BALTIMORE - 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.

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 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 of Columbia officials who caution anglers against eating carp and catfish.

The problem goes beyond fish, the report said. Birds of prey in a few locations experience eggshell thinning associated with certain chemicals.

The EPA found monitoring gaps where "some pesticides currently in use" couldn't be accounted for. A better accounting and more research into pesticide mixtures would help scientists understand the impact of chemicals on fish and wildlife.

But the farm lobby and officials in agriculture say the Maryland proposals also have gaps. The would not go after all the chemicals that concern the EPA, such as pesticides used to fight indoor pests and weeds sprouting in driveways and lawns.

They only target pesticides that can be used by certified professionals. Only 3,500 of Maryland's 13,000 farms are certified to use pesticides that would trigger the reporting, agriculture officials said. An additional 3,500 private companies and state agencies are also certified.

"I have 1,450 acres on 11 farms," Chip Councell, a Talbot County farmer, said in testimony last week at a Senate committee hearing. "To compile this into a format I'd have to put data loggers on five pieces of equipment at a cost of between $100,000 and $125,000. Every day I spend time at my desk is a day I am not taking care of my crops."

But other farmers, such as Holly Budd of Holly's Garden in Sunderland, Md., said reporting would benefit farmers by helping to identify harmful pesticides. Jenny Levin of Maryland PIRG, a consumer rights group, called the proposal "a right to know bill" that discloses the use of poisonous chemicals.

Three million people drink from the Potomac, where intersex fish have been found. Maryland would become the fourth state to adopt more stringent reporting rules if a law passes.

California has required its growers to report insecticide and herbicide use since 1990, producing so much data that the state struggles to process it. "This is used by government agencies, environmental groups, researchers, public health officials," said Larry Wilhoit, a research scientist for the state's Department of Pesticide Regulation.

New York started a program in 1996 but hasn't completed an annual usage report since 2005, amid disputes over the validity of the data, according to a report from the Maryland Agriculture Department. Oregon's program, started in 1999, was idled 1o years later when funding was stripped by budget cuts.

Maryland reporting is important because the state sits on the nation's largest estuary, a stunningly beautiful nursery for a wide variety of marine life, and a drinking source for millions of people in several states and the District.

But the bay's beauty is skin deep, said Blazer, the USGS biologist. It is beset by farms with huge pesticide loads and urban areas that send storm water overflows full of human waste and pharmaceutical products cascading into its tributaries.

Fish swim in a soup with ingredients that include low levels of pesticides with chemicals such as atrazine, mood-control pharmaceuticals and birth-control pills with powerful hormonal components that don't easily break down.

At a time when young bass are most vulnerable and sensitive to chemicals, the first couple of weeks of life in late May early June, farmers are preparing their land for planting by spreading manure with natural hormones that could cause intersex fish, Blazer said.

But all the talk about cross-gender fish misses the point, she said.

"Obviously I care about the environment, but the fish is an indicator that something else is really wrong," she said.

"But what are these things doing to the natural environment? If we find these things in wild organisms, there's a good chance they're also affecting people. People are spraying these pesticides and herbicides around their homes. All of those things we tend not to think about because of our lifestyle."