Efficacy of a novel galvanic shark deterrent to reduce catch of elasmobranchs in longline fisheries

This study tested whether a zinc/graphite galvanic electric field reduced capture of elasmobranchs in demersal and pelagic longline fisheries in Florida and Massachusetts (United States). The catch per unit effort of demersal sharks in Florida using the zinc/graphite treatment was significantly lower than the controls, with a 62.3-69.5% reduction in sharks caught on the zinc/graphite treatment. However, there was no difference in  demersal shark CPUE between treatments in Massachusetts. Too few sharks were captured in the pelagic longline trials to allow statistical comparison; however, capture of targeted bony fishes was greatest on hooks with the zinc/graphite treatment, suggesting no negative effect on target catch rates.  Additionally, there was an observed difference in efficacy of the zinc/graphite between Carcharhiniform sharks (more effective) and the Squaliform sharks (less effective), which suggests that the response to this deterrent may be species-specific. Further testing is needed to understand the limitations of the gear and efficacy for pelagic species.