Assessing the potential of bait reuse in a large-scale SMART drumline program

Abstract

Bait quality is an important characteristic that can influence the catchability of target species and contribute to sustainable fishing practices. We used bioelectrical impedance analysis (BIA) to assess the impact of various handling treatments on the quality of sea mullet (Mugil cephalus); a commonly used bait on SMART (shark-management-alert-in-real-time) drumlines in the New South Wales (NSW, Australia) shark management program. Specifically, we focused on the consequences of reusing sea mullet as drumline bait to improve the cost-effectiveness of a program incorporating 305 drumlines and spanning ∼1200 km of the east coast of Australia. After being deployed in seawater for 10 hours at 15°C, 20°C and 25°C temperatures in a flow-through mesocosm aquarium, sea mullet underwent brining, freezing, and ice storage treatments. Electrical impedance (comprised of resistance and reactance) was used as a bait quality indicator. Brining improved bait quality by reducing impedance, ice storage indicated potential quality declines while frozen baits remained stable. Resistance and reactance values of iced fish significantly increased with increasing temperature. Freezing baits showed considerable variation among resistance and reactance values. The results indicate that sea mullet could possibly be reused as bait. However, these reuse procedures now need to be tested in field trials to assess for any changes in the catchability of target sharks relative to fresh bait. We also demonstrate the utility of BIA for rapid, non-destructive assessment of bait quality.