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Great Lakes Article:

Environmental Estrogens May Threaten Minnesota Walleye Fishery

11/08/2002


MINNEAPOLIS, MN - Some male fish that dwell in Minnesota waters are developing female characteristics, according to a study by Sea Grant researchers. Smaller sex organs, female proteins and sterility were some of the characteristics found among populations of walleye, fathead minnow and carp. The mix-up is caused when chemicals get into waterways and then interferes with the fishes' development and reproductive systems. The chemicals, known as environmental estrogens, act the same as natural estrogen, a female hormone. Trace amounts of the chemicals are enough to change the male fish. If too many fish lose their male traits, a drop in the fish population could lead to major ecological problems and impact the economically important recreational walleye fishing industry.

University of Minnesota Sea Grant researcher Deb Swackhamer and her team are studying two Minnesota waterways (Duluth-Superior Harbor and the Mississippi River near St. Paul) to learn more about the source of the environmental estrogens, as well as their effects on fish. Considered endocrine disruptors, the chemicals can reach the environment through sewage systems, paper mills, feed lots or industrial waste. Environmental estrogens can come from the natural hormone estrogen (found in animals, including humans), or from synthetic hormones like those found in birth control pills and industrial products such as detergents, packaging plastics and insecticides.

Many questions still remain. So far, researchers have been unable to pinpoint a specific chemical as the cause of the sexual changes. The team has found that some wild male walleye taken from waters near a sewage outflow of the Mississippi River had high levels of the female egg protein vitellogenin, decreased gonad size and no sperm. But laboratory goldfish exposed to the same water experienced much lesser effects. "Even these subtle effects may have an impact on wild fish," says Swackhamer, "where reproductive opportunities are limited and competition is severe." Further study of fish in Duluth, and eventually the entire Great Lakes, should give her team a better idea of what causes the fish to develop female characteristics.
CONTACT: Deb Swackhamer, Minnesota Sea Grant Researcher and University of Minnesota Professor, School of Public Health (O) 612-626-0435, Email: dswack@umn.edu


For more information, contact:
Ben Sherman

National Media Relations Director
National Sea Grant College Program
202-662-7095
sherman@nasw.org
Web site: http://www.seagrantnews.org
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