Technical mitigation measures to reduce the bycatch of sharks: there is no silver bullet

Study authors conducted a comprehensive review of technical bycatch mitigation measures for sharks for all major commercial fishing gears. Only one technique (changing fishing gear), received a “beneficial” Conservation Evidence (CE) rating (indicating a high level of certainty and effectiveness, and low probability of harm), demonstrating that no single bycatch reduction measure can be applied to all species, fishing gear, and regions. However, many different types of BRTs were rated as “likely to be beneficial”, although additional testing or information is needed. Furthermore, fishery-specific characteristics may mean that BRTs reported as effective in one area or fishery may not be as effective elsewhere. Even when a measure has been rated as being potentially beneficial, implementation in commercial fisheries may still not be feasible due to technical complexities, cost, safety issues, pollution issues, a negative impact on target catch (e.g., electropositive metals), or animal harm/welfare issues. Future research priorities should include development and incorporation of necromones (natural compounds released by decomposing organisms) into commercially viable artificial baits, production of active electrical repellents at scale to encourage uptake, investigating the impact of removal of light-sticks from longlines on shark catch rates, and refinement of circle hook design to reduce shark catch rates.