Daily News Archive
From December 19, 2000

Endocrine Disrupting Pesticides May Reverse Sex in Endangered Salmon

According to a study published in the January 2001 edition of Environmental Health Perspectives (Vol. 109, No. 1), 84% of wild fall chinook salmon (Oncorhynchus tshawytcha) phenotypic females that returned to spawn in the Columbia River had a genetic marker found only on the Y (male) chromosome.

As in humans, sex in salmon is determined chromosomally: females are XX and males are XY. The researchers, based out of the University of Idaho and Washington State University, tested for the presence of a genetic marker present only in XY individuals. Under normal circumstances, an individual with this genetic marker would grow up male, suggesting that 84% of the wild Chinook salmon were sex-reversed. None of the hatchery-raised salmon sampled demonstrated this abnormality.

The researchers believe the sex reversal is most likely due to the unnaturally high water temperatures induced by dams in the Columbia River basin and/or endocrine disrupting chemicals, including pesticides, polluting the Columbia River. The feminization of male fish by endrocrine disrupting chemicals was first discovered in England in the early 1990's. Subsequent studies have shown this phenomenon in the United States. Scientists believe that the feminization of male salmon and the resulting inability to reproduce is most likely contributing to the dwindling endangered salmon population in the Pacific Northwest.

To read the abstract visit http://ehpnet1.niehs.nih.gov/docs/2001/109p67-69nagler/abstract.html.