Abstract
The hard clam (Mercenaria spp.) historically supported a large fishery and aquaculture industry in Florida. In recent decades, overharvesting, pollution, red tide, and habitat loss have negatively impacted both wild and cultured Mercenaria spp. populations. Hard clam restoration efforts are underway, yet the factors limiting natural recovery—such as predation pressure—have not been well characterized. To fill this research gap, I quantified predators of hard clams by surveyed underwater transects monthly and deployed baited remote underwater video and tethered hard clams to assess types and prevalence of consumption on Mercenaria. Surveys were conducted from August 2024 – April 2025 at sites across four regions of Charlotte Harbor Estuary (CHE). As part of a larger study, I also surveyed the abundance of juvenile and adult hard clam, as well as other infaunal species, in these regions in August 2023, March 2024, and June 2024. These surveys were the first effort to determine what predators may be significant sources of clam mortality in CHE. Hard clam distributions across CHE were patchy, and overall densities were low, averaging < 1.0 m-2. Predatory gastropods and crustaceans were most abundant, averaging 3.3 and 6.0 m-2, respectively. Tethering experiments provided evidence of predation by gastropods and crabs, and their abundance in quadrat surveys and presence in baited video recordings suggest that these species are common predators of hard clams in CHE. While there were no significant correlations between clam and predator abundances, the relatively high abundance of predators and lack of juvenile and adult hard clams suggest the potential for top-down control. My study found both prey and predator densities were greatest in regions near the mouths of the Caloosahatchee, Peace, and Myakka rivers, suggesting that predators inhabit regions where prey items are abundant. While more research is needed, this study suggests that predator pressure may be a driver of hard clam abundance and distributions in the CHE. Management strategies and restoration efforts should consider measures to mitigate predation of both larger epibenthic species and smaller infaunal species that may target juvenile clams.