WCPO bigeye and yellowfin tuna stocks remain healthy

Categories News, NewsPosted on
Yellowfin tuna in the Pacific Ocean. Photo: WWF.

Republished from FFA Trade and Industry Newsvolume 13, issue 4, July–August 2020

WCPFC’s 16th Scientific Committee (SC16) was held virtually from 12–19 August 2020. During this meeting new WCPO bigeye and yellowfin stock assessments were presented by the Secretariat of the Pacific Community (SPC), indicating that both stocks remain healthy.

The previous full stock assessment for bigeye was conducted in 2017. It indicated a positive change in WCPO bigeye stock status to ‘healthy’ from ‘overfished’, with overfishing occurring. For the 2020 assessment, median values of relative recent spawning biomass (2015–2018) and fishing morality (2014–2017) indicate that the bigeye stock remains not overfished (with 100% probability) and likely continues to not be experiencing overfishing (with 87.5% probability).

However, levels of bigeye fishing mortality and depletion differ among the nine regions used in SPC’s stock-assessment models, with higher impacts in the four tropical regions, particularly on juvenile bigeye. Hence, overall bigeye stock status is buffered by lower catches in the temperate regions.

Similarly, the 2020 stock assessment indicates that the WCPO yellowfin stock is not overfished, nor subject to overfishing (both with 100% probability). Like bigeye, yellowfin exploitation is higher in tropical regions where fishing effort is concentrated by the equatorial purse-seine fishery and ‘other’ fisheries (e.g. pole-and-line and handline vessels operating in Indonesia); there is low yellowfin exploitation in temperate regions.

Hence, for both bigeye and yellowfin, SC16 recommended that WCPFC17 continue to consider management measures that reduce fishing mortality from fisheries that take juveniles (i.e. purse-seine fishery) to increase bigeye and yellowfin fishery yields and reduce any further impacts on spawning biomass in the tropical regions.

SC16 also recommended that a precautionary approach be maintained, with bigeye and yellowfin fishing mortality kept at a level that maintains spawning biomass at 2012–2015 levels until the Commission can agree on appropriate target reference points (i.e. the optimal level of spawning biomass or fishing mortality that ensures long-term sustainability of the stock).

The WCPO continues to be the only ocean where stocks of the four key tuna species – skipjack, yellowfin, bigeye and albacore – are deemed to be in a healthy state.