posted on 2015-11-17, 00:00authored byJoshua T. Ackerman, C. Alex Hartman, Collin
A. Eagles-Smith, Mark P. Herzog, Jay Davis, Gary Ichikawa, Autumn Bonnema
Methylmercury is a global pollutant
of aquatic ecosystems, and
monitoring programs need tools to predict mercury exposure of wildlife.
We developed equations to estimate methylmercury exposure of piscivorous
birds and sport fish using mercury concentrations in prey fish. We
collected original data on western grebes (Aechmophorus occidentalis) and Clark’s grebes (Aechmophorus clarkii) and summarized the published literature to generate predictive
equations specific to grebes and a general equation for piscivorous
birds. We measured mercury concentrations in 354 grebes (blood averaged
1.06 ± 0.08 μg/g ww), 101 grebe eggs, 230 sport fish (predominantly
largemouth bass and rainbow trout), and 505 prey fish (14 species)
at 25 lakes throughout California. Mercury concentrations in grebe
blood, grebe eggs, and sport fish were strongly related to mercury
concentrations in prey fish among lakes. Each 1.0 μg/g dw (∼0.24
μg/g ww) increase in prey fish resulted in an increase in mercury
concentrations of 103% in grebe blood, 92% in grebe eggs, and 116%
in sport fish. We also found strong correlations between mercury concentrations
in grebes and sport fish among lakes. Our results indicate that prey
fish monitoring can be used to estimate mercury exposure of piscivorous
birds and sport fish when wildlife cannot be directly sampled.