Meeting Abstract
Annually, populations of blacktip sharks (Carcharhinus limbatus) move along the coastline, forming dense aggregations at the southern terminus of their migratory route, where shallow clear water provides a unique opportunity to study swimming kinematics of large upper trophic level predator in the wild. We quantified the undulatory kinematics during straight volitional swimming of C. limbatus in varying group sizes, compared kinematics of animals within an aggregation, and quantified school shape and density. We hypothesized that the presence of isotropic schooling formations and greater animal densities enables reductions in tail beat frequency (TBF), tail beat amplitude (TBA), undulatory wave form (BC), and strouhal number (St). Furthermore, we hypothesized that sharks swimming in isotropic formations will show a reduction in TBF, TBA, BC, and St as their placement within the school moved posteriorly. We used an aerial drone and motion tracking software to obtain 4K video from schools of varying sizes. Sharks in groups were tracked to determine individual swimming kinematics, school density, and the outer perimeter of the school was traced to determine school shape. Our data suggest that sharks swimming in more dense groups have a significant reduction in St and TBF compared to sharks swimming alone. Individuals positioned posteriorly in isotropic schooling formations show a significant decrease in St and TBF. A previous study showed that increased acceleration resulted in increased metabolic rates of this species. Our data suggest there may be a hydrodynamic benefit for blacktip sharks swimming in aggregations, which may impact shark energy budgets as they engage in associative behavior and maximize efficiency in long distance migration.
