Background Information
Stock condition
Bigeye tuna in the WCPO is caught mainly by two industrial gears that target different parts of the population. Longline vessels from fleets such as Japan, China, Korea, and Chinese Taipei focus on deeper‑swimming, larger (adult) fish for the sashimi market. Purse‑seine fleets, many of them Pacific Islands vessels alongside Japan, Korea, Chinese Taipei, and the United States, catch bigeye mostly as juveniles when setting on drifting fish‑aggregating devices (FADs) while targeting skipjack tuna. In Southeast Asia, “other” gears (e.g., handline and ringnet) also take small bigeye around anchored FADs.
The latest year with a full overview (2024) shows a mixed picture. Total bigeye catch in the WCPF Convention Area was provisionally ~119,000 tonnes (about 4% of total tuna), representing one of the lowest levels since the 1990s. Purse‑seine caught bigeye was about 34,000t, the lowest since 1990, reflecting more free‑school fishing (which avoids FADs and catches fewer juvenile bigeye). Longline bigeye was roughly 48,000t, also near multi‑decade lows.
Current fishery status
Even at lower volumes, bigeye is economically important because larger fish fetch premium sashimi prices. In 2024, the delivered value of the bigeye catch was about US$508 million, though that was down about a quarter on the previous year due to softer market prices. This value makes bigeye a critical species for longline fleets.
Importance of the Fishery
The estimated 2024 value of the WCPO bigeye catch was approximately US$508 million (≈9% of total WCPO tuna value), down about 26% from 2023. BET is a high‑value sashimi species and historically commands the highest prices among tropical tunas on the Japanese market, hence longline BET remains economically pivotal despite lower volumes.
Science
Stock status – latest assessment
The 2023 stock assessment (most recent) concluded that WCPO bigeye is not overfished and not experiencing overfishing. In more intuitive terms, the “breeding potential” of the stock is estimated to be about 35% of what it would be without fishing, which is above the Commission’s limit reference point (20%) and meets today’s interim management objective (to stay at or above the 2012–2015 level, ~34%). Recent fishing pressure was estimated at about 60% of the level that would cause long‑term overfishing. These results are robust across many model variants, though they are naturally sensitive to how the model treats things like tag data and the biology of the stock.
A few long‑running patterns underpin that headline: depletion increased up to around 2010, then stabilized; and juveniles have consistently faced higher fishing pressure than adults, largely because FAD sets take small fish.
Scientific advice to managers
Because the next bigeye stock assessment will not take place until 2026, the WCPFC Scientific Committee compiled short‑term indicators and projections. Those indicators show a temporary uptick in the “fishing pressure” metric—with a median F/FMSY ≈ 1.67 and a 91% chance that recent fishing exceeded the level associated with MSY; but biomass is still projected to stay well above the limit (only ~2% risk of dropping below it in the near term). Importantly, scientists advise vigilance and to not confuse the current fishery indicators with a new stock assessment.
The Scientific Committee also flags data issues that make these indicators harder to interpret, for example the continuing challenge of pinning down species composition in purse seine FAD sets, which matter most for estimating juvenile bigeye removals.
How does the WCPFC manage the bigeye fishery?
Current management framework
The Commission’s tropical tuna measure (CMM 2023‑01) sets an interim objective for bigeye: keep spawning biomass at or above the 2012–2015 average until a full harvest strategy is adopted. To control juvenile catches in the purse‑seine fishery, the measure includes a 1½‑month FAD closure every year (1 July–15 August, 20°N–20°S), plus one additional month of FAD closure on the high seas chosen by each flag CCM (April, May, November, or December). There is also a cap of 350 active drifting FAD buoys per vessel, and the Commission has set a pathway to biodegradable FADs by 2026. For longliners, flag‑specific bigeye catch limits apply, with monitoring and pay‑back provisions for overages. The measure also recognizes the tight coupling between skipjack, yellowfin, and bigeye in purse‑seine operations, so settings for one species can’t be made in isolation.
Management issues
Two issues dominate management of the WCPO bigeye stock. First, juvenile mortality from FAD sets: because purse‑seine bigeye catch is almost entirely from FAD‑associated sets, the effectiveness of closures, buoy caps and any future FAD standards is central to keeping bigeye healthy while still meeting skipjack objectives. Second, data and monitoring: observer coverage on longliners is very low (about 3–5%), which makes it hard to independently verify that fleets are staying within their flag‑specific bigeye catch limits. The Commission is trying to mitigate that risk by (i) tying any optional catch‑limit increases to higher observer/EM coverage, and (ii) improving data flows so longline logbook catches can be cross‑checked against transshipment and other independent sources. On the purse seine side, with observer coverage having dipped during the pandemic and only partly rebounded, electronic monitoring and better reporting standards are being developed to ensure science and compliance can track real impacts, especially species composition in FAD sets and catches in small‑scale “other” gears. The Scientific Committee closed out its long‑running “Project 60” on purse‑seine species composition and is now steering effort to practical, scalable data streams (including cannery receipts and FAD logbooks) that the Commission can actually implement.
Improving Future Management
Managers are already moving toward harvest strategies, which are pre‑agreed rules that automatically adjust fishing as stock status changes. For bigeye, that means settling on a target reference point and a management procedure that can balance the multi-species fishery reality (skipjack, yellowfin and bigeye interact in purse‑seine sets). Until that machinery is in place, the science suggests a cautious approach: keep overall fishing pressure near current levels that have met the bigeye objective and be cautious about “fully utilizing” capacity increases that, in modeling exercises, push bigeye below the objective and raise risk. The Commission has also set a 2026 timeline to lock in hard high‑seas limits for purse‑seine effort and to update longline bigeye limits, alongside clearer rules for tracking, reporting, and auditing FAD use (including movement toward biodegradable FADs). Delivering those decisions on schedule and scaling up EM/observer coverage so data gaps don’t obscure trends, are the practical steps that will keep bigeye on a safe trajectory.
Take-home: Right now, the WCPO bigeye tuna stock is in acceptable biological shape; the latest full assessment (2023) says the stock is healthy relative to the Commission’s limits and interim objective. But juvenile catches in FAD sets remain the pressure point, and data quality and coverage in the longline fishery still need strengthening. Keeping both purse‑seine and longline impacts under control, finishing the harvest strategy for bigeye, and delivering the 2026 decisions on limits and FAD reforms are the keys to keeping risk low while maintaining value for fleets and Pacific Island economies.