Developing the use of drones for non-destructive shark management and beach safety

Andrew  Peter Colefax

doi:10.25918/thesis.55

There is an increasing need to address human-wildlife conflict in ways that support conservation. However, this is seldom achieved. Shark bites are a well-known human-wildlife conflict, which has presented many management challenges. White (Carcharodon carcarius), bull (Carcharhinus leucas) and tiger (Galeocerdo cuvier) sharks are responsible for the majority of shark bite incidents, both in Australia and globally. Traditionally, addressing perceptions of shark bite risk from these species involved lethal approaches (e.g. mesh nets and drumlines). However, social attitudes are changing towards having greater conservation sentiment, and the cost to wildlife of lethal strategies is increasingly criticised. Therefore, there is widely acknowledged need for a reliable alternative to mitigating shark bites that does not impact marine wildlife. Drones (unmanned aerial vehicles) may contribute to a solution that reduces shark bite risk to a socially acceptable level. However, their functionality for use as a shark bite mitigation tool needs to be optimised. This research critically assesses the utility of drones to detect sharks and other marine fauna, and investigates pathways for improving their reliability and efficiency as a mitigation tool. Specifically, we conclude that: (1) Drones are an efficient marine survey platform over small spatial scales of a few kilometres, and have the capacity to improve functionality through automation and further technological developments; (2) Drones are an effective aerial surveillance platform across a range of environmental conditions, with reliability of field-based detections seen to be affected by water clarity and the perceived contrast of target animals against their surrounds; (3) While drones may incur a degree of error with regards to detection rates, the indication of white, bull, and tiger sharks ~ 500 m offshore by other technologies do not reliably translate to a measure of potential threat near the surf break. This reinforces the need for better understanding of the localised distributions and behaviour of relevant shark species when considering non-destructive mitigation; (4) When white sharks venture near surf breaks, they typically swim slowly (~ 0.83 m s1 or 3 km h-1) and parallel to the shoreline, which highlights the potential utility of drone surveillance for intercepting white sharks that may pose a hazard to bathers; and (5) By restricting spectral input to the camera sensor of the drone to focus on wavelengths between 514– 544 nm, the perceived contrast of sharks and other fauna from their surrounds should markedly increase, which would improve detection reliability of drone-based surveillance. Overall, drones have potential to contribute to effective shark bite management strategies that do not require culling sharks or impacting bycatch species commonly affected by lethal strategies. Furthermore, due to the rapidly advancing development of drone-related technologies, the utility of drones for reducing the risk of shark bites can be further improved upon.

Developing the use of drones for non-destructive shark management and beach safety

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Developing the use of drones for non-destructive shark management and beach safety

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