According to the Environmental Protection Agency and Food and Drug Administration, fish represent an excellent source of low-calorie protein. However, eating fish with high mercury concentrations can be a potential health risk.
To protect the health of Colorado's anglers and maintain the quality of angling opportunities, the Lake and Reservoir Research group investigates methods to reduce mercury concentrations in fish.
For example, researchers conducted a study to determine if manipulating predatory sport fish growth would decrease mercury concentrations. For this particular project, researchers monitored a northern pike (top predator) population in College Lake, a 25-hectare reservoir located on the Colorado State University Foothills Research Campus in Fort Collins, Colo. Researchers took tissue biopsies from northern pike before and two months after College Lake was stocked with rainbow trout, a high energy, low-mercury concentration prey species. The result was a decrease in northern pike mercury concentrations equivalent to their weight gain (with some fish gaining over 35 percent of their own body weight in two months with a corresponding reduction in mercury concentration of approximately 35 percent).
Results from the study showed that stocking high quality, low-mercury prey is a rapid and effective method to reduce sport fish concentrations. However, researchers found that this method is only temporarily effective; once the stocked prey fish are all eaten, predatory fish growth slows and mercury concentrations return to their former levels. Continuously stocking prey fish can be expensive, especially in large lakes and reservoirs. Thus, results from this study revealed that managing for naturally occurring and reproducing populations of prey fish with high energy and low-mercury concentrations would be more economically and ecologically beneficial.
The Lake and Reservoir Research group will continue to characterize and potentially minimize health risks posed by mercury to anglers, their families and wildlife that consume sport fish and other fish.
Lepak, J.M., Hooten, M.B., and Johnson, B.M. 2012. The influence of external subsidies on diet, growth and Hg concentrations of freshwater sport fish: implications for fisheries management and the development of fish consumption advisories. Ecotoxicology. 21(7):1878-1888.
Stacy, W.L., and Lepak, J.M. 2012. Relative influence of prey mercury concentration, prey energy density and predator sex on sport fish mercury concentrations. Science of the Total Environment. 437:104-109.
Lepak, J.M., Kinzli, K.D., Fetherman, E.R., Pate, W.M., Hansen, A.G., Gardunio, E.I., Cathcart, C.N., Stacy, W.L., Underwood, Z.E., Brandt, M.M., Myrick, C.M., and Johnson, B.M. 2012. Manipulation of growth to reduce sport fish mercury concentrations on a whole-lake scale. Canadian Journal of Fisheries and Aquatic Sciences. 69(1):122-135.