Browsing by Author "Shale, Hannah"

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    Movements and co-occurrences of white sharks (Carcharodon carcharias) at Stewart Island, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Albany, New Zealand
    (Massey University, 2025) Shale, Hannah
    Our understanding of the fine-scale movements and behaviours of white sharks (Carcharodon carcharias) at aggregation sites is limited, yet it is central to conservation management and mitigating human-shark conflicts. This thesis examined traditionally understudied behaviours, namely individual variation in movements and sociality, to better understand the fine-scale habitat use of white sharks at Stewart Island, an aggregation site in southern New Zealand. Bayesian statistical modelling and social network analysis were used to analyse an acoustic telemetry dataset published by Francis et al. (2015), consisting of detections of 22 tagged subadult and adult white sharks by 15 acoustic receivers deployed northeast of Stewart Island during April-June 2011. The northern Titi Islands were a hotspot for white shark activity, with the highest estimated probability of occurrence (0.60) and accounting afor 89.4% of co-occurrences. Chapter 2 revealed substantial individual variation in movement patterns, with sharks exhibiting unique ‘preferences’ towards particular receivers, possibly a result of size-related behaviours like variable feeding strategies and competitive exclusion. Chapter 3 found no clear social structure and weak associations among white sharks in this study, indicating that behaviour at aggregation sites is not socially driven. That said, sharks with greater differences in body size tended to form stronger associations. This is possibly a result of smaller sharks, being considered less adept to hunting pinnipeds, associating with larger and more experienced conspecifics to exploit successful kills or to benefit from social learning. Both chapters also identified the potential influence of shark cage diving operations on the occurrences and co-occurrences of white sharks at the northern Titi Islands, particularly East Edwards Island. This thesis highlights the importance of considering white shark behaviour to obtain accurate predictions and estimates of their distribution and abundance. Incorporating measures for individual variation substantially improved model predictions of shark occurrence, and studying sociality revealed aggregations of up to seven individuals at Edwards Island. As aggregations increase the risks of fisheries-related mortality, Edwards Island should be considered for conservation efforts, such as seasonal fishing restrictions. This thesis also recommends the inclusion of individual variation in ecological modelling and further investigation of social behaviour.