Intersex Fish Found in N.C. Waterways

By Elizabeth E. Payne

Researchers from North Carolina State University recently announced that more than half of the male black bass tested in rivers across North Carolina exhibited female characteristics, particularly the formation of egg cells in their testes.

Once published, their study will add to the evidence that intersex traits are appearing in fish nationwide. A 2009 U.S. Geological Survey study found that 91 percent of the largemouth bass sampled from the Yadkin-Pee Dee River in North Carolina exhibited such traits, the highest instance of any sample across the nation.

Scientists have linked these characteristics to the presence of endocrine disrupting compounds, particularly estrogens. In both humans and animals, the glands and hormones that make up the endocrine system regulate important functions such as growth, metabolism and reproduction. Endocrine disruptors interfere with naturally occurring hormones, potentially causing adverse effects.

According to a related study by NCSU researchers, these natural or synthetic compounds can often be traced to “municipal and agricultural waste flows” that enter waterways. Such compounds can include human contraceptives and growth hormones fed to animals, as well as pesticides that interrupt reproductive cycles.

“The results are worrisome,” Crystal S. Lee Pow, an NSCU doctoral student working on this study, told Environmental Health News. “Males are crucial for hatching success, and their male behavior could be altered by exposure to contaminants and the presence of the intersex condition.”