Quantifying shark depredation events while commercial, charter and recreational fishing in Western Australia

Shark encounters while fishing in Western Australian waters have been perceived to be increasing by some fishers in recent years. A lack of quantitative information remains a significant obstacle to determining the nature and magnitude of these encounters. A probability-based survey was implemented to assess the occurrence of and attitudes toward shark encounters by commercial fishers, charter tour operators and private boat-based recreational fishers during 2015/16. Of the 906 fishers interviewed, 52% indicated they had experienced at least one shark encounter while fishing during the previous year. The loss or damage of fish was involved in over half of these encounters while charter fishing and nearly a third while recreational fishing. The level of concern towards shark depredation was highest among charter tour operators state-wide and all sectors in the Gascoyne bioregion. Multiple logistic regression analyses indicated fishing method and bioregion were the most important predictors of encounters. Depredation through fish loss below or at the surface was highest for pelagic or demersal line fishing in the North Coast and Gascoyne bioregions. Overwhelmingly, the majority of fishers in all sectors were satisfied with their fishing experience despite the occurrence of shark encounters. Future research on shark depredation would benefit from focusing on fishing methods and bioregions where depredation events were highest, with consideration of associated behavioural and environmental characteristics likely to influence depredation rates. The approach outlined here could easily be applied to other human-wildlife interaction studies where representative views of stakeholders are required for policy development and effective management.