Japan’s Fisheries Agency has presented a proposal to the Northern Committee of the Western and Central Pacific Fisheries Commission (WCPFC) to increase the catch quota for both adult and juvenile (under 30-kilogram) Pacific bluefin tuna. The proposal cites a recovery trend in the stock of adult fish with spawning ability, called “spawning stock biomass (SSB)."
The committee is scheduled to meet electronically on 8 October. The panel of 10 members representing member-nations makes recommendations to the WCPFC regarding the management of Pacific bluefin tuna. If the proposal is approved, Japan’s quotas will be increased by 801 metric tons (MT) for juvenile tuna and by 976 tons for mature tuna.
The proposal is in accordance with Paragraph 5 of the WCPFC’s Harvest Strategy for Pacific Bluefin Tuna Fisheries, which relates to decision-making rules for setting quotas. During the current initial rebuilding period, the interim harvest control rules are to be applied based on the results of stock assessments and SSB projections conducted by the International Scientific Committee (ISC).
If the SSB projection indicates that the probability of achieving the initial rebuilding target of 40,000 metric tons by 2024 is 75 percent or larger, the WCPFC may increase catch limits as long as the probability is maintained at 70 percent or larger, and the probability of reaching the second rebuilding target by the agreed deadline remains at least 60 percent.
An assessment earlier this year by the ISC for tuna and tuna-like species in the North Pacific Ocean determined that the probability of achieving the recovery target for Pacific bluefin tuna, even with a 20 percent increase in the quota (as in Japan’s proposal), would be 99 percent. The SSB would then be expected to increase to a median level of 85,618 MT. The SSB in 2018 was 28,228 MT.
Last year, a similar recommendation was rejected by the United States, but the probability assessment has improved since then. Japan now has a stronger case that it says is supported by science and the rules of the harvest strategy. Harvest strategies are meant to take the politics out of this sort of decision-making by setting the rules in advance and under the 70 percent threshold, the increase should be approved, according to the Japanese delegation.
It is possible that other members will take issue with another part of Japan’s proposal, which is to introduce a conversion factor of 1.46 that would allow a higher harvest of juveniles. The amount over the quota would be subtracted from the quota for adults. The Japanese proposal states that the catch of age 2 PBF [Pacific bluefin tuna fishery], the largest cohort in PBF smaller than 30 kilograms, is estimated to have 1.46 times larger impact on biomass than that of age 3 PBF, the smallest cohort in PBF 30 kilograms or larger.
Japan has had trouble managing bycatch of juvenile bluefin, which has become a choke species that threatens to shut down other fisheries when the limits are reached.
The Pew Charitable Trusts, based in Washington, D.C., which holds observer status at the WCPFC, submitted a statement to the committee on 28 September that recommends maintaining the existing catch limits, consistent with a precautionary approach. It also promoted the development of a Management Strategy Evaluation (MSE) for Pacific bluefin. The WCPFC is working on implementing an MSE for bluefin, but progress has been slow.
“[A] MSE is critical for managers to adopt scientifically-tested, long-term targets and harvest control rules to modernize management of this important fishery and ensure its sustainability into the future,” the statement said. “The current ‘harvest strategy’ does not qualify as a harvest strategy.”
