- The Washington Times - Thursday, June 4, 2009

Some of the same pollutants that apparently cause male fish in the Potomac and Shenandoah rivers to exhibit female characteristics may also leave them vulnerable to disease and large-scale fish kills, according to a new study.

The study points to a possible link between the occurrence of intersex fish and fish kills in the rivers in recent years.

In the study from the U.S. Geological Survey by researcher Laura Robertson, largemouth bass were injected with estrogen. Those fish were then found to produce lower levels of a hormone called hepcidin that is believed to bolster immune systems.

The study involved 24 fish, including control groups, that were monitored in the survey’s labs at Leetown, W.Va. It was published in the current edition of Fish and Shellfish Immunology.

Previous studies have shown that intersex fish were susceptible to lesions and other general illnesses, prompting Miss Robertson’s study.

Fish kills have plagued the Shenandoah and its tributaries since 2003. In 2005, up to 80 percent of the smallmouth bass and redbreast sunfish in the river’s South Fork died, and a similar kill occurred on the North Fork in 2004. Many of the dead fish exhibited intersex characteristics.

Intersex fish were first discovered in the Potomac in 2003.

A 2008 study found as many as 77 percent of male smallmouth bass in the South Branch of the Potomac had started to produce eggs, with the highest percentages adjacent to farming and population centers.

Many scientists suspect that pollutants, including certain household detergents, and drugs like birth-control pills that make their way into the water supply are the cause.

Legislation introduced in Congress would encourage state governments to establish programs to recover unused prescription drugs from consumers to prevent them from going into landfills or being flushed down the toilet.

“Alarm bells go off when 80 percent of male bass in the Potomac River are found to produce eggs,” said Rep. James P. Moran, Virginia Democrat and a co-sponsor of the legislation who is encouraging further study of the issue.

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