FINE-SCALE MOVEMENT PATTERNS OF THE BLACKTIP SHARK AT A MIGRATION TERMINUS

Many marine species make use of the expanse of the ocean by traveling great distances to fulfill life history requirements. The blacktip shark, Carcharhinus limbatus, is a medium sized species associated near the coast found circumglobally in temperate waters. In the northwestern Atlantic Ocean, blacktips migrate in large aggregations along the eastern coast of the United States annually from the Carolinas in the summer months to a terminus in southeastern Florida in the winter. What daily movement patterns these adult sharks undergo during their multi-month residency at this southern terminus has largely been unquantified. I employed fin-mounted accelerometer tag packages to record high-resolution data from multiple blacktip sharks (n=8) during their winter residency in southeast Florida. Diel variation in behavior through depth range and the swimming kinematics were analyzed, while pseudo tracks were reconstructed to visually inspect post-release movement. Depth did not show significant variation between diel periods using a mixed model, with individual mean depths ranging from 1.43 – 39.20 m. Velocity was lower than expected for comparative studies of sharks, where overall mean values ranged from 0.15 – 0.93 m s-1. Diel period velocity comparison was also found to be insignificant. Tail beat frequency was found to have a group mean of 0.72 Hz, similar to other studies using different methods of the same population. The subset of tags analyzed for pseudo tracks (n=3) showed a swim away from the catch event towards the east. This data adds to the knowledge of blacktip shark movement, and contributes to the baseline comprehension of a population that is an important coastal fisheries species.