Maternal body burdens of methylmercury impair survival skills of offspring in Atlantic croaker (Micropogonias undulatus)

Methylmercury (MeHg), the organic form of mercury, bioaccumulates easily through the food chain. Fish in high trophic levels can accumulate substantial levels of MeHg and transfer it to their developing eggs. Here, the effects of maternally derived MeHg on the planktonic larval stage of Atlantic croaker were investigated. Adult Atlantic croaker were fed MeHg-contaminated food at three levels: 0, 0.05, and 0.1 mg kg⁻¹ day⁻¹ for 1 month. Fish were then induced to spawn and MeHg levels in the eggs were measured (0.04–4.6 ng g⁻¹). Behavioral performance of exposed and control larvae was measured at four developmental stages: end of yolk absorption (yolk), end of oil absorption (oil), and 4 and 11 days after oil absorption (oil + 4 and oil + 11). Behaviors analyzed included survival skills related to foraging and predator evasion: routine behavior (rate of travel, active swimming speed, net-to-gross displacement ratio, and activity) and startle response to a visual and a vibratory stimulus (responsiveness, reactive distance, response distance, response duration, average response speed, and maximum response speed). Maternally transferred MeHg induced concentration-dependent effects on survival skills. Statistical and simulation models applied to predict the ecological consequences of the behavioral effects suggested that maternal transfer of MeHg may substantially lower survival of planktonic stage larvae compared to unexposed larvae. These results also imply that larvae of top predatory fish species, such as blue marlin, may suffer mortality through maternal transfer of MeHg.