Bay’s intersex fish mystery remains unsolved

Ten years have gone by since one of the weirdest discoveries in the Chesapeake Bay region, on the south branch of the Potomac River — male smallmouth bass with lady parts, eggs in places where they absolutely should not be.

Over that decade, wildlife biologists have probed the bay’s tributaries, slicing open fish for more necropsies than anyone can count. And one thing is clear: They still aren’t sure why between 50 and 100 percent of bass in various locations are gender-bending, switching from male to something called intersex.

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Biologists say studies are falling short because of a lack of data on the type and quantity of pesticides that run into the bay from farms. This complaint, along with other factors, prompted Democrats in the Maryland House and Senate to sponsor two bills in the current legislative session that would for the first time require growers to record their use of insecticides and herbicides and submit it to the state.

The pesticide-reporting rule would create a treasure trove of data that scientists could draw from for studies on human and animal health, supporters say. Scientists could use it to focus research on chemical “hot spots,” the exact moment high concentrations of pesticides hit waters where vulnerable young fish are growing, said Vicki Blazer, a biologist who studies bass for the U.S. Geological Survey.

But opponents say the bills have major drawbacks. They would create a financial burden for farmers, who would be forced to purchase updated equipment such as Global Positioning System devices to log pesticide applications, said Valerie Connelly, director of government relations for the Maryland Farm Bureau.

Officials at the Maryland Department of Agriculture weighed in, saying it would need $1.5 million a year to form a new unit of employees to input data provided by farmers and maintain computers to process it.

“This is an expensive proposition, which is one of our big concerns with it,” said Carol Holko, assistant secretary for plant industries and pest management in the state’s Agriculture Department.

Maryland already requires farmers to record applications of restricted-use pesticides — powerful chemicals not available to the general public. But they don’t have to automatically report it to the state.

The proposals by Del. Stephen W. Lafferty (D-Baltimore County) in the House and Sen. Roger Manno (D-Montgomery County) that would require growers to report dozens of restricted pesticides at least once a year came on the heels of an Environmental Protection Agency report in December that said many fish in the bay are in bad health.

They struggle with “increased incidence of infectious disease and parasite infestations” that contribute to “increased mortality in several species,” the report said. It found feminization in both largemouth and smallmouth bass — eggs in the testes of males. There were also “tumors in bottom-dwelling fish,” a major concern for Maryland and District officials who caution anglers against eating carp and catfish.