Morphological characterization and hydrodynamic behavior of Biscay Bay’s mako shark (Isurus oxyrinchus) dorsal fin denticles

Supervisors: Manu Soto, Jesus Mari Blanco (UPV/EHU)
The shortfin mako shark (Isurus oxyrinchus) is considered one of the fastest marine fishes, reaching speeds of up to 70 km/h. This speed is higher than what would be expected from the physiological and muscular capacities. This particular hydrodynamic efficiency is closely related to the design of the skin surface composed of tiny dermal denticles whose design is species specific. Denticles can vary in size and shape according to placement on the body and act by breaking the boundary layer of water in contact with the skin minimizing the turbulence around the body and thus reducing the drag in swimming. The hydrodynamic effect of the configuration and morphology of denticles is thought to be responsible for the high swimming efficiency of Mako sharks compared to other species of shark. In recent years artificial coats/films bioinspired on shark-skin scales have been tested in experimental conditions on aircrafts and vessels and have shown interesting aero-hydrodynamic properties. In this investigation, individuals of the pelagic shark Isurus oxyrinchus were obtained from licensed vessels fishing in the Bay of Biscay. The morphology, density, and orientation of the denticles of the dorsal fin were calculated. 3D reconstruction of the denticles on the dorsal fin was performed. Afterward, computational fluid dynamics (CFD) using STAR CCM+ software was applied. Simulations of fluid passage over reconstructed denticles were carried out to describe the hydrodynamic efficiency in different conditions and scenarios. The main conclusions of this work can potentially be applied to hydrodynamic structures like boat hulls to also increase their efficiency.