It's sardine season! If you want fish that's healthy to eat and produced in a sustainable, well-managed way, follow Plenty's simple rule:  Pick small fry. That means small species, mind, not juvenile tuna, sea bass or swordfish who haven't had a chance to reproduce and are overfished, to boot. We're talking sardines, anchovies, and herring, who eat lower on the food chain, are packed with heart-healthy omega-3 oils and lowest in the mercury and other pollutants that collect in the fats of big old predators. Sardines are at their fattest and sweetest from now through early fall, and rated a "Best Choice" by the Monterey Bay Aquarium's Seafood Watch program, which has newly updated its recommendations this month.

How to cook the small fry? Fresh sardines are now on sale at fish markets. For how to prepare and cook, see this simple oven-broiled sardine recipe by sustainable chef Rick Moonen, coauthor of cookbook Fish Without a Doubt. We also love them simply grilled outdoors or quick-fried in a cast-iron pan, as recommended by Monterey seafood chef John Pisto (see our greener grilling tips for equipment and charcoal choices).

Big news this year:  Wild salmon from Alaska is now our only sustainable and healthy salmon choice. Wild salmon fisheries in California and Oregon have been closed due to population collapse, and Environmental Defense cautions against eating wild salmon from Washington State due to elevated levels of PCBs, which have caused learning problems in children of women who ate a diet high in polluted fish while pregnant.

Mercury, like PCBs, is a dangerous neurotoxin that crosses the umbilical cord, so fish with high and moderate mercury levels should be avoided by pregnant and nursing women, and to be safest, they and children younger than twelve shouldn't eat more than 6 ounces of white/albacore tuna a week, according to the Environmental Working Group (EWG). In cans, chunk light tuna is lower in mercury than white. or albacore. For how much you or your child can safely eat, according to your weight, see EWG's tuna calculator.

If you're travelling and want to eat fish and shellfish from local waters, especially from lakes and rivers and after storms, which can cause elevated pollutants from runoff, check safety advisories with local health departments or click on the EPA's handy map. Meanwhile, here's a quick crib sheet.

Top Fish Picks (low mercury and environmental impact):

Sardines

Wild Alaska Salmon

Farmed U.S. Rainbow Trout, Mussels, Clams, Oysters, Bay Scallops

Fish to Avoid (contains mercury, production harmful to environment):

Albacore, Bigeye, Yellowfin, and Bluefin Tuna

Chilean Seabass

Grouper

Monkfish

Orange Roughy

Atlantic Cod, Flounder, Halibut, Sole

For in-between, "Good Alternatives" fish and regional variations, download MBAQ's cards, or view them in a trice on your mobile device. 

Here's wishing you many delicious fish meals and net gains in omega-3s.

This story originally appeared in Plenty in July 2008. The story was added to MNN.com.

Copyright Environ Press 2008