Male bass in Potomac carrying eggs

Males of two different species of bass living in North America's Potomac River have been found to be carrying eggs, raising concerns that the river is dangerously polluted.

According to The Washington Post, some male Smallmouth bass and Largemouth bass, caught in the Potomac at Washington appear to be developing eggs inside their sex organs. While intersex fish were first recorded in the south branch of the Potomac in West Virginia in 2003, the latest findings show that the intersex fish are present over a much wider area of the Potomac drainage, including several tributaries.

Vicki Blazer, a fish pathologist with the US Geological Survey, told the Washington Post that more than 80% of the male smallmouth bass examined were growing eggs. At four of the seven sites surveyed every single male fish was affected.

Blazer believes that the Potomac watershed has a problem with endocrine disrupters - chemicals which are interfering with the natural endocrine system of the fish - which is causing males to turn on bodily processes normally only seen in females.

Blazer said: "What we're seeing now is that it's definitely not a problem just in the south branch. There is this sort of widespread endocrine disruption in the Potomac, but we still don't know what the causes are."

The reason for the abnormalities are not yet known, but scientists suspect that pollution in the Potomac may be to blame. Low levels of a number of endocrine disrupters have been detected, but none of them has been identified as the cause.

Thomas Jacobus, general manager of the Washington Aqueduct, which processes Potomac water for human consumption, told The Washington Post: "I don't know, and I don't think anybody knows, the answer to that question right now: Is the effect in the fish transferrable to humans?"