Potential Health Risks of Methylmercury Contamination to Largemouth Bass in the Southeastern United States

Widespread mercury (Hg) contamination of freshwater systems, due primarily to deposition of atmospheric inorganic Hg (IHg), poses a potential threat to recreational fisheries. In aquatic ecosystems, IHg is converted by bacteria to methylmercury (MeHg), a potent toxin that bioaccumulates in consumers and biomagnifies through the food web, reaching elevated concentrations in fish. Methylmercury has concentration‐dependent sublethal effects on fish, including reductions in reproductive output. In the present study, we conducted the first analysis of the potential health risks of MeHg contamination to largemouth bass (Micropterus salmoides), a popular game fish, in the southeastern United States. To assess the potential health risk posed by MeHg to largemouth bass, we compared MeHg concentrations in three sizes of adult largemouth bass to benchmarks associated with the onset of adverse health effects in fish. We also determined how the risk posed by MeHg to largemouth bass varied spatially throughout the southeastern United States. Our study suggests that in the southeastern United States MeHg poses a potential risk to largemouth bass health and that MeHg contamination may be detrimental to the fisheries of this economically important species of game fish. Environ Toxicol Chem 2023;42:1755–1762. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. In the southeastern United States, the potential health risks posed by methylmercury (MeHg) to largemouth bass increases with the average concentration of MeHg in largemouth bass within an ecoregion and largemouth bass size.