In the spotlight

Congratulations to Jem Turner, 2017 Ernest Hodgkin awardee

Jem Turner, Jessica Meeuwig | May 25, 2017

Jem Turner, Jessica Meeuwig

May 25, 2017

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Jem used baited video cameras to investigate the behaviour of requiem sharks.

Source: Centre for Marine Futures.

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Jem Turner
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Congratulations to Jem Turner, who was recently awarded the Ernest Hodgkin Memorial Prize in Marine Science in recognition of her outstanding thesis on the behaviour of elusive requiem shark species.

The prize is given to the Honours student (majoring in Marine Biology or Marine Science) with the highest marked research project.

ABSTRACT

Sharks are apex predators that play a vital role in maintaining ecosystem stability in the pelagic environment, however many pelagic species are experiencing worldwide declines in population numbers as a result of fisheries overexploitation. Consequently, understanding how pelagic sharks interact with novel stimuli may provide insight into their relative vulnerability to fishing-induced mortality and may have significant implications for shark conservation and fisheries management strategies. The inherent challenges that arise when studying large, highly mobile and predatory animals such as sharks raises the need for observational techniques that enable safe, non-invasive in situ sampling of shark behaviour. Stereo-baited remote underwater video systems (stereo-BRUVS), typically used on the seabed, have been adapted to a mid-water configuration in order to sample sharks within pelagic environments. In conjunction with an ethogram, which was developed from a combination of behaviours previously reported in the literature and from preliminary review of video imagery, this study used video footage generated by mid-water stereo-BRUVS to examine location-, species- and size-specific differences in the behavioural composition, frequency and timing for silvertip (Carcharhinus albimarginatus), grey reef (Carcharhinus amblyrhynchos) and silky (Carcharhinus falciformis) sharks observed across three geographical locations. These locations were used as a proxy for fishing pressure, as each location varied in their level of fishing protection. Within the scope of this study, size was a strong predictor of behavioural variation, where larger sharks were less diverse and frequent in their behaviours, compared to smaller sharks. Preliminary findings suggest that location and species do play a role in behavioural differences, with some evidence indicating that sharks exposed to fishing pressure are more conservative in their behaviour and that some species are more inquisitive with respect to the mid-water stereo-BRUVS. However, location and species covaried to some degree, thus attributing behavioural differences to either of these two factors must be done cautiously. Additionally, this study provides evidence that mid-water stereo-BRUVS, in conjunction with an appropriate ethogram, are capable of extracting large quantities of behavioural data relevant to the conservation of sharks in the pelagic environment.