Fish fillet lead concentration sample locations in the Big River, Southeast Missouri Mining District Missouri, USA, 2005-2012

Lead (Pb) and calcium (Ca) concentrations were measured in fillet samples of longear sunfish (Lepomis megalotis) and suckers (Catostomidae) collected in 2005‒12 from the Big River, which drains a historical mining area in southeastern Missouri, where a consumption advisory is in effect due to elevated Pb concentrations in fish. Regression analysis indicated that fillet Ca explained 75‒>99% of fillet Pb variation in mining-affected stream reaches. We used analysis-of-covariance to standardize Pb concentration to a common Ca concentration (415 ug/g wet weight), which reduced differences between taxa. Variation among sites and years also was reduced after Ca-normalization, as was the number of samples that exceeded the 300 ng/g wet weight advisory threshold used in Missouri. Concentrations of Pb in 2005-12 were lower than they were in the past, especially after Ca-normalization, but the consumption advisory is still warranted. A simple linear regression model is proposed for estimating Ca-normalized Pb concentrations in fillets.