Skipjack tuna

Skipjack tuna in the western and central Pacific Ocean is not overfished or subject to overfishing.The western and central Pacific Ocean (WCPO) skipjack tuna stock is the largest tuna fishery in the world, accounting for approximately 37% of worldwide tuna landings. Catches of this stock increased steadily from 1970 onwards, reaching a record of over 2 million tonnes in 2019.The WCPO skipjack tuna fishery is managed and assessed by the Western and Central Pacific Fisheries Commission (WCPFC). The last stock assessment was carried out in 2022 using data up to 2021. The next stock assessment is expected in 2025.Spawning Biomass (SB) has declined from about 90% of unfished levels in 1970 to 51% in 2021. This is an improvement on the 2018 estimate of 44%. It is above the Target Reference Point of 40%, and well above the Limit Reference Point of 20%. Therefore, the stock is not in an overfished state.Fishing Mortality (F) has increased since the 1970s, peaking in 2018 at 45% of levels associated with Maximum Sustainable Yield (MSY). It has since declined slightly to 32%. As F is below MSY, the stock is not subject to overfishing.Trends in spawning biomass vary by region, and there is a higher depletion rate in equatorial areas. However, projections indicate that if the 2018-2021 average catch and effort levels are maintained, there is zero probability of the stock breaching its limit reference point.

Some appropriate management measures are in place to control fishing activity. However, catches have increased to record levels. Regulations have been insufficient to prevent them from increasing further and exceeding sustainable limits. However, MSC-certified fisheries are taking additional measures to control fishing activity.The majority of western and central Pacific skipjack tuna catches are independently certified to Marine Stewardship Council standards. Certified fisheries must meet additional auditing and traceability requirements that result in improved monitoring. The largest certification is the Parties to the Nauru Agreement (PNA) purse seine fishery. These South Pacific island nations have additional management beyond the WCPFC measures outlined below, including a Vessel Day Scheme that limits total fishing effort across the islands and near-real-time monitoring of effort and catch. Certifications for all the fisheries are conditional on developing Harvest Control Rules for the stock, which is dependent on action by the WCPFC. Progress on this has been made during 2023. This is detailed below, along with management measures for the wider fishery.Tuna and swordfish are highly migratory species, found on the high seas and in numerous countries' waters. This makes harmonised and effective management challenging. Regional Fisheries Management Organisations (RFMOs) are responsible for monitoring and managing these stocks on behalf of the countries that access them. However, the degree to which management is implemented, monitored and enforced by each country varies significantly. It is important that commercial buyers choose tuna that has been caught by vessels that are well regulated by their flag state.This stock is managed and assessed by the Western and Central Pacific Fisheries Commission (WCPFC). Some stocks overlap with the Inter-American Tropical Tuna Commission (IATTC). The IATTC and WCPFC endeavour to work together to promote compatibility between their respective conservation and management measures across the Pacific, but this is not always achieved.The Western and Central Pacific Ocean (WCPO) skipjack stock supports the largest tuna fishery in the world, accounting for approximately one third of worldwide tuna landings. It is not overfished or subject to overfishing, although fishing mortality is continuously increasing. The main management measure is now a Harvest Control Rule (HCR), which came into force in 2023.The HCR sets out targets to keep the stock at certain levels, and rules for deciding limits on catch and fishing effort. It aims to keep the stock size between 40% and 56% of unfished levels. The stock should also be above the point of reproductive impairment - 20% of unfished levels - with at least 80% probability. If the stock falls below 40%, fishing mortality must be reduced. Above 56%, it can be increased. Catch and effort limits will be set for 3 year periods. Changes are limited to up to 10% from one period to the next, to keep the fishery stable. Limits have not yet been published for 2023, so it is too early to tell what impact this will have on the fishery.To date, management of the tropical tuna fisheries (skipjack, yellowfin and bigeye) has primarily been by controlling the purse seine fishery. This method is responsible for around 80% of skipjack catches. The focus is on the main fishing grounds, between 20 degrees North and South, which is where fishing has the highest impact on the skipjack stock. In this area:Each country is allowed to fish for a set number of days. Fishing effort (in days) should not be displaced to other areas.Purse seiners must retain and land all bigeye, skipjack, and yellowfin tuna. This is intended to incentivise reductions in bycatch of juvenile fish.Fish Aggregating Devices (FADs) - floating objects which purse seiners use to attract tuna and increase catches - are banned from July-September. There is an additional 2-month closure in parts of the southwest Pacific islands.Vessel Monitoring System (VMS) polling, which tracks vessels using satellites, increases to every 30 minutes during the FAD closure.Observers, to verify catch and bycatch, must be on 100% of large purse seiners.In addition:Purse seine vessels are limited to 350 drifting FADs each.Each country has set its own catch or effort limits for purse seining within their own waters.Skipjack catches by other fishing gears are frozen to 2004 levels.This has not prevented catches from increasing. The catch in 2004 was 1.36 million tonnes. The 2017-2021 average is 1.75 million tonnes, with 2019 seeing the highest catch on record at over 2 million tonnes. The stock assessment indicates that fishing mortality is continuously increasing. Management has not, therefore, controlled fishing pressure on the stock.Observer coverage for other gears, including small purse seiners, and in other areas is low, at just 5%. There is not enough data to be sure that countries are complying with the management measures.To help address IUU, the WCPFC maintains an IUU Vessel List, prohibits transhipments at sea between purse seiners (some exemptions apply) and requires all other transhipments to be documented and 100% observed as part of the regional observer programme. In 2017 a Compliance Monitoring Scheme was introduced to assess and improve compliance with obligations, and penalise non-compliance.

Some skipjack tuna catches in the west Pacific Ocean are by pole & line. This is a generally low-impact method.Pole & line accounts for about 9% of the total yellowfin catch in the western and central Pacific Ocean (WCPO) (around 185,000t tonnes in 2020). This method involves fishing with rods, using live bait to attract the tuna. It targets fish near the surface, and so rarely touches the seabed, reducing the risk of habitat impacts. It is labour-intensive and very selective, meaning there are low levels of bycatch of vulnerable species.The main risk is the use of baitfish, usually small pelagic species such as sardines or anchovy. If not well managed, this can have impacts on baitfish populations.Better monitoring and data collection is required in order to monitor fishery impacts. Observer coverage in most WCPFC fisheries is just 5%, which is considered to be too low for accurate data on bycatch. A minimum of 20% coverage is recommended.Some of the pole and line catch is from MSC-certified fleets. These fleets are taking extra measures, including increased monitoring of catches and bycatch. Details about baitfish use are available for these fisheries. The majority use Japanese anchovy, which is currently overexploited. Around 500 tonnes, less than 2% of the total anchovy catch, is used as bait per year. At this level, the fishery is unlikely to be having population level impacts, but it would be preferable to use more sustainable options.Some pole and line fishing in the Pacific uses anchored Fish Aggregation Devices (FADs). FADs are floating objects that tuna and other species tend to aggregate around. In contrast with the drifting FADs (dFADs) of the major tuna fisheries, anchored FADs are less likely to be lost at sea and contribute to ghost fishing or marine debris. However, WCPFC reports that anchored FADs have a higher bycatch rate than drifting FADs, with 96.3% of the catch being tuna species as opposed to 97.9%. Most non-tropical tuna catch is other fish species, including mackerel scad, rainbow runner and small tunas. There is some bycatch of silky shark. MSC reports note that the size of the hooks used in pole and line fisheries make bycatch less likely. MSC analysis suggests that anchored FADs cover a very small area of seabed and are unlikely to have significant habitat impacts.

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