Tuna, yellowfin

Thunnus albacares

Method of production — Caught at sea
Capture method — Longline
Capture area — Western & Central Pacific - WCPO (FAO 61,71,77)
Stock area — Australia and Fiji
Stock detail

Certified fleets only


Certification

Marine Stewardship Council (MSC)


Picture of Tuna, yellowfin

Sustainability rating two info

Sustainability overview

`A new stock assessment was carried out in 2017 and is similar to that from 2014 and indicating that overfishing is not occurring and the stock is not considered to be in an overfished state. The yellowfin catch for 2016 (650,491 t) was the highest recorded. The scientific committee continues to recommend measures to reduce fishing mortality on juveniles and maintain current spawning biomass levels. In 2018, the Western and Central Pacific Fisheries Commission (WCPFC) adopted a bridging measure to manage bigeye, yellowfin and skipjack (which are caught together) until harvest strategies are in place or February 2021. As part of this, spawning biomass depletion ratios for bigeye and yellowfin are to be maintained at or above recent average levels. Whiles there is no Total Allowable Catch (TAC) set for this stock, a range of measures have been implemented to try to limit catch and reduce effort. About 15% of the catch is taken in pelagic longline fisheries which can be associated with significant bycatch of other billfish and vulnerable species such as sharks, turtles, birds. Whilst there are some mitigation measures in place to reduce the impact, monitoring and reporting of interactions is insufficient to evaluate the effectiveness of these measures. There is 5% observer coverage on large longliners, but 20% is considered to be the minimum to be effective.

This rating is specific to the Marine Stewardship Council (MSC) certified fleets of Australia and Fiji. Measures in place to reduce bycatch and improved documentation and reporting enables this certified component to be better rated.

Biology

Tuna belong to the family Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Yellowfin are found throughout the world’s tropical and subtropical seas, except the Mediterranean. They often form large, size specific schools, frequently associated with dolphins or floating objects. Yellowfin is a large fast growing species, reaching maximum sizes of 240cm in length, 200kg in weight and an age of 8 years. They mature when 2 to 5 years old and mainly spawn in summer. Smaller fish are mainly limited to surface waters, while larger fish are found in surface and deeper waters, but rarely below 250m. Yellowfin has medium resilience to fishing.

Stock information

Criterion score: 0 info

Stock Area

Australia and Fiji

Stock information

The yellowfin tuna fishery in the Western and Central Pacific Ocean (WCPO) is the second largest after skipjack, and is assessed and managed by the Western and Central Pacific Fisheries Commission (WCPFC).

A new stock assessment was carried out in 2017 and is similar to that from 2014, now including data up to the end of 2015. There is a 96% probability that overfishing is not occurring (F at 0.74Fmsy) and the stock is not considered to be in an overfished state (92% probability), with spawning biomass levels (SB) 33% of unfished levels and median spawning biomass levels, SB, at 1.39SBMSY. Maximum Sustainable Yield (MSY) has been revised upwards in the new assessment to 670,800 t (it was 586,400t in 2014).

Total yellowfin catch in the WCPO has slowly increased over time but jumped to a new level in 1998, with annual catches regularly exceeding 500,000t ever since. The stock has been continuously declining for about 50 years, since the late 1960’s. Levels of fishing mortality and depletion differ between regions, and fishery impact is highest in the tropical region, mainly due to the purse seine fisheries in the equatorial Pacific and the “other” fisheries within the Western Pacific. Both juvenile and adult fishing mortality show a steady increase since the 1970s, but while juvenile fishing mortality has stabilized since the late 1990s, adult fishing mortality has increased continuously. The scientific committee continues to recommend measures to reduce fishing mortality on juveniles and maintain current spawning biomass levels.

The yellowfin catch for 2016 (650,491 t) was the highest recorded (more than 40,000 t higher than the previous record catch of 2008 - 609,458 t); the increase in yellowfin tuna catch from 2015 levels was mainly due to increased catches in the purse seine fishery and the Indonesia and Philippines domestic fisheries.

Management

Criterion score: 0.5 info

Most tuna stocks range across and are accessed by numerous coastal states, making harmonised and effective management of these individual stocks very difficult. As a result, intergovernmental Regional Fisheries Management Organisations (RFMOs) have been established. There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. The tuna fisheries in the Western and Central Pacific Ocean (WCPO) are managed by the Western and Central Pacific Fisheries Commission (WCPFC). Whilst the RFMOs are responsible for the development of management and conservation measures, the degree to which they are implemented, monitored and enforced still varies significantly between coastal states. For this reason, it is important to choose tuna that has been caught by vessels that are well regulated by their flag state.

WCPFC has put in place a lower limit for the spawning biomass of bigeye, skipjack, and yellowfin tuna of 20 percent of unfished levels (SB/SBF=0, aka spawning biomass depletion ratio), below which the stock should not fall. For skipjack there is also an interim target of 50 percent of unfished levels, which was adopted in 2015 and has been reached. The scientific committee recommends reducing fishing mortality on juvenile bigeye and yellowfin in the tropics, through preventing increases in overall fishing mortality, until targets for these two stocks can be agreed. The commission is looking to establish harvest strategies for key fisheries and stocks but has not yet completed this work and so, as of January 2018, a bridging measure is in force to manage bigeye, yellowfin and skipjack - the measure lasts until harvest strategies are in place or until February 2021. As part of this, spawning biomass depletion ratios for bigeye and yellowfin are to be maintained at recent levels (the average from 2012-2015) and skipjack at 50 percent. The bridging measure includes a number of new measures and consolidates some pre-existing ones, and is outlined below.

In the tropical region, between 20 degrees North and 20 degrees South, the following applies:
The use and deployment of FADs is prohibited for 5 months of the year (3 months for Kiribati and the Philippines). VMS polling frequency increases to every 30 minutes during the FAD closure.
Effort limits (in vessel days) apply to purse seining on the high seas (excluding Small Island Developing States, SIDS): limits vary by country. In order not to undermine the effectiveness of this, countries cannot transfer effort into areas outside of this region.
To create an incentive to reduce the non-intentional capture of juvenile fish, to discourage waste and to encourage an efficient utilization of fishery resources, purse seiners must retain on board and then land or transship at port all bigeye, skipjack, and yellowfin tuna (also applies to national waters).
All purse seine vessels operating on the high seas or within national waters in this region must carry an observer. This also applies to purse seiners anywhere in the convention area fishing in waters under multiple countries’ jurisdiction or moving between the high seas and national waters.
The number and capacity of large (over 24m) purse seiners and longliners (with freezing capacity and ice-chilled) operating in this area is frozen to 2016 levels (excluding SIDs and Indonesia).

Other measures that apply to the wider convention area:
The number of drifting FADs with activated instrumented buoys deployed at any one time is limited to 350 per purse seine vessel.
Catch and/or effort limits apply for purse seining within national waters (both the type of limit and the amount vary by country).
There are country-specific limits on longline bigeye catch, and by 2020 hard limits for bigeye and a framework to allocate them amongst countries shall be developed.
Catches by other commercial tuna fisheries for bigeye, yellowfin or skipjack tuna (excluding those taking less than 2,000 tonnes) shall not exceed either the average level for the period 2001-2004 or the level of 2004.

More generally:
There is a requirement to submit FAD management plans, including information on strategies used to implement closures and other measures for reducing mortality of juvenile bigeye. A number of aspects in the bridging measure have been brought forward from previous management measures, and it isn’t clear how well they have been implemented, especially given the ongoing increases in total catch of skipjack. The scientific committee recommends more comprehensive data collection relating to FADs.
Observer coverage on purse seiners is poor in areas not specified in the bridging measure and only 5% coverage is required on longliners greater than 20m in length. 20% is considered to be the minimum to be effective.
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.

Capture Information

Criterion score: 0.5 info

Since the late 1990s, the purse seine catch of yellowfin tuna has accounted for about 3-5 times the longline yellowfin catch. In 2016, longlining accounted for about 15% of the total catch. Pelagic longlining in the WCPO is associated with the incidental capture and mortality of vulnerable species including sharks, turtles, sea birds and billfish.

These particular fleets are certified sustainable by the Marine Stewardship Council (MSC) and so are subject to greater monitoring and reporting requirements and need to be able demonstrate implementation of various mitigation and monitoring measures in order to maintain their certification.

There is concern that some seabird species, notably albatrosses and petrels, are threatened with global extinction. Of critical concern is Antipodean wandering albatross, which is expanding foraging range into tuna fishery areas and has experienced a high and sustained rate of decline - it is now in New Zealand’s “Nationally Critical” conservation status category. High bycatch of seabirds, especially albatross, continue to be reported by some countries fishing south of 30 degrees South. The Commission for the Conservation of Antarctic Marine Living Resources advises that, together with illegal, unreported and unregulated fishing, the greatest threat to Southern Ocean seabirds is mortality in longline fisheries in waters adjacent to its Convention Area. Countries are expected to implement the International Plan of Action for Reducing Incidental Catches of Seabirds in Longline Fisheries (IPOA-Seabirds) and report back on this. South of 30 degrees South and north of 23 degrees North, longliners must use at least 2 mitigation measures. In the area between, longliners need only use 1. The simultaneous use of 3 measures (weighted branch lines, bird scaring lines and night setting) remains the best practice approach. Further research is being done on hook shielding devices, and countries are encouraged to develop and refine measures to mitigate seabird bycatch, including safe release of seabirds captured alive. Scientific advice is to review observer coverage rates (used to estimate total seabird interactions), which is not currently being done.

The five marine turtle species in the WCPFC Convention Area are threatened or critically endangered, and WCPFC does not hold sufficient information to quantify the severity of the threat posed by longline fisheries to sea turtle populations. Measures to mitigate turtle bycatch, from 2008, are: to safely recover and release captured turtles, for purse seiners to avoid encircling them, for longliners to carry cutters and dehookers for releasing them, and for shallow-set swordfish longliners to use circle hooks and whole finfish bait (some exemptions to the latter measure apply, e.g. if there is 10% observer coverage). Under this measure, less than 1% of Western and Central Pacific Ocean (WCPO) longline effort is subject to mitigation, even though approximately 20% of the WCPO longline effort consists of shallow sets. To improve current management measures, research into turtle bycatch mitigation is ongoing. Research includes, but is not limited to, the wider use in longline fisheries of large circle hooks and/or whole finfish for bait. Improvements in data collection on interactions with sea turtles are needed. Although interaction rates are higher in shallow-set longlines, mitigation for deep-set longlines would deliver greater reductions in total interactions because effort in deep-set longline fisheries is 4 times that of shallow sets. Similarly, introducing mitigation to deep-set longlines would deliver greater reductions in at-vessel mortality compared to shallow-sets, because sea turtles have a higher probability of asphyxiation in deep sets.

In 2016, catches of silky sharks in the longline fishery were around three times higher than in the purse seine fishery. Shark measures include: full utilisation of permissible sharks and retention of no more than 5% of fins to total shark weight, a prohibition to land silky and oceanic whitetip sharks, and a prohibition on the use of shark lines. The effectiveness of these measures are difficult to evaluate owing to lack of data. As of 2014, shark management plans are required where sharks are being targeted, although to date only 2 countries have developed them. There are measures to improve recording of manta and mobula rays discarded and released, and to treat these species as key shark species for assessment and research. In 2017 the scientific committee recommended guidelines for safe release of manta and mobulid rays, which were adopted by the WCPFC. The commission is also looking to develop guidelines for other rays and sharks, especially silky shark and oceanic whitetips, as well as develop stronger and more comprehensive management measures for sharks, but there is no stated deadline for this. It is recommended that target and limit reference points are established for pelagic sharks.

In general, the effectiveness of the above measures has not been evaluated. Monitoring is deficient and the reporting of interactions with vulnerable species is poor. The scientific committee has recommended a continuation of the work on purse seine bycatch estimates and extension of this work to producing estimates of bycatch in the longline fisheries for 2018, acknowledging the issues related to the 5% observer coverage in these fisheries.

References

MSC, 2017. Marine Stewardship Council: Fiji albacore tuna longline. Available at https://fisheries.msc.org/en/fisheries/fiji-albacore-tuna-longline [Accessed on 20.11.2017].

MSC, 2017. Marine Stewardship Council: Walker Seafood Australian albacore, yellowfin tuna, and swordfish longline. Available at https://fisheries.msc.org/en/fisheries/walker-seafood-australian-albacore-yellowfin-tuna-and-swordfish-longline [Accessed on 20.11.2017].

WCPFC, 2017. Provisional outcomes document, WCPFC14-2017-outcomes, from the Western & Central Pacific Fisheries Commission Fourteenth Regular Session (As at 18 December 2017), 3-7 December 2017, Manila, Philippines. 15 pp. Available at https://www.wcpfc.int/meetings/wcpfc14 {Accessed on 18.12.2017]

WCPFC, 2017. Summary Report of the Thirteenth Regular Session of the Scientific Committee of the Commission for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean, 9 - 17 August 2017, Rarotonga, Cook Islands. 281 pp. Available at https://www.wcpfc.int/meetings/sc13 [Accessed on 27.11.2017]