Catch of the day: Mercury? Check to see if the fish are safe to eat.

RODALE NEWS, EMMAUS, PA—It's no secret that much of our fish is laden with mercury, a neurotoxic heavy metal that is especially dangerous to children and developing fetuses. But a new report reveals it's not just the oceangoing tuna and swordfish that often harbor dangerous levels, but also freshwater species sought out by recreational fisherman. Every freshwater fish tested in a recently released United States Geological Survey (USGS) report contained some level of mercury, but more than a quarter of the tested fish were contaminated with mercury levels classified by the U.S. Environmental Protection Agency as unsafe to eat.

THE DETAILS: Researchers involved in the investigative report, titled "Mercury in Fish, Bed Sediment, and Water from Streams Across the United States, 1998–2005," focused their attention on testing predatory freshwater fish, including largemouth and smallmouth bass, along with brook, rainbow, and brown trout—in other words, game species fisherman are often after. The researchers sampled mercury contamination in these fish from different streams across the country, in urban, agricultural, and undeveloped areas, along with streams in areas that were historically mined for mercury or gold. Mercury contamination was so high in 27 percent of tested fish that it exceeded the EPA's safe level for human consumption. While fish with unsafe levels were found all over the country, the highest concentrations were found in fish taken from blackwater coastal-plain streams flowing from forests or wetlands in the eastern and southeastern U.S., along with streams draining gold- or mercury-mined basins in the western states. Although wetland areas are invaluable because they filter out many viruses, oils, and other pollution, bacteria in the ecosystem actually break mercury contaminants into its most toxic form.