Artificial Hormones Put Chesapeake Fish in a Spin

According to a U.S. Geological Survey (USGS) report, fish health and reproductive issues in the Chesapeake Bay drainage may be associated with fish exposure to hormone-mimicking compounds and other chemicals. USGS scientists have studied yellow perch, a species that has declined in recent years, and found that differences in the egg quality of these fish is occurring in some sites they sampled.

In addition, scientists sampled smallmouth bass and other species from major fish kills in the South Branch of the Potomac and the Shenandoah River. They found the fish were infected with a variety of types of skin lesions and a number of disease-causing bacteria, viruses and parasites. These findings suggest that the immune systems of these fish are weakened, reducing their resistance to disease.

Researchers also found high numbers of intersex bass collected in the same areas as the fish kills. Intersex fish, as well as the measurement of the female yolk protein, vitellogenin, in male fishes, have been most commonly associated with exposure to estrogen-mimicking compounds.

The co-occurrence of fish kills with these other reproductive effects suggests that endocrine-disrupting chemicals may affect not just individual fish, but also entire populations due to decreased disease resistance and reproductive effects. The distribution of bass with intersex and the possible association with land-use practices will be discussed.