USGS Shenandoah Smallmouth Bass Research Beginning to Find Answers

Shenandoah smallmouth bass with black spot.

Shenandoah smallmouth bass with black spot.

Shenandoah Riverkeeper began working with Dr. Vicki Blazer, of the USGS National Fish Health Research Laboratory in Kearneysville, WV, during the 2005 Fish Kill Task Force. Since then, we've assisted in the lab’s collection efforts and have been the eyes and ears for happenings on the river. The result of this collaboration is a greater understanding of the threats facing our smallmouth bass population. 

At the Chesapeake Bay Watershed Project’s November meeting, Blazer discussed fish health issues in the Chesapeake Watershed. Her research revealed three troubling issues: Shenandoah fish still suffer from skin lesions, an unnatural level of mortality of adult fish in the spring, and a high prevalence of intersex fish where mortalities are occurring. 

While no smoking gun was identified as the sole culprit for the 2005 Shenandoah fish kill (or the many others that followed), Blazer’s research sheds light on the role pesticides and other chemicals (e.g. neonicotinoids) play in the health of wild fish populations. It’s not good news.

She explained that many pesticides are produced to have a biological effect that, even at very low levels, can impact the endocrine and immune systems of fish. The USGS lab has determined that short-term exposure at sensitive life stages can have long-term or even permanent effects on fish. A high percentage of fish tested had multiple bacterial pathogens — often with heavy parasite infestations and some with opportunistic fungal infections. The pesticides also seem to be the cause of the high prevalence of intersex fish. Strong correlations were found between the presence of diseased fish with the percentage of agricultural land use, confined animal feeding operations and agricultural herbicides and pesticides.

In addition, Blazer and her team did not find a relationship with disease or indicators of estrogenic exposure with wastewater treatment effluent, which is where you would expect to find it, if the primary cause was estrogen residue resulting from birth control pills. 

Many questions remain unanswered so its important that Blazer and her team at USGS are able to continue their research. We are fortunate to have Dr. Blazer leading the way to learn more about the threats to our rivers. We look forward to contributing to this effort in the coming years.

A sample of Dr. Vicki Blazer’s research:

Kolpin, D.W., Blazer, V.S. , Gray, J.L., Focazio, M.J., Young, J.A ., Alvarez, D.A., Iwanowicz, L.R., Foreman, W.T., Furlong, E.T., Speiran, G.K., Zaugg, S.D., Hubbard, L.E., Meyer, M.T., Sandstrom, M.W. & Barber, L.B. (2013). Chemical Contaminants in Water and Sediment near fish nesting sites in the Potomac River Basin: Determining Potential Exposures to Smallmouth Bass (Micropterus dolomieu). Science of the Total Environment. 443C:700-716.

Stavreva, D.A., Klausmeyer, P., George, A.A., Varticovski, L., Sack, D., Voss, T.C., Schiltz, R.L., Blazer, V.S., Iwanowicz, L.R. & Hager, G. (2012). Prevalent Glucocorticoid and Androgen Activity in US Water Sources. Scientific Reports. 2:937.

Blazer, V.S., Iwanowicz, L.R., Henderson, H., Mazik, P.M., Jenkins, J.A., Alvarez, D.A., Young, J. (2011). Reproductive endocrine disruption in smallmouth bass (Micropterus dolomieu) in the Potomac River basin: Spatial and temporal comparisons of biological effects. Environmental Monitoring and Assessment, Published Online Aug 4, 2011.