Meeting Abstract
Southeast Florida’s marine ecosystem experiences a seasonal influx of upper trophic level predators each winter due to the large-scale annual migration of blacktip sharks (Carcharhinus limbatus). Blacktip sharks occupy shallow, coastal habitats and are distributed from Georgia to North Carolina during the late spring and summer, migrate south during the fall to overwinter in Florida, and then migrate north in late winter and early spring. As they migrate, blacktip sharks form dense aggregations along Florida’s coastline. Although these large shark aggregations attract significant public interest, surprisingly little empirical data have been collected on the shark abundance, spatial distribution, and the factors driving their migration. Manned aerial surveys of coastal waters were conducted from Boca Raton to Jupiter (2011-2014), and Miami to Jupiter (2015-2018). A high definition video camera mounted out the open window of the plane recorded the transect to a distance approximately 200m seaward of the beach. These videos were analyzed to determine blacktip shark abundance, and shark densities within inlet-bound sections of the coastline. Water temperature was also recorded to examine correlations with shark abundance. Results indicate that the highest shark densities, exceeding 2,000 sharks km-2, were in the northern-most sections of the transect (Palm Beach County) in February and March, when water temperature was at its lowest. Peak shark abundance was significantly inversely correlated with water temperature. This strong correlation between water temperature and shark abundance suggests that warming oceans might shift the southern terminus of the migration towards higher latitudes, causing ecological changes along the United States Eastern seaboard.
