BaselineMercury concentrations in the prey of apex piscivores from a large subtropical estuary

- We report Hg levels in prey of large piscivores from an estuary in the southeastern United States.
- Mean Hg levels ranged from 0.02 to 0.22 mg/kg in commonly consumed prey species.
- Elevated Hg in some individuals was associated with fish size and capture location.
- Geographic patterns in Hg levels differed among prey species.
- Resident prey species may be useful sentinels of Hg contamination in regional biota.

Estuaries are important ecosystems for mercury methylation and accumulation, yet few studies have quantified mercury levels in prey species that expose large estuarine piscivores to contamination. We measured mercury concentrations in key prey species from the Indian River Lagoon, Florida, USA, to characterize variability and assess the spatial distribution of mercury levels throughout the estuary. Mean mercury concentrations ranged from 0.015 mg/kg in Mugil cephalus to 0.222 mg/kg in Bairdiella chrysoura and varied considerably in some species. Spatial variation was observed within species, but a universal geographic pattern among species was not apparent, likely reflecting the broad habitat-use patterns associated with the estuarine-transient life histories of many of these common prey species. In contrast, estuarine-resident species, such as B. chrysoura, may be useful indicators of regional mercury methylation potential and bioaccumulation in biota. These results can advance future studies that relate dietary mercury uptake and mercury level variations in estuarine piscivores.