Living on the continental shelf edge: habitat use of juvenile shortfin makos Isurus oxyrinchus in the Great Australian Bight, southern Australia

Abstract

We used satellite telemetry data to investigate the movement patterns and habitat use of juvenile shortfin makos Isurus oxyrinchus (Lamnidae) tagged in the Great Australian Bight, southern Australia. Tracking durations ranged from 49–672 days and six deployments were > 1 year. During winter and spring, some shortfin makos migrated to the tropical NE Indian Ocean and Coral Sea, and the Subtropical Front region. One shortfin mako undertook an extended migration of 25 550 km across the Indian Ocean. Areas characterized by sea-mounts in the NE Indian Ocean, the oceanic Subtropical Front region, and the continental shelf edge (200-m depth) and slope canyons were visited by several sharks. Juvenile shortfin makos used the outer continental shelf, the shelf edge, the slope and oceanic waters during migrations and mostly exhibited fidelity in the mid-outer shelf, the shelf edge and slope habitats characterized by high bathymetric relief and oceanographic frontal gradients. Our findings highlighted that the continental shelf and slope and associated submarine canyons of the Great Australian Bight represent ecologically important habitats for juvenile shortfin makos. The findings of this study will be pertinent during future management processes for this highly migratory species in this Southern Hemisphere region.