Lake Erie is a popular fishing spot due to the abundance of sport fishes that can be found in its nutrient rich waters. Many fishermen and women flock to the shallowest of the Great Lakes every summer to see how many fish they can bring home for a tasty dinner. Did you know that each year the Ohio EPA compiles a list of fishes in Ohio that they have observed to contain dangerous levels of pollutants like polychlorinated biphenyls (PCBs) and mercury (OEPA, 2017)? These contaminants often enter waterways near disposal sites or near factories which use them for production. Once PCBs and mercury enter a stream, river or lake, they bind with the sediment or disperse throughout the water column, where they are easily available for uptake by fish. At this point, fish absorb or ingest the contaminants and because they do not easily dissolve, they are stored in the fish’s fatty tissues. When predators like other fish (or people!) eat the affected fish, the fatty tissues within the predator absorbs the PCBs or mercury (James and Kleinow, 2014). Watch the video below for a fun visual representation of this concept. The brown shading represents the contaminants within the fish and you’ll notice that as each fish gets eaten, the consumer adds to the stores in their own fatty tissues.
Above video made by Krystal Pocock using iMovie for iPhone 7.
PCBs and mercury accumulate in fatty tissues and have a negative impact on human health (Hanrahan et al., 1997; Watras et al., 1995). To prevent adverse health effects, the Ohio EPA makes recommendations as to the frequency and number of fish that are safe for consumption based on the average level of pollutant (e.g. mercury or PCBs) that a particular fish species has been found to contain. In 2017, the biggest listed offender in Lake Erie was the common carp. The OEPA recommends that individuals should only consume one common carp (over 27″) every two months. For a list of other recommendations for common sport fishes (including Small Mouth Bass), please check out the 2017 Ohio EPA Fish Advisory Pamphlet. If you decide to consume any of the fish included on this list, the OEPA also recommends that you trim as much of the fat off of the fish as you can to potentially decrease the amount of the contaminants you’ll be consuming (OEPA 2017). See the drawing below for an idea of where to trim the fat!
References:
Hanrahan, L. P., Falk, C., Anderson, H. A., Draheim, L., Kanarek, M. S., & Olson, J. (1999). Serum PCB and DDE Levels of Frequent Great Lakes Sport Fish Consumers—A First Look. Environmental Research, 80(2), S26–S37. https://doi.org/10.1006/enrs.1998.3914
James, M. O., & Kleinow, K. M. (2014). Seasonal influences on PCB retention and biotransformation in fish. Environmental Science and Pollution Research, 21(10), 6324–6333. https://doi.org/10.1007/s11356-013-1611-3
OEPA. (2017). Ohio Sport Fish Consumption Advisory. Retrieved from http://www.epa.state.oh.us/portals/35/fishadvisory/fishadvisory_pamphlet.pdf
Watras, C. J., Morrison, K. A., Host, J. S., & Bloom, N. S. (1995). Concentration of mercury species in relationship to other site-specific factors in the surface waters of northern Wisconsin lakes. Limnology and Oceanography, 40(3), 556–565. https://doi.org/10.4319/lo.1995.40.3.0556