Chemical Combo and Intersex Fish Found at Smallmouth Bass Nesting Sites

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Chemical contaminants including herbicides, veterinary pharmaceuticals, and biogenic hormones have been detected at fish nesting sites in the Potomac River watershed where endocrine disruption in smallmouth bass (Micropterus dolomieu) was also observed. Although these contaminants are known to originate from a variety of human and animal-waste sources, results of a recent U.S. Geological Survey (USGS) study corroborate previous studies suggesting that seasonal runoff from agricultural activities is an important source of exposure to endocrine disrupting chemicals by smallmouth bass during critical life stages.

USGS scientist dissecting a fish to determine possible effects from exposure to endocrine disrupting contaminants

USGS scientist dissecting a fish to determine possible effects from exposure to endocrine disrupting contaminants.

(Credit: Vicki S. Blazer, USGS Leetown Center. Public domain.)

In the study, reported in Science of the Total Environment and Environmental Monitoring and Assessment, a team of USGSscientists collected water and bed sediment samples from fish nesting sites and studied fish from these sites where smallmouth bass spawn and build nests in the Potomac River watershed. This study and others help determine the seasonality and sources of chemical exposures contributing to abnormal fish health, such as intersex, observed in this region. Natural-resource managers, scientists, regulators, and others can use the results to inform decisions regarding overall fish health throughout the Chesapeake Bay region.

The Toxic Substances Hydrology, Contaminant Biology, Priority Ecosystems Science, and Fisheries: Aquatic and Endangered Resources Programs of the U.S. Geological Survey supported this study. Funding was also provided by the West Virginia Division of Natural Resources, West Virginia Department of Environmental Protection, Virginia Departments of Game and Inland Fisheries and Environmental Quality, and Maryland Department of Natural Resources.