What’s happening to German eelpout?

From Hamburg, Germany, at a meeting of the Society of Environmental Toxicology and Chemistry–Europe

Along heavily polluted regions of Germany’s Baltic coast, populations of an eel-like fish have a high incidence of potentially serious reproductive anomalies, according to a new study. Some 10 to 25 percent of male eelpout (Zoarces viviparous) are intersex, which means they have characteristics of both genders. Some males had testes containing eggs, for example. Also, microscopic examination of gonads from pregnant females pulled from those regions shows that between 45 and 80 percent of them have degenerating eggs, a condition known as atresia.

Because both intersex and atresia result from inappropriate hormonal signals, these conditions may represent good markers of exposure to pollutants that mimic hormones, says Jens Gercken of the Institute of Applied Ecology in Neu Brodersdorf, Germany.

To test that idea, his team collected eelpout from fishermen who inadvertently landed the unwanted species.

As a gauge of pollution at five Baltic sites where fairly stable populations of eelpout reside, Gercken’s group measured the accumulation of toxic chemicals in mussels. The four westernmost sites–those with lots of port traffic, large sewage-plant outfalls, industrial activity, and drainage from upstream farms–were quite polluted. Among compounds found were DDT, tributyl tin, and polychlorinated biphenyls–all pollutants that can have a hormonal alter ego.

Gercken’s team reports that eelpout caught in the polluted waters exhibited higher rates of gonadal problems than fish from the one relatively clean coastal site. Gercken plans follow-up studies to home in on the specific chemicals triggering the eelpout’s problems.


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Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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