Electronic pulse device deters and delays shark feeding in a depredation context

Abstract

Fishers losing their catch or gear to marine predators (‘depredation’), including sharks, is a growing problem around the world. Several types of devices have been tested to deter sharks from engaging in depredation but with limited success. Captive bonnethead sharks, Sphyrna tiburo L. 1758 (N = 8), were used to test the effectiveness of a recently developed electronic pulse device (EPD) to deter or delay shark depredation. Individuals were paired and exposed to either an active (battery in) or inactive (battery out) EPD connected to bait on a rod and reel (N = 198 paired trials). When an active EPD was used, the bait was ingested in 46.4% of the trials compared to 92.1% of the trials when an inactive EPD was used. When the bait was ingested, the sharks took significantly longer to feed when using the active EPD than when using the inactive EPD (Wilcoxon rank-sum test, p < 0.001). Individuals exhibited significantly more ‘rapid withdrawal’ responses to the active EPDs compared to the inactive EPDs (Fisher's exact test, p < 0.001). EPDs show promise to deter or delay sharks from feeding for a short period and may therefore be an effective tool for reducing depredation in situations where catches are quickly pulled from the water (e.g. rod and reel, handline, pole-and-line fisheries).