Cooperative Fish and Wildlife Research Units Program: Iowa
Education, Research and Technical Assistance for Managing Our Natural Resources

Iowa Project

Factors Affecting Mercury Concentrations in Iowa Fishes

June 2014 - December 2016


Participating Agencies

  • Iowa Department of Natural Resources

Mercury is naturally present in the environment but levels have increased dramatically since the 19th century due to anthropogenic emissions. Mercury concentrations in fishes can be highly variable among species and populations driven by a range of biotic and abiotic factors. Larger and older fish typically have higher mercury concentrations compared to smaller and younger individuals. Understanding fish length-mercury concentration relationships is an important component of issuing fish consumption advisories because fish length is easy for anglers to measure and understand. However, large variation in mercury concentrations within a species and individuals of similar size is common. The majority of mercury in fish muscle is derived from dietary sources. Understanding trophic ecology and population dynamics (e.g., age, growth, mortality) are important aspects of understanding mercury concentrations in fishes. Goals and objectives are to: - Develop regression models to predict the concentration of mercury in a range of fishes as a function of fish total length across natural lakes, impoundments, reservoirs, and rivers to guide consumption advisories. - Evaluate regional (e.g., north vs south, east vs west) differences in mercury concentrations to help guide consumption advisories. Include additional biotic (e.g., age, food web dynamics) and abiotic (e.g. land use, water quality) factors in models to explain additional variation in mercury concentration not explained by fish length. - Evaluate temporal changes in mercury concentrations in largemouth bass to guide mercury sampling protocols.