Shark behaviour and marine faunal assemblage beneath SMART drumlines

Abstract

Over the last decade, an increase in the annual rate of shark bites on people has stimulated the development of new techniques aimed at reducing their occurrence, while minimising negative impacts to marine wildlife. One such technique is the SMART (Shark-Management-Alert-in-Real-Time) drumline, which allows for the capture and relocation of white sharks (Carcharodon carcharias), bull sharks (Carcharhinus leucas), and tiger sharks (Galeocerdo cuvier), the species responsible for most of the fatal shark bites on people. Over a 12-month period, we assessed the marine faunal assemblages observed in >1200 deployments of high-definition video cameras beneath SMART drumlines. Shark behaviours around SMART drumlines were also quantified. The faunal assemblage around the SMART drumlines was characterised by low richness, dominated by schooling bait fish, and influenced by sea surface temperature. Few non-target species of conservation concern (e.g. sea turtles, hammerhead sharks, or critically endangered greynurse sharks) were observed. Of the sharks approaching the drumlines, white sharks were more likely to bite and subsequently remove bait, leading to more instances of successful capture and release, and a greater rate of depredation. However, instances of depredation during the program were low and only occurred in 13 % of all shark bite interactions. Our results provide support for the use of SMART drumlines as an efficient tool for catching target shark species with minimal impact on non-target fauna.