Tuna, yellowfin

Thunnus albacares

Method of production — Caught at sea
Capture method — Purse seine (FAD & Free School)
Capture area — Indian Ocean: Western (FAO 51), Eastern ( FAO 57)
Stock area — Indian Ocean
Stock detail — All Areas
Picture of Tuna, yellowfin

Sustainability rating five info

Sustainability overview

Updated: November 2020

Yellowfin tuna in the Indian Ocean is in an overfished state, and subject to overfishing. Recent catches have been above the catch limits and this lack of compliance by the fishery is concerning. If catches continue to increase it could lead to the stock crashing by 2027. There are significant issues with monitoring and compliance in most fisheries that are overseen by the Indian Ocean Tuna Commission (IOTC). This reduces the accuracy of stock assessments, the effectiveness of management measures, and the likelihood of maintaining the fisheries at a sustainable level. Observer coverage, which could improve monitoring, is very low, at just 5%. Recommendations are for 20%. Therefore, MCS considers Indian Ocean tuna and swordfish fisheries to be poorly managed and requiring considerable improvement. On average from 2015-2019, purse seine fishing accounted for around 35% of yellowfin tuna catches. Most, around 23%, used Fish Aggregating Devices (FADs). Purse seining is associated with bycatch of species such as sharks, turtles and marine mammals, although less so than longlining. Whilst bycatch may comprise a small proportion of the total catch, the high volume of tuna that is caught means that it can still be significant for these vulnerable species. Bycatch is higher where Fish Aggregation Devices are being used. Poorly-designed FADs can entangle vulnerable species, and can also become lost at sea, continuing to ghost fish and be a source of marine debris. The IOTC is reducing the number of FADs that countries can use, and working on ways to reduce the impacts through development of biodegradable and non-entangling FADs, but concerns remain.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to reduce impacts to and improve reporting of interactions with vulnerable species and to recover the yellowfin stock. Large buyers should consider supporting such improvements.

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: 0.75 info

Indian Ocean yellowfin tuna has been overfished and subject to overfishing since 2015, and recent catches have been some way above recommended limits.

This stock is managed by the Indian Ocean Tuna Commission (IOTC). Catches of Indian Ocean yellowfin tuna peaked in 2004 at over 500,000 t, dropped to around 250,000 t in 2009 and in recent years have stabilised at around 400,000 t. A stock assessment was carried out in 2018, indicating that the stock was overfished and subject to overfishing. Spawning Biomass, SB, was estimated to be at 83% of levels associated with Maximum Sustainable Yield (0.83 SBMSY). Fishing mortality, F, was at 120% of levels associated with MSY (1.2 FMSY). There is some uncertainty in these estimates and a workplan is underway to address these uncertainties, although no new advice could be provided in 2019. Discussions were not progressed in 2020, owing to Covid disruption, but a special meeting is scheduled for March 2021 to plan a new stock assessment and improve management.

Provisional catch in 2019 was 427,240 tonnes, taking the 2015-2019 average catch to 424,103t. This is higher than the estimated Maximum Sustainable Yield, which is 403,000t. Projections indicated that if catches were maintained at 410,000t there would be a 90-94% probability of the stock exceeding its limits by 2027, meaning that SSB would be less than 0.4 SSBMSY and F would be above 1.4 FMSY. If catches were maintained at 450,000t, it is projected by 2027, the stock would either crash, or at least one fishery wouldn’t be able to take its catch due to absence of fish. Reductions in catch to around 327,000 t would be needed to see the stock recovering to sustainable levels by 2027 with 50% probability.

The stock status has been driven by unsustainable catches of yellowfin tuna taken over the last five years, and the relatively low recruitment levels in recent years.

It is possible that the stock area does not match management areas, as the boundary between the Atlantic Ocean and Indian Ocean stock is not clear, but genetic analysis suggests that more of the South African catch is from the Indian Ocean stock, while it is currently reported as Atlantic stock.

Management

Criterion score: 0.75 info

Yellowfin tuna in the Indian Ocean is in an overfished state, and subject to overfishing. Recent catches have been above the catch limits and this lack of compliance by the fishery is concerning. If catches continue to increase it could lead to the stock crashing by 2027. There are significant issues with monitoring and compliance in most fisheries that are overseen by the Indian Ocean Tuna Commission (IOTC). This reduces the accuracy of stock assessments, the effectiveness of management measures, and the likelihood of maintaining the fisheries at a sustainable level. Observer coverage, which could improve monitoring, is very low, at just 5%. Recommendations are for 20%. Therefore, MCS considers Indian Ocean tuna and swordfish fisheries to be poorly managed and requiring considerable improvement.

Most tuna stocks range across and are accessed by numerous coastal states, making harmonised and effective management of these individual stocks very difficult. To try and achieve this, Intergovernmental Regional Fisheries Management Organisations (RFMOs) have been established; for this stock it is the Indian Ocean Tuna Commission (IOTC). There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. 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.

Monitoring and compliance with management measures in the IOTC region is generally poor, and MCS is particularly concerned about the impact this is having on a number of species. Some countries repeatedly fail to report catch data to the commission annually. In 2018 IOTC introduced a new measure aimed at improving reporting on catch and bycatch, including prohibiting a country from retaining a species if they fail to report catches for it. However, in 2020 the scientific committee reported that data reporting issues persist.

The 2018 stock assessment indicated that the yellowfin stock remains overfished and subject to overfishing, and the scientific committee continues to recommend that catches should be reduced by 20% from to 2014 levels to around 330,000 tonnes. A yellowfin tuna rebuilding plan has been in place since 2016, mainly focussed on reducing catches. Countries whose 2014 catches exceeded certain thresholds (5000t for all gears except gillnet, which is 2000t) should reduce their catches by a certain amount compared to 2014 levels (purse seine by 15%, gillnet and longline by 10%, other gears by 5%). Countries can determine their own methods for achieving these reductions. If they exceed their catch limits, the excess is deducted from the following two years’ allowance. In addition, the number of supply vessels (which increase fishing capacity) is limited to 50% of the number of purse seine vessels in 2018-2019 and 40% in 2020-2022. The plan also ‘encourages’ countries to fast-track phasing out of gillnets, to set them at 2m deep to mitigate ecological impacts, and increase observer coverage on gillnetters to 10%. It is generally considered to be ineffective, as the measures are estimated to achieve only a 10% reduction from 2014 levels, and some countries may have inaccurately reported their 2014 catches as being below certain thresholds to escape the measures. Some countries, particularly the longline fleets, have achieved the required decreases, which is to be applauded. The Maldives, which are heavily dependent on healthy tuna stocks, decommissioned their longline yellowfin tuna fleet in 2019 (which was catching roughly 3,000 tons per year), to contribute rebuilding of Indian Ocean yellowfin tuna stocks. However, these efforts have been offset by significant increases elsewhere, especially in the gillnet fleets. Overall catches have increased by 7% from 2014 levels and are now 30% above the recommended limit of 330,000t. Provisional catch in 2019 was 427,240 tonnes, taking the 2015-2019 average catch to 424,103t. There is a 100% probability of the stock falling below safe limits by 2027, and it could crash, if fishing pressure is not adequately reduced. The scientific committee has also suggested that the rebuilding plan has displaced activity onto purse seines with fish aggregating devices, which has led to an associated increase in catches of skipjack tuna and juvenile yellowfin and bigeye.

MCS is very concerned by this lack of control and enforcement, which undermines the ability of the IOTC to keep the stock at sustainable levels. Over the years, widespread concern has been expressed about the state of the stock and lack of progress to rebuild it. A number of major UK supermarkets and seafood suppliers have written to the IOTC to raise concerns, and in 2020 some made commitments to stop sourcing it unless improvements were made at the IOTC meeting at the end of the year. Owing to Covid disruption, the 2020 IOTC meeting was shortened and did not discuss yellowfin tuna. Instead, a special session to discuss this stock is planned for March 2021. While catch reductions are crucial, particular focus should be on reducing catches of juvenile yellowfin. Some gears, such as purse seining on FADs, have a higher proportion of juveniles and may need further restrictions. The Iranian gillnet fishery in the Sea of Oman, responsible for around 40,000t and increasing, is almost exclusively taking juveniles. It is also crucial to improve monitoring and compliance with management measures. Any rebuilding or management plan appears highly unlikely to rebuild this stock without significant changes to ensure that catch limits are being complied with.

Additional management measures for yellowfin include:
On average from 2015-2019, purse seining accounted for around 35% of skipjack catches: 23% using Fish Aggregating Devices (FADs) and 10% on free-schooling fish. The maximum number of drifting FADs that can be in use at any one time by each purse seiner has been steadily reduced from 550 in 2015 to 300 in 2019, and the maximum that can be acquired each year reduced from 1100 in 2015, to 500 in 2019. Countries that use FADs must report regularly to the Commission and submit FAD management plans outlining how they will minimise mortality of juvenile yellowfin and bigeye tuna and vulnerable non-target species such as sharks, turtles and rays.

Vessel capacity and tonnage was frozen to 2007 levels for vessels over 24m, or vessels under this length operating in international waters. This measure expired in 2018, and IOTC reverted to previous legislation which froze capacity and tonnage to 2003 levels. This legislation is very generic, applying across all fleets, and would be better replaced by spatial and temporal closures and quota allocation. There also appear to be concerns that the freeze has not been well enforced thus far.

In 2016 IOTC introduced a number of resolutions to improve the poor compliance with existing management measures, e.g. observer coverage, catch and effort reporting, support for countries to implement measures. However, mandatory observer coverage is very low, at just 5% for all vessels over 24m or under 24m and fishing outside of their Exclusive Economic Zone (EEZ). A number of countries fail to meet the 5% threshold. In general, 20% is scientifically recommended to ensure adequate monitoring of catch and bycatch. In 2019 a proposal was put forward to increase coverage to at least 20%, but consensus could not be reached.

Other IOTC conservation and management measures of note include:
A ban on the discarding of bigeye, yellowfin and skipjack tunas by purse seine vessels which from 2018 will extend to non-target species such as other tunas and billfish.
A ban on the use of aircraft and unmanned aerial vehicles as fishing aids, which significantly contribute to fishing effort by helping to detect fish.
A ban on surface or submerged artificial lights for the purpose of aggregating tuna and tuna-like species beyond territorial waters.
In 2012 IOTC banned the use of driftnets on the high seas. In 2022 this will be extended to the entire IOTC area (i.e. within countries’ EEZs as well).
To help address IUU, the IOTC maintains an active vessel register and an IUU Vessel List and prohibits transhipments for large scale vessels at sea unless they are pre-approved, monitored by an observer and the vessel uses a Vessel Monitoring System (VMS).

Capture Information

Criterion score: 0.75 info

On average from 2015-2019, purse seine fishing accounted for around 35% of yellowfin tuna catches. Most, around 23%, used Fish Aggregating Devices (FADs). Purse seining is associated with bycatch of species such as sharks, turtles and marine mammals, although less so than longlining. Whilst bycatch may comprise a small proportion of the total catch, the high volume of tuna that is caught means that it can still be significant for these vulnerable species. Bycatch is higher where Fish Aggregation Devices are being used. Poorly-designed FADs can entangle vulnerable species, and can also become lost at sea, continuing to ghost fish and be a source of marine debris. The IOTC is reducing the number of FADs that countries can use, and working on ways to reduce the impacts through development of biodegradable and non-entangling FADs, but concerns remain. Mandatory observer coverage is very low, at just 5% for all vessels over 24m or under 24m and fishing outside of their Exclusive Economic Zone (EEZ). A number of countries fail to meet the 5% threshold. In general, 20% is scientifically recommended to ensure adequate monitoring of catch and bycatch.

Purse seines are associated with lower mortality rates of sharks, turtles and certainly birds, than longlining, however their widespread use means they may still have a significant impact on turtles, sharks and dolphins. FADs include a wide range of floating objects, from specifically made rafts to floating logs and even boats, which pelagic species aggregate around for protection and shade. Such devices have become a very efficient means of catching tunas; however they also attract a diverse range of marine life, including juvenile fish and vulnerable species. As a result, FAD-associated purse seine sets catch a higher proportion of these species compared with sets on free schooling tuna. Poorly designed FADs may also entangle animals. The increasing use of FADs is of concern due to the unknown impacts such gear might have on natural migratory patterns, growth rates and predation rates of affected pelagic species. Research into this should be prioritised. The IOTC has gradually reduced the number of drifting FADs (dFADs) allowed at any one time over the past few years (see Management tab), and countries must submit FAD management plans outlining how they will minimise mortality of juvenile yellowfin and bigeye tuna and vulnerable non-target species such as sharks, turtles and rays. To reduce the entanglement of sharks, marine turtles or any other species, the design and deployment of FADs must be based on certain principles: The surface of the FAD should not be covered, or only covered with non-meshed material; If a sub-surface component is used, it should not be made from netting but from non-meshed materials such as ropes or canvas sheets; To reduce the amount of synthetic marine debris, the use of natural or biodegradable materials should be promoted.

Sharks and rays: Better data reporting is needed, as impacts and population trends are not well understood. Piracy displaced longlining into the southern and eastern Indian Ocean, and there could be localised depletion of sharks here. Full utilisation of sharks is required (i.e. no fin removal), unwanted sharks must be released live wherever possible and shark catches must be reported annually. Countries must develop conservation and management measures for vulnerable shark species. Transshipment of oceanic whitetips and threshers is prohibited. A number of countries are banning the retention of oceanic whitetip, in accordance with IOTC resolutions, but it is too early to evaluate the impact of this. In 2019 the first resolution for any ray species in the IOTC area of competence was brought in. It protects mobulid rays, which are declining across the Indian Ocean. Targeted fishing, retention, transhipping, landing, selling, or storage of mobulid rays is prohibited, with exceptions made for accidental catch by artisanal fishing until 2022. The status of shark species in 2020 were:
Blue shark is not currently overfished or subject to overfishing, but will become so if current catches continue. It is fairly resilient, for a shark species, and is targeted by longliners in several areas as well as bycaught by swordfish longliners. Management measures could be introduced in 2021.
Oceanic whitetip is Critically Endangered, and mainly caught by trolling and gillnetting. There is not enough data to assess the stock but it could be declining.
Scalloped hammerhead is endangered in the western Indian Ocean, caught by a range of gears. It is less susceptible to being caught by longline than other sharks.
Shortfin mako is endangered and considered the most vulnerable Indian Ocean shark species as it is very susceptible to longlining, less so to purse seining. Trends are conflicting, but as it has been placed on CITES Appendix II, future landings could be affected.
Silky shark is Vulnerable, and highly susceptible to longline and purse seine. Abundance could be declining.
Bigeye thresher is Vulnerable and commonly caught as bycatch by longliners. Catches haven’t been reported since 2012. Pelagic thresher is Endangered, and highly susceptible to purse seining. It is commonly caught as bycatch by longliners. Most threshers die after being hooked, even if released. Therefore the ban on retaining them, and promoting live-release, is probably not effective at protecting them.

Turtles: The status of all turtle species in the Indian Ocean is concerning, and interactions are severely underreported. The last specific regulations to protect turtles were passed in 2012. Turtles must be released wherever possible and countries are requested to research other mitigation techniques. Longliners must carry cutters or de-hookers to aid with this but gear modification, such as circle hooks, is not required. Gillnetting is the biggest concern for turtles, with estimates ranging from 11,000-52,000 individuals being caught annually. Longlining in the southwest may also have an impact on population levels. Turtles can also be entangled by Fish Aggregating Devices used by purse seiners. Estimates of catch by longline and purse seine ranges from 250-3,500 individuals. Green turtles are mostly caught by gillnets, while loggerhead, hawksbill, leatherback and olive ridley are caught by various gears depending on the season. The scientific committee advises that maintaining or increasing fishing effort in the Indian Ocean without appropriate measures in place will likely result in further population declines. It recommends that appropriate mechanisms are developed to ensure compliance with data collection and reporting requirements.

Marine mammals: Very little effort has gone into monitoring and mitigating the bycatch and entanglement of cetaceans. Most recorded interactions are from gillnets. Longline is also of concern as cetaceans could be attracted by the fish caught on the line. Purse seine can encircle or entangle the animals, although interactions are thought to be low. It is illegal to intentionally set a purse seine net around a cetacean if the animal is sighted prior to the commencement of the set. In 2020, it was noted that there are tuna-dolphin associations for yellowfin tuna. This is where fishers wait for dolphins to encircle a school of tuna, and then try to catch the tuna, e.g. with nets. The dolphins are not targeted, but can be caught as bycatch. This association appears to be rather widespread around the Indian Ocean, and is used by coastal country fishermen in Maldives, Sri Lanka, Oman and elsewhere to target yellowfin tuna.

Several countries have failed to implement national plans of action (NPOAs) for sharks, seabirds and turtles as required (although the shark plan is not binding in India as they have objected to the measure). In 2020, of the 34 members of IOTC, 16 countries had completed NPOAs for sharks. Just 7 had plans for seabirds, although 8 countries report low or no interaction because they don’t use longline or don’t fish south of 25 degrees S. 11 countries had plans for turtles. Click here to see which countries had and had not fully implemented NPOAs.

Mandatory observer coverage is very low, at just 5% for all vessels over 24m or under 24m and fishing outside of their Exclusive Economic Zone (EEZ). A number of countries fail to meet the 5% threshold. In general, 20% is scientifically recommended to ensure adequate monitoring of catch and bycatch. In 2019 a proposal was put forward to increase coverage to at least 20%, but consensus could not be reached.

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].

Aranda, M., 2017. Description of tuna gillnet capacity and bycatch in the IOTC Convention Area, IOTC-2017-WPEB13-18, for the 13th Working Party on Ecosystems and Bycatch for the Indian Ocean Tuna Commission, 4-8 September 2017, San Sebastian, Spain. 28pp. Available at http://www.iotc.org/meetings/13th-working-party-ecosystems-and-bycatch-wpeb13 [Accessed 23.11.2017].

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].

Eighani, M., Naderi, R. A. and Cope, J., 2020. Understanding fishery interactions and stock trajectory of yellowfin tuna exploited by Iranian fisheries in the Sea of Oman. IOTC-2020-WPTT22(AS)-20. Presented to 22nd IOTC Working Party on Tropical Tunas (WPTT22): Stock Assessment Meeting, 19-23 October 2020, Online. Available at https://iotc.org/documents/WPTT/2202/20 [Accessed on 08.12.2020].

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IOTC, 2018. Report of the 22nd Session of the Indian Ocean Tuna Commission, IOTC-2018-S22-R[E]. 21-25 May 2018, Bangkok, Thailand, 144pp. Available at https://iotc.org/documents/report-22nd-session-indian-ocean-tuna-commission [Accessed on 28.11.2019].

IOTC, 2019. Report for the 23rd session of the Indian Ocean Tuna Commission, IOTC-2019-S23-R_rev1[E], 17-21 June 2019, Hyderabad, India. Available at https://iotc.org/sites/default/files/documents/2019/10/IOTC-2019-S23-RE_Rev1_FINAL.pdf [Accessed on 26.11.2019].

IOTC, 2019. On a regional observer scheme. Paper IOTC-2019-S23-PropJ[E] submitted by the European Union to the 23rd session of the Indian Ocean Tuna Commission, 17-21 June 2019, Hyderabad, India. 5pp. Available at https://iotc.org/documents/regional-observer-scheme-eu [Accessed on 27.11.2019].

IOTC, 2019. Compendium of Active Conservation and Management Measures for the Indian Ocean Tuna Commission, 29 October 2019. Available at https://iotc.org/sites/default/files/documents/compliance/cmm/IOTC_-_Compendium_of_ACTIVE_CMMs_29_October_2019_designed.pdf [Accessed on 04.12.2020].

IOTC, 2020. Draft resource stock status summary - yellowfin tuna: (YFT: Thunnus albacares). IOTC-2020-SC23-ES04. Available at https://iotc.org/documents/yellowfin-tuna-0 [Accessed on 07.12.2020].

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IOTC, 2019. Status of development and implementation of national plans of action for seabirds and sharks, and implementation of the FAO guidelines to reduce marine turtle mortality in fishing operations. IOTC-2020-SC23-06_rev1[E]. 13pp. Available at https://iotc.org/documents/SC/23/06E [Accessed on 04.12.2019].

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