The tuna fisheries of the western and central Pacific Ocean (WCPO) are in better shape than those of other oceans, a report just published by the International Seafood Sustainability Foundation (ISSF) shows.

The report summarises the state of health of the world’s tuna fisheries. It covers 23 tuna stocks: 6 albacore, 4 bigeye, 4 bluefin, 5 skipjack, and 4 yellowfin stocks. All but bluefin are commercially important in the WCPO.

The report is compiled from official reports of the 5 regional fisheries management organisations (RFMOs), including the Western and Central Pacific Fisheries Commission (WCPFC), which manages the tuna fisheries of the WCPO.

It backs up research by the Pacific Community that compares the status of tuna populations in the western Pacific, eastern Pacific, Atlantic and Indian oceans. The WCPO is the only area of ocean in which all four tuna are abundant and are not overfished.

Graph of numbers of four species of tuna in eastern Pacific, western Pacific, Atlantic and Indian oceans, and state of health of tuna populations using green, yellow and red code. Graph: Pacific Community
Tuna populations in the WCPO (second column) are much healthier than in other oceans. Catch and stock status for albacore (ALB), bigeye (BET), skipjack (SKJ) and yellowfin (YFT) tuna in the eastern Pacific Ocean (EPO), western Pacific Ocean (WPO), Atlantic Ocean (AO) and Indian Ocean (IO). Figure: Pacific Community.

Although the ISSF report shows that tuna are abundant enough in the WCPO to be able to withstand fishing at current levels, it points out that there is “no potential” to increase fishing for yellowfin because it is “fully exploited”.

ISSF rated each of the 23 global stocks using 3 factors: abundance, fishing mortality, and environment. Each factor is colour-coded green (good, sustainable), yellow (warning, borderline) or orange (unsustainable or insufficient management).

Abundance relates to not just to populations numbers, but also looks at whether fish have been allowed to grow and reproduce at their most productive level.

Mortality is a measure of how intense the fishing effort is, and is a way of understanding whether a population is being overfished.

Environment refers mostly to action to minimise bycatch, species such as sharks, turtles and seabirds, as well as juvenile tuna, that aren’t targeted for fishing but end up in the catch. Some species face extinction, partly as a result of commercial fishing. Bycatch is usually noted accurately when it the catch is monitored independently.

Need to improve harvest controls and monitoring of longline fishing

The report shows that all RFMOs need to manage stocks better, even where tuna are abundant.

ISSF’s particular focus was harvest controls. Although there are no binding target reference points (TRPs) or harvest controls in the WCPO yet, it notes that a few conservation and management measures (CMMs) include interim targets. CMM 2014-06 calls for harvest strategies for each kind of tuna and lists the elements that should be included. CMM 2015-06 sets an interim TRP for skipjack tuna.

CMM 2020-01 contains bridging rules for bigeye, skipjack and yellowfin that include benchmark numbers (expressed as spawning biomass) to be maintained. However, ISSF said that this CMM was too complex because it included “many ‘either/or’ choices, exemptions or exclusions” and that decisions were yet to be made about some measure. These made it “impossible to predict the outcomes in terms of actual future catch and effort levels”.

WCPFC is not alone: there are few TRPs and harvest controls operating in other oceans either.

The other major concern noted in the report is the lack of independent monitoring of longline fleets, which ISSF labelled as “deficient” in all oceans and among nearly all fisheries where longline fishing occurs. Without monitoring, it is impossible to know how much wildlife becomes bycatch. Longline fleets are notoriously difficult to monitor.

Strengths of WCPFC management also noted

The report notes that the interim arrangements to control the tuna harvest in the WCPO are “robust” and “ensure the sustainability of bigeye, skipjack and yellowfin tuna stocks”. They include:

  • banning the use of fish-aggregating devices (FADs) from 1 July to 30 September each year, between the latitudes of 20 °N and 20 °S, in both exclusive economic zones and high seas
  • imposing an additional FAD closure of 2 months
  • requiring that all FADs prevent the entanglement of sharks, turtles and other species
  • limiting the number of drifting FADs, fishing days and, for some vessels, freezing capacity
  • requiring that all fish caught be retained, even if they have no market value or haven’t been targeted for fishing
  • requiring that all purse seine vessels have an independent observer on board.

ISSF reports that the global catch of albacore, bigeye, bluefin, skipjack and yellowfin in 2019 was 5.3 million tonnes. It said that 65% of stocks of tuna were at healthy levels of abundance, 13% were overfished, and 22% were in between.

Worldwide, 87.6% of the catch was from healthily abundant stocks.

About 52% of the world’s production of tuna was from the WCPO.

The report, Status of the world fisheries for tuna: March 2021, can be downloaded from the ISSF website.