Smith, Kirby (2016) Behavioural ecology of the critically endangered grey nurse shark (Carcharias taurus) and the interaction with scuba diving tourism off eastern Australia. PhD thesis, Victoria University.

Abstract

The critically endangered grey nurse shark (Carcharias taurus) off eastern Australia is the focus of a non-consumptive, economically important marine wildlife tourism (MWT) industry centred on scuba diving with the sharks. This industry has been identified as a potential threat to the continued survival and recovery of the species. Legislative guidelines and a national code of conduct for scuba diver behaviour were developed to mitigate adverse impacts of MWT on the sharks. This research assessed the putative impacts of scuba diving MWT on grey nurse shark behaviour and the efficacy of management strategies across differing life-history stages and aggregation sites. Underwater stereo-video photogrammetry was used to develop a partial ethogram of the swimming and non-swimming behaviours of grey nurse sharks at locations within aggregation sites during daylight hours without MWT. Predominantly low-energy behaviours were exhibited and no threatening agonistic behaviours were observed. Underwater visual census also documented primarily low-activity swimming behaviours in sharks during interactions with MWT scuba divers of varying demographics and revealed absolute diver compliance with management guidelines. Passive acoustic telemetry showed sharks may have exhibited more active swimming when patrolling between two locations within a site but adopted low-energy swimming behaviours for the majority of the time during daylight hours regardless of scuba diving MWT. Sharks at differing life-history stages probably conserved energy at aggregation sites in association with their migratory movements and reproductive cycles. Differences in the swimming and patrolling behaviours of sharks were attributed to natural variation in environmental conditions (i.e. topography and currents) at the sites as they were not consistent with scuba diving MWT activity. This research strongly suggested that management strategies are effective at protecting the east Australian population of grey nurse sharks from MWT disturbance. Consequently, the grey nurse shark scuba diving MWT industry in its current form is ecologically and economically sustainable.

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