Spatiotemporal patterns and habitat use of silky and sandbar sharks at Flower Garden Banks National Marine Sanctuary

Introduction Understanding the spatiotemporal movements of organisms within marine protected areas are essential for evaluating the efficacy of management practices designed to protect and conserve species. However, establishing management regulations to encompass species with large spatial extents can impose significant challenges when baseline data are limited. Flower Garden Banks National Marine Sanctuary (FGBNMS) in the northwestern Gulf of Mexico is a unique MPA for evaluating these concerns, as its remote offshore location provides natural benthic habitat for tropical fishes and foraging opportunities for many highly migratory species such as tunas, billfishes, and sharks. The silky shark ( Carcharhinus falciformis ) and sandbar shark ( Carcharhinus plumbeus ) are two elasmobranchs that frequent the sanctuary and surrounding habitats, yet their spatiotemporal movement patterns within this region remain poorly understood. Methods Movement patterns of 23 silky and 22 sandbar sharks were investigated using acoustic telemetry from August 2022 to October 2025. Acoustic receivers were deployed along the continental shelf at 17 banks within the sanctuary, four non-sanctuary banks, and 14 artificial reefs. Results Silky sharks displayed variable connectivity, preferring natural banks in winter and spring and year-round presence at artificial reefs in summer. Conversely, sandbar sharks showed consistent, year-round presence across both natural banks and artificial habitats, with 46% of detected individuals observed beyond the FGBNMS acoustic network compared to only 9% of detected silky sharks. Discussion These findings expand our understanding of species habitat linkages and demonstrate that sanctuary banks, non-sanctuary banks, and artificial reefs collectively constitute interconnected habitat use that is integral for two highly migratory shark species in the Gulf of Mexico.