Shrimp trawling may boost mercury in red snapper, stud...(c increase in mercury levels of fish in ...)

Date:11/26/2008

c increase in mercury levels of fish in areas that are trawled, but that's not surprising given the very small size of the fish we're sampling," says Chumchal. "Still, when you consider the ability of mercury to accumulate in ever-increasing levels as you move up the food chain, and the intense fishing effort throughout the northern shelf of the Gulf of Mexico, it's definitely an issue worth watching."

Mercury pollution in the ocean can be tied to human activities, such as coal burning and other industrial emissions. Mercury discharged into the air eventually returns to the earth's surface with rain or snow, either falling directly into the ocean or making its way there from land via groundwater, streams and rivers. Once deposited in ocean sediments, mercury is converted by sulfate-reducing bacteria into methyl mercury, a known nerve toxin that can accumulate in the tissues of marine animals as they consume smaller fish and microorganisms.

Methyl mercury is dangerous to everyone, but it can be especially harmful to the developing nervous systems of fetuses, young children and animals. For that reason, both the Environmental Protection Agency and the Food and Drug Administration have cautioned pregnant women to limit the consumption of certain types of fish due to concerns about mercury contamination.

"Most people don't eat enough fish with elevated mercury concentrations to put themselves at risk," Chumchal says. "It typically isn't a problem for adults."

As part of a larger LSU-led study investigating potential impacts of shrimp trawling on the continental shelf, Chumchal and colleagues studied mercury levels in juvenile red snapper less than 250 millimeters in total length, looking for connections between mercury contamination and factors such as fish size, habitat type and the prevalence of shrimp trawling in the area.

Specifically, they compared fish taken from heavily trawled sand, shell, and natural reef habita
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Contact: Matthew Chumchal m.m.chumchal@tcu.edu 817-257-6440 Dick Jones Communications Source:Eurekalert

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