Sixty to 75 percent of male smallmouth bass in a tributary of Lake Champlain are "intersex," meaning they bear eggs.
The watershed for the Missisquoi River already has been a cause for concern because of runoff agricultural pollution that feeds blue-green algae blooms in the lake.
"The alarm to me is that these chemicals are present. They're in our water. They're in our food. We're exposing ourselves to them. To me, that's the alarm," said Vicki Blazer, a U.S. Geological Survey scientist and one of the report's authors.
She added that humans aren't exposed in the same way that fish are, since they aren't constantly in the water and our drinking water is treated. "But that doesn't mean we're not exposing ourselves to many of the same chemicals."
James Ehlers, executive director of Lake Champlain International, added, "I think they're basically Franken-fish. It's a canary in a coal mine, except it's bass in a river, and there's something monstrously out of balance in the natural system."
The herbicide atrazine could be a possible cause, as could the hormones contained in livestock wastes from factory farms.
"The big thing to me is that we don't truly understand the mix of things fish and other organisms are exposed to," Blazer said.
Intersex bass also have been found in the rivers and streams near and in wildlife refuges in the Northeast, as well as the Chesapeake Bay watershed.