Estimating Mercury Exposure of Piscivorous Birds and Sport Fish Using Prey Fish Monitoring

Area of Science:

• Environmental Science
• Ecotoxicology
• Wildlife Biology

Background:

• Methylmercury is a pervasive pollutant in aquatic ecosystems.
• Effective wildlife monitoring requires tools to predict mercury exposure.
• Piscivorous species are particularly vulnerable to methylmercury bioaccumulation.

Purpose of the Study:

• To develop predictive equations for methylmercury exposure in piscivorous birds and sport fish.
• To utilize mercury concentrations in prey fish as a key indicator.
• To provide tools for wildlife monitoring programs assessing mercury contamination.

Main Methods:

• Collected original data on grebes, sport fish, and prey fish from 25 California lakes.
• Measured mercury concentrations in blood and eggs of western and Clark's grebes.
• Analyzed mercury levels in various sport fish and 14 species of prey fish.

Main Results:

• Strong correlations were found between mercury in prey fish and mercury levels in grebes (blood and eggs) and sport fish.
• A 1.0 μg/g dw increase in prey fish mercury corresponded to significant increases in grebe blood (103%), eggs (92%), and sport fish (116%).
• High correlations were also observed between mercury concentrations in grebes and sport fish across lakes.

Conclusions:

• Prey fish mercury concentrations serve as a reliable predictor of mercury exposure in piscivorous birds and sport fish.
• This approach is valuable for estimating wildlife mercury exposure when direct sampling is not feasible.
• The developed equations can enhance the monitoring of methylmercury contamination in aquatic ecosystems.