

But wait! Grouper is overfished. Chilean sea bass is caught with bottom longlines, which can entangle and kill sea birds. Orange roughy is overfished, and the bottom trawlers that catch it damage the sea floor.

Time to deploy my "Seafood Watch" wallet card, which categorizes species - by sustainability - as "best choices" (farmed tilapia and Pacific halibut, for instance), "good alternatives" (haddock and wild oysters), and "avoid" (monkfish and bluefin tuna).

The Monterey Bay Aquarium in California, which first issued the consumer cards in 1999, has since distributed 24 million nationwide. (See the clip-and-save newsprint version below.)

It even footnotes fish that may present other concerns, such as mercury contamination. But the point is sustainability - to steer us toward species that are "abundant, well-managed, and caught or farmed in environmentally friendly ways."

The National Marine Fisheries Service proudly notes that 80 percent of more than 250 federally managed fish populations are just fine. Most of what you see in a fish store is federally managed, if - and it's a big if - it's not imported or farmed.

But that also means 20 percent aren't.

And "if you look at fisheries globally," says Joshua Reichert, managing director of the Pew Environment Group, "they're generally in not good shape."

A warning on fisheries

Scientists have warned that commercial fisheries will collapse within 40 years if we don't change how they are managed. Not that the fish will be extinct, but they'll be so scarce you won't be able to catch them for a living.

Meanwhile, our hunger for seafood is robust. Americans eat upward of 16 pounds a year - a quarter of it shrimp. (A middling "good alternative," says Monterey Bay, as long as they're from the United States, either farmed or wild. All imported shrimp are on the "avoid" list.)

Some other groups even give recipes online. That certainly helps in the case of one of the Environmental Defense Fund's top choices: anchovies. (Try them in a garlicky Putanesca sauce.)

Blue Ocean's FishPhone service - a sustainability 911 - came in handy when I paused to admire pinkish fillets of something called "basa."

I pulled out my cell phone, dialed 30644 and texted "fish," then "basa."

A response came back in eight seconds: "imported, farmed, some environmental concerns . . . try U.S. farmed catfish instead."

FishPhone has fielded 18,000 queries since launching the service a year ago.

Environmental Defense, Blue Ocean and Monterey Bay will jointly publish a guide to sustainable sushi later this month.

Another view

Seafood purveyors are less than enthusiastic about all this. Scot Mackey of the Garden State Seafood Association harrumphed that there is "significant regulatory oversight" of fisheries, and he much prefers the New Jersey Department of Agriculture Web site that lists when various species are in season.