Science News Review

Intersex Fish and Water Pollution

Sep 15 at 5:05pm by Aileen

Back in February of 2008 the U.S. Geological Survey [USGS] conducted research on smallmouth bass in the Potomac River basin, finding that 80-100% of the fish collected from the Shenandoah were intersex. Meaning that males of the species had testicular oocytes [TO], or immature female egg cells in the testes.

The USGS researchers also documented that the highest prevalence of TO came attached to areas with the highest human populations and most intensive farming activity. This type of birth defect is connected to environmental exposures to endocrine disrupters (hormone precursors that affect the endocrine system), which are found in most agricultural pesticides, herbicides and fertilizers, and in many human/animal drugs. The prevalence of intersex had been at that time documented in other wild fish populations, including spot-tail shiners in the St. Lawrence, white suckers in Colorado, shovelnose sturgeon in the Mississippi, white perch in the Great Lakes, and in several species in the UK, Europe, Africa and Japan.

Intersex associated with endocrine disrupters in wastewater and farm runoff is nothing new, as reproductive anomalies in amphibians has been on the rise especially in farming regions for decades. Now the USGS has published new results of research on intersex in bass in the journal Aquatic Toxicology. They found that a third of all male smallmouth bass and a fifth of all male largemouth bass tested were intersex. The fish came from many different rivers and basins, including the Apalachicola, Colorado, Columbia, Rio Grande, Savannah, Pee Dee and Yukon. The Yukon is the only river basin where researchers found no intersex fish.

The Pee Dee river basin appears to have the biggest problem, though intersex bass are prevalent throughout the agricultural southeast. Relatively high incidence of intersex was also found in the lower Rio Grande basin, the Colorado and Gila in Arizona, and the Colorado basin. Lead author and USGS biologist Jo Ellen Hink suggested that “the widespread occurrence of intersex in fish would be a critical environmental concern.”

Well, duh. Any prognostications on when (or if) EPA and the USDA might get around to being critically concerned about it? Will “Intersex” become the new macho?