An initial exploration of cetacean bycatch and interactions in the WCPFC

Masere (Miller) C, Baird K (2023) An initial exploration of cetacean bycatch and interactions in the WCPFC. In: WCPFC Scientific Committee 19th Regular Session. WCPFC-SC19-2023/EB-WP-08, Koror, Palau

A recent review of cetaceans in the Pacific Islands Region indicated there are at least 34 species that are resident, migrant or vagrant within this region and they face a variety of threats including incidental catch and fishing gear interactions; harvesting (direct take); pollution; vessel traffic; pathogens and introduced species; resource depletion; and ocean-physics alteration, including climate change. Of these threats, bycatch and interactions with commercial fishery vessels appears to be the most serious. An initial analysis from publicly accessible data covering 2013–2020 and also extracted from SPC summary reports suggests that in the purse seine fishery the species with the highest reported rates of interactions are false killer whales, short-finned pilot whales, roughtoothed dolphins, bottlenose dolphins and spinner dolphins – and in the longline fishery that the species most frequently interacting are false killer whales, bottlenose dolphins, and other toothed whales.

However, there are numerous caveats and limitations to this data including: uneven effort, coarse spatial and temporal resolution of the data, not all data is included (for longline there was an average of 2.5% observer coverage and 75% of effort available; for purse seine there was an average of 87% observer coverage and 55% of effort available), there are some issues with taxonomic classification and groupings, and changes in conservation management measures over time likely have had an impact on reporting rates and fishing activities. Some initial suggestions on how to progress this work in order to gain a better understanding on the scope and extent of the issue include more targeted training and resources for observers, review of historical data to guide future refinements and improvements in quality control and reporting by observers, introduction of single species and taxonomic-specific statistical modelling approaches, and a more substantive and finerscale statistical analysis of relevant data.