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

Juxtaposing zinc and graphite together produces a galvanic electric field
in seawater that may deter electrosensitive species, and thus reduce
elasmobranch capture on longlines. The number of coastal carcharhiniform
sharks caught on untreated and procedural control treatments did not
differ, but significantly fewer sharks were caught on the zinc/graphite
treatment (14.5%) compared to the procedural control (38.4%) and the
untreated hook (47.1%). This translates to a 62.3-69.5% reduction in
sharks caught on the zinc/graphite treatment. There was no significant
difference in catch among the zinc/graphite and control treatments for
piked dogfish. Too few sharks were captured in the pelagic trials to allow
statistical comparison; however, capture of targeted bony fishes was
highest on hooks with the zinc/graphite treatment, suggesting no negative
effect on target catch rates. The difference in efficacy between
carcharhiniform sharks and dogfish indicates the behavioral response to
this deterrent may vary among elasmobranchs. Large-scale testing of the
zinc/graphite treatment in pelagic fisheries is needed to establish
whether it is a viable option to reduce shark bycatch and increase
profitability in commercial fisheries.