Scientists have discovered sexually altered fish off the Southern California coast, raising concerns that treated sewage discharged into the ocean contains chemicals that can affect an animal's reproductive system.
So-called intersex animals are not new, but most previous instances were in freshwater. Environmentalists say this is among the first studies to document the effects in a marine environment.
Last year, federal scientists reported finding egg-growing male fish in Maryland's Potomac River. They think the abnormality may be caused by pollutants from sewage plants, feedlots and factories.
In the latest studies, presented at Monday's Society of Environmental Toxicology and Chemistry conference in Baltimore, scientists caught 82 male English sole and hornyhead turbot off Los Angeles and Orange counties.
Of those, 11 possessed ovary tissue in their testes, said Doris Vidal of the Southern California Coastal Water Research Project, who led one of the studies.
Scientists do not yet know how such sexual defects affect the overall fish population.
Although the wastewater is filtered, it still contains contaminants that settle onto the ocean floor.
Two related studies found that two-thirds of male fish near the Orange County pipeline had egg-producing qualities. In a laboratory experiment, male fish exposed to sediment collected from the pipelines also developed egg-producing traits.
Steve Weisberg, who heads the water research project, said the results warrant further study to determine whether sexually altered fish are widespread in ocean waters.