Intersex Fish Linked To Population And Agriculture In Potomac River Wa

[Achilles Tang]

For several years, scientists have been working to determine why so many male smallmouth bass in the Potomac River basin have immature female egg cells in their testes - a form of intersex. They are closer to finding an answer. New research shows that a high incidence of intersex occurs in the Potomac watershed at sites where farming is most intense and where human population density is highest. The study also shows the greatest prevalence of this form of intersex, known as testicular oocytes, occurs in the spring, just before and during the spawning season. A prevalence of intersex is not unique to the Potomac basin, nor is it unique to smallmouth bass. It has been documented in other wild fish populations including spot-tail shiners in the St. Lawrence River, white suckers in Colorado, shovelnose sturgeon in the Mississippi, white perch from the Great Lakes, roach fish in the U.K and Denmark, sharp-tooth catfish in South Africa, three-spine stickleback in Germany, and barbel in Italy. It has also been noted in marine and estuarine fishes in Japan, the UK and the Mediterranean.

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