Integrated approach to assess the spatio-temporal foraging dynamics of a temperate marine predator, the copper shark (Carcharhinus brachyurus)

Large-bodied sharks can be critical for coupling disparate habitats and food webs, which is considered central for ecosystem stability. Understanding the role of sharks and their associated predator-prey relationships across spatial scales is also integral to the development of multi-species ecosystem models. A combined stomach content (n = 212) and multi-tissue stable isotope (fast [liver; n = 101] vs slow turnover [muscle; n = 108]) approach was used to investigate the feeding ecology of the copper shark (Carcharhinus brachyurus) in the temperate waters of Southern Australia. Sharks were sampled from fishery catches over 3 years, during the austral spring-summer seasons and across three distinct regions. Stomach content analysis identified the copper shark as a generalist predator that consumes a diverse prey base dominated by Sepia novaehollandiae, Sepioteuthis australis, and Sardinops sagax (36%, 21%, and 18% IRI). Regional differences in diet composition were evident, although no size- or sex-based variation was identified. Isotope mixing models and regional food web bi-plots also revealed that S. sagax was the most important prey species, but temporal variation in diet was observed that matched known movements. The copper shark was estimated to be a primary piscivore, feeding at trophic level 4.49. Data on the feeding behaviour of copper sharks will provide vital inputs into future ecosystem-based fishery models and guide conservation and management of this important marine predator in temperate Southern Australian coastal waters.