Tuna, yellowfin

Thunnus albacares

Method of production — Caught at sea
Capture method — Pole & line; Handline
Capture area — Pacific, North West (FAO 61) and Central (FAO 71,77)
Stock area — Western and Central Pacific
Stock detail — All Areas
Picture of Tuna, yellowfin

Sustainability rating two info

Sustainability overview

Updated: November 2020

The Western and Central Pacific Ocean (WCPO) yellowfin stock supports the second largest tuna fishery in the world. It is not overfished nor subject to overfishing. A Harvest Control Rule is yet to be developed for yellowfin. Until then, management measures are mainly aimed at limiting fishing effort by purse seiners, which is responsible for around 55% of the yellowfin catch. Observers, to verify catch and bycatch, are on 100% of purse seiners within the main fishing grounds, but are low for other areas and gear types at just 5%. There is not enough data to be sure that countries are complying with the management measures. Around 6% of the WCPO yellowfin catch is from pole and line fisheries. This method of fishing targets fish near the surface, and so rarely touches the seabed and doesn’t have habitat impacts. It is labour-intensive and very selective, meaning there are low levels of bycatch of vulnerable species. Pole and line fishing can use large quantities of live fish for bait, which could have impacts on baitfish populations.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to improve monitoring and reporting of catches and encourage some management of bait fish fisheries. Large buyers should consider supporting such improvements.

There are a number of Fishery Improvement Projects to improve handline and pole & line fisheries in the tropical Western and Central Pacific. More info about these FIPs is available from fisheryprogress.org.

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

The yellowfin tuna fishery in the Western and Central Pacific Ocean (WCPO) is the second largest in the world after skipjack. It is not overfished and not subject to overfishing.

This stock is assessed and managed by the Western and Central Pacific Fisheries Commission (WCPFC). A new stock assessment was carried out in 2020 using data up to 2018. Fishing for this stock began in the 1950s and catches have steadily increased to peak in 2017 at around 700,000 tonnes. During this time, Fishing Mortality (F) increased until the early 2000s, when it stabilised for juveniles but carried on increasing for adults. The average F from 2014-2017 was 36% of levels associated with Maximum Sustainable Yield (MSY) (F2014-2017 / FMSY = 0.36). Meanwhile, Spawning Biomass (SB) continuously declined to around 50% of unfished levels in the mid-2000s, and has stayed relatively stable since then. In the latest stock assessment it is at 58% (SB2015-2018 / SBF=0 = 0.58). A limit Reference Point has been set for this stock of 20%. Below this level, the stock would be considered depleted. All models in the assessment indicated that the stock was above the LRP, and fishing mortality rates below FMSY, with 100% probability. Based on the results of this assessment, the yellowfin stock in the WCPO is not considered overfished, nor subject to overfishing. Preliminary catch in 2019 was 669,362t, a 5% decrease from 2018 and a 1% increase from the average 2014-2018.

Recruitment levels have declined over time as the stock size has declined, but have stabilized over the last 20 years and recently slightly increased. Overall, there has been a decline in the proportion of old (greater than age class 15) fish in the population since the 1970s. 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. The scientific committee continues to recommend measures to reduce fishing mortality on juveniles and maintain current spawning biomass levels.

The 2020 assessment is more optimistic than the 2017 assessment, but the causes aren’t clear. MSY in the 2020 assessment (1,000,000 tonnes) is 63% higher than in 2017. There are some research needs to improve the assessment, including estimation of natural mortality rates using tagging data.

Management

Criterion score: 0.5 info

The Western and Central Pacific Ocean (WCPO) yellowfin stock supports the second largest tuna fishery in the world. It is not overfished nor subject to overfishing. A Harvest Control Rule is yet to be developed for yellowfin. Until then, management measures are mainly aimed at limiting fishing effort by purse seiners, which is responsible for around 55% of the yellowfin catch. Observers, to verify catch and bycatch, are on 100% of purse seiners within the main fishing grounds, but are low for other areas and gear types at just 5%. There is not enough data to be sure that countries are complying with the management measures.

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. A significant proportion of West Pacific skipjack and yellowfin tuna is caught within the waters of the Parties to the Nauru Agreement (PNA). These South Pacific island nations have incorporated additional management measures, and pushed for improvements in the wider management of these stocks. In addition, around 50% of West Pacific purse-seine-caught skipjack and 70% of yellowfin is certified by the Marine Stewardship Council. There are also several fishery improvement projects for WCPO yellowfin, some of which are making improvements to management and fishing practices and seeing results on the water.

WCPFC is looking to establish harvest strategies for key fisheries and stocks but has not yet completed this work and so a bridging measure is in force to manage bigeye, yellowfin and skipjack. It lasts from 2018 until harvest strategies are in place, or February 2021. There is a limit reference point for the spawning biomass of bigeye, skipjack, and yellowfin tuna of 20% of unfished levels (SB/SBF0 = 0.2), below which the stock should not fall. Skipjack also has an interim target reference point of 50% of unfished levels, while bigeye and yellowfin are to be maintained at recent levels (the average from 2012-2015). Yellowfin stock has stayed fairly stable since 2010 and is currently above the limit reference point, at 58%. It is not overfished, nor subject to overfishing. However, the scientific committee recommends caution on interpreting this for management decisions. It recommends that fishing mortality on yellowfin tuna should not be increased from the level that maintains spawning biomass at 2012-2015 levels until the Commission can agree on an appropriate target reference point. It also notes that further increases in yellowfin fishing mortality would likely affect other stocks and species which are currently moderately exploited due to the interactions in WCPFC fisheries.

An evaluation of the bridging measure in 2019 found that it would achieve its targets if bigeye recruitment remains high, but if that declines, fishing mortality will double to above FMSY and biomass has a 20% chance of dropping below the limit reference point. For yellowfin, the measure will marginally fail its aims as SB will experience a small decrease. The bridging measure includes a number of new measures and consolidates some pre-existing ones. 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. It also recommends reducing fishing mortality on juveniles by preventing increases in overall fishing mortality. In the tropical region, between 20 degrees North and 20 degrees South, the following applies:
FADs are banned 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. Effort shouldn’t be transferred into areas outside of the bridging measure. Large purse seine and longline vessel numbers and capacity are frozen to 2016 levels (excluding SIDs and Indonesia).
Purse seiners must retain and land all bigeye, skipjack, and yellowfin tuna. This is intended to incentivise reductions in bycatch of juvenile fish.
100% observer coverage is required for purse seine vessels. Outside of the areas covered by the bridging measure, observer coverage on purse seiners is poor. Only 5% coverage is required on longliners greater than 20m in length. 20% is considered to be the minimum to be effective.

Other measures that apply to tuna in the wider convention area:
Each purse seine vessel is limited to 350 drifting FADs at a time. Countries should have FAD management plans, with strategies to implement closures and other measures for reducing mortality of juvenile bigeye.
Catch and/or effort limits apply to purse seining within national waters (it varies by country). For bigeye, there are country-specific limits on longline catch. By 2020, limits for bigeye and a framework to allocate them amongst countries should be developed. Catches by other fisheries for bigeye, yellowfin or skipjack tuna (except those taking less than 2,000 tonnes) are frozen to either the average level for 2001-2004 or the level of 2004.

More generally:
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.

The Parties to the Narau Agreement (PNA), which covers a number of South Pacific Islands and produces 25% of the world’s tuna, has a series of agreements in place to control access to tuna it is waters and increase economic benefits for South Pacific islanders. Their IUU aerial surveillance programme in 2017 covered 100% of the EEZs in their area. 90% of FAD sets in the WCPO were in PNA waters, and FAD density is high - 400-500 FADs in one degree square (roughly 110km sq.) per month. A recent PNA report estimated that 7% of FADs ‘beach’ (with concerns for pollution and navigation safety) and up to 52% were lost (drift outside the fishing ground of the company owning it, at which point the company is likely to abandon it). Therefore, ghost fishing is of concern where FADs have entangling elements. 98% of FADs have echo-sounders, allowing remote monitoring of the biomass near them. There are plans to develop this technology to distinguish between species to enable reduction of fishing mortality on bigeye.

Capture Information

Criterion score: 0.25 info

Around 6% of the WCPO yellowfin catch is from pole and line fisheries. This method of fishing targets fish near the surface, and so rarely touches the seabed and doesn’t have habitat impacts. It is labour-intensive and very selective, meaning there are low levels of bycatch of vulnerable species. Pole and line fishing can use large quantities of live fish for bait, which could have impacts on baitfish populations.

Pole and line fishing consists of a bamboo or plastic pole, 10 to 15 feet in length, with a line and a feathered barbless hook attached to the smaller end of the pole, capable of handling a fish weighing below 23kg. It can use large quantities of live fish for bait, which could have impacts on baitfish populations.

Observer coverage in WCPFC fisheries is just 5%, which is considered to be too low for accurate data on bycatch. A minimum of 20% coverage is recommended.

References

ACAP, 2019. ACAP Review and Best Practice Advice for Reducing the Impact of Pelagic Longline Fisheries on Seabirds, Reviewed at the Eleventh Meeting of the Advisory Committee of the Agreement on the Conservation of Albatrosses and Petrels, 13 - 17 May 2019, Florianopolis, Brazil. Available at https://www.acap.aq/en/bycatch-mitigation/mitigation-advice/3498-acap-2019-review-and-best-practice-advice-for-reducing-the-impact-of-pelagic-longline-fisheries-on-seabirds/file [Accessed on 29.11.2019].

Brouwer, S., Pilling, G., Williams, P., WCPFC Secretariat , 2017. Trends in the South Pacific albacore longline and troll fisheries, Document WCPFC-SC13-2017/SA-WP-08 for 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. 70 pp. Available at https://www.wcpfc.int/meetings/sc13 [Accessed on 27.11.2017].

Dias, M. P., Martin. R., Pearmain, E., J., Burfield, I. J., Small, C., Phillips, R. A., Yates, O., Lascelles, B., Garcia Borboroglu, P. and Croxall, J. P., 2019. Threats to seabirds: A global assessment. Biol. Cons. 237, pp 525-537. https://doi.org/10.1016/j.biocon.2019.06.033 [Accessed on 29.11.2019].

IPNLF, 2012. Ensuring sustainability of live bait fish, International Pole and Line Foundation, London, 57 pp.

ISSF, IPNLF, 2019. Skippers’ Guidebook to Pole-and-Line Fishing Best Practices. Version 1.0 - April 2019. International Seafood Sustainability Foundation and International Pole & Line Foundation. Available at http://ipnlf.org/perch/resources/pl-guidebookipnlfissffinal.pdf [Accessed on 30.11.2020].

ISSF, 2020. Status of the world fisheries for tuna. Nov. 2020. ISSF Technical Report 2020-16. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2020-16-status-of-the-world-fisheries-for-tuna-november-2020/ [Accessed on 10.12.2020].

Phillip, N.B. and Escalle, L., 2020. Updated evaluation of drifting FAD construction materials in the WCPO. WCPFC-SC16-2020/EB-IP-03 presented to the Western and Central Pacific Fisheries Commission Scientific Committee 16th Regular Session, 11-20 August 2020, Online. Available at https://www.wcpfc.int/node/46724 [Accessed on 11.12.2020].

WCPFC, 2020. Summary Report of the Sixteenth Regular Session of the Scientific Committee of the WCPFC, 12-19 August 2020 (Reconvened on 10 September 2020), Online. Available at https://www.wcpfc.int/file/568072/download?token=hcPeql6u [Accessed on 10.12.2020].

WCPFC, 2020. Conservation and Management Measures of the Western and Central Pacific Fisheries Commission. Compiled 2 Nov 2020 - 09:46. Available at https://www.wcpfc.int/system/files/booklets/31/CMM%20and%20Resolutions.pdf [Accessed on 10.12.2020].

Vincent M., Ducharme-Barth, N., Hamer,P., Hampton, J., Williams, P. and Pilling, G., 2020. Stock assessment of yellowfin tuna in the western and central Pacific Ocean. WCPFC-SC16-2020/SA-WP-04 (Rev.3) presented to the Western and Central Pacific Fisheries Commission Scientific Committee 16th Regular Session, 11-20 August 2020, Online. Available at https://www.wcpfc.int/node/46611 [Accessed on 11.12.2020].