Sharks are commonly touted as playing a key role in food web dynamics as higher-order predators, leading to significant interest in shark research and conservation. Bonnethead sharks (Sphyrna tiburo) are a common mesopredators in coastal ecosystems spending a considerable amount of their life within estuaries. They appear seasonally in NC estuaries, and are potentially important predators on other key estuarine species such as blue crabs and red drum (based on work in Florida). Although the demography, social behaviors, and estuarine habitat use of this species has been studied in the Gulf of Mexico and along Florida, comparatively little work has been undertaken in NC. Complete understanding of the role these species serve in local ecosystems requires greater knowledge regarding the spatiotemporal patterns in movement and habitat utilization (together referred to as behaviors). We acoustically tracked the behaviors of bonnethead sharks in both North Carolina and Georgia estuaries to address three primary research questions: 1) What are the temporal patterns of bonnethead shark presence in NC and GA estuaries? 2) What are the spatial distribution patterns of tagged individuals within NC and GA estuaries? 3) Do individual sharks return to the same estuary in which they were tagged in consecutive years? During the summers of 2015, 2016 and 2017, a total of 20 bonnethead sharks in NC and 16 in GA were captured and tagged with Vemco acoustic transmitters. Overall, residency spanned March through November in GA estuaries and May through September in NC estuaries. Second, individual sharks generally expressed high degrees of site fidelity within NC and GA estuaries during seasonal residency with most sharks remaining near the location in which they were captured and tagged. Finally, there is evidence that bonnetheads show site fidelity across years with ~25% of individuals returning in both NC and GA between the first and second years of each study. Results from this study will contribute to our understanding of local food web dynamics in southeast US estuaries by elucidating potential spatiotemporal patterns of predation pressure on common prey items of bonnethead sharks.   

 

Funding Sources: NOAA Cooperative Institute for Coastal and Estuarine Environmental Technology

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Collaborators: *Martin Benavides, Joel Fodrie*, Matthew Kenworthy, Jeb Byers

     *Project PI