We love fish and seafood and eat it about 6-8 times per week (based on 21 meals), so that probably qualifies us as high consumers (not at the level of the Japanese, of course, but pretty high for North Americans!). At those levels of consumption, the risk of contamination from mercury, bacteria, and other poisons, not to mention the environmental impact of consuming over-fished species, starts to become significant. The Monterey Bay Aquarium is a world-leading research and tracking institution for the health and sustainability of various edible species. It publishes Seafood Watch, a twice-yearly updated guide to recommended and not recommended species. Also available as a free iPhone app. The pdf version of the guide prints out as a handy wallet-sized guide that you can keep with you when you shop. Since I hate paper, the iPhone version is my preferred vehicle. Excellent web site, too.