Forget et al, 1 September 2021
Mitigating bycatch is a key to sustainable fisheries, and to assess the impact of a fishery on bycatch species, is a necessary first step. In Tuna purse seine fisheries, pelagic sharks account for about 1% of total catch by weight, including the silky shark and oceanic white tip, both of which are listed under CITES Appendix 2 and Vulnerable by the IUCN. Currently, many vessels have only one observer on board, making it challenging to get an accurate count on bycatch. This study set out to study the variation between the current single observer system, EMS and their system with multiple observers strategically placed. They found that ‘shark counts were underestimated for 50%–100% of the sets, with the mean shark count underestimation, at the fishing trip level, ranging from 9% to 40% (onboard observers) and 65% for EMS.’ The authors highlight that there are many factors which could impact this underestimation, both from onboard observers and EMS systems, and that this likely varies by fishery, and recommend additional studies comparing EMS, single observers and a methodology such as theirs which includes multiple strategically placed observers to further explore bycatch estimates.
Our thoughts: This is a great example of why we need more and better data from fisheries using a combination of onboard observers and EMS systems. It also highlights the current shortcomings in MSC’s current scoring requirements for data availability which are not driving best practice, and largely ignore the reality on the water.
