Environmental Services Program
Fish Tissue Monitoring
Some carcinogenic lipophilic chemicals and metals occur in small amounts in waters of the state and are bioconcentrated into fish and other aquatic fauna. While levels found in aquatic biota do not appear to represent problems to their survival or reproduction, the amounts found in fish tissue may represent a health concern for humans eating those fish. Information is needed on which fish species are the most susceptible, which chemicals are occurring and in what quantities, and how this varies by fish species, location within the state and over time.
This project requires fish collection from "trend” (fixed) stream sites and “status” (discretionary) stream or lake sites each year by the department's Water Quality Monitoring Section staff and the U.S. Environmental Protection Agency. Fixed sites are sampled once every two years, and the same sites are maintained for as long as possible. Fixed station data will be used primarily to assess ecological (food chain risk) and long term time trends. Bottom-feeders are the species of choice at all fixed sites. Recent fish tissue monitoring has focused more on discretionary sites and mercury levels in fish from those sites. Two samples are collected at most discretionary sites. One sample will be a bottom feeding species commonly consumed by humans and the other a non-bottom feeding species commonly consumed by humans. This data provides information used in consumption advisories as well as 305(b) and 303(d) purposes.
Fish are collected using an electrofishing boat, which passes a field of electricity through the water that causes a muscle response reaction from the fish forcing them towards the netsman. When the electric current is released the fish response is also released allowing the fish to retreat unharmed.
Samples are analyzed for metals, including mercury, cadmium, lead and selenium. Samples composed of bottom-feeding fish are also analyzed for organic compounds, including several pesticides and PCBs. Some samples of bottom-feeding fish from the long-term trend sites will be analyzed for dioxin.