ABSTRACT:

Wildlife tourism often uses food-based attractants to aggregate focal species. While this can adversely affect the focal species, there is limited understanding of its effects on non-focal species which often also respond to the attractant. At the Neptune Islands, South Australia, bait and berley are used to entice white sharks Carcharodon carcharias to cage-diving vessels, inadvertently attracting and feeding silver trevally Pseudocaranx georgianus. Feeding on the bait and berley affects their diet, but it is unknown whether it also affects their movements, behaviour, and energy budgets. We used a fine-scale acoustic telemetry array to monitor the movement and activity (i.e. proxy for energy expenditure calculated from three-dimensional acceleration) of 25 tagged silver trevally in response to white shark tourism. The presence of cage-diving operators increased residency across weekly (32%) and daily (20%) scales, while reducing the core space by aggregating them at the surface (<5 m), close to food-based operators. Despite observations of silver trevally bursting towards tethered baits, changes in activity (acceleration, m s^–2) were minimal compared to non-operator days. While food was available near daily, a thermally triggered seasonal exodus by 76% of individuals indicates silver trevally still undergo natural movements and behaviours. However, the supplemental nutrients and substantial time spent at Neptune Islands has potential to alter the energy budgets of silver trevally. Findings reveal the impacts provisioning from wildlife tourism can have on non-focal schooling pelagic fish, supporting the need for management of wildlife tourism to account for the whole ecosystem when assessing the ecological sustainability of a tourism industry.