Meeting Abstract
Fish gain hydrodynamic benefits such as increased swimming efficiency when schooling. The group structure, or arrangement within a school, necessary for increased efficiency is modeled as four animals in a diamond formation, but this hypothesis has not been tested in the wild. Previously, we quantified wild Carcharhinus limbatus, blacktip sharks, volitional swimming kinematics and found individuals traveled in groups of 4, in a diamond formation, and had significantly lower Strouhal number values when compared to other group sizes. Here, we examine hydrodynamic models produced by our volitional swimming kinematics data. We utilized an aerial drone to capture footage of wild, straight swimming C. limbatus in various group sizes and used motion tracking software to examine kinematic variables (tailbeat frequency, amplitude, velocity, and Strouhal number). ImageJ was used to quantify nearest-neighbor distance, school density, orientation angle, and position within a formation from still photos. Kinematic data were then used as inputs for numerical simulations solving the Navier-Stokes equations to examine wake produced by varying group sizes (2-12 sharks). Reynolds’ flocking models were used to assess coordination among sharks within a school. Our results indicate that individuals within a group are placed to interact constructively with wake, and coordinated movement exists within pairs of individuals. This work provides validation to previous mathematical simulations from the literature conducted on hydrodynamics of collective formations, and insight into priorities of schooling arrangements in the wild.
