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
Updated: November 2019
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 0.83 SB MSY and fishing mortality, F at 1.2 F MSY). 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. Provisional catch in 2018 was 423,815 tonnes - an increase from 2017 (409,101t) and taking the 2014-2018 average catch to 404,655t. This is higher than the estimated Maximum Sustainable Yield, which is 403,000t. Projections indicated that if 2017 catch levels were to be maintained there would be a 100% probability of the stock exceeding its limits (SSB would be less than 0.4 SSBMSY and F would be above 1.4 FMSY) by 2027. Should catches increase by 10% to 450,000t, it is projected that the stock would crash by 2027. Reductions in catch of 20% or more (i.e. to around 327,000 t) would 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. Some countries in the IOTC do not report fishery data which is important for stock assessment and management and in 2018, the IOTC introduced a new measure aimed at improving reporting on direct and incidental catches, including prohibiting a country from retaining a species if they fail to report catches for that species.
Purse seine fishing accounts for 31% of yellowfin tuna catch: 27% using Fish Aggregating Devices (FADs) and 4% on free-schooling fish. In recent years, the proportion of the purse seine catch taken on FADs has been increasing, peaking in 2018 at 116,000t. Yellowfin is often taken in purse seine sets targeting the smaller skipjack tuna. Purse seines are associated with relatively low mortality rates of vulnerable bycatch species yet their widespread use means they can still have a significant impact on these species. FAD associated sets catch a higher proportion of these species compared with sets on free schooling tuna and poorly designed FADs may also entangle animals, although FAD management is improving. Monitoring and mitigation of vulnerable bycatch species interactions is insufficient and observer coverage is relatively low at 5% for vessels over 24m and for vessels fishing on the High Seas.
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.
There are fleets operating within this fishery that are a Fishery Improvement Project (FIP) making progress at improving elements of the fishery. Please see the FIP specific rating for more information.
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.
Criterion score: 0.75 info
Indian Ocean stocks are 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 0.83 SB MSY and fishing mortality, F at 1.2 F MSY). Spawning stock biomass in 2017 was estimated to be 30% of the unfished levels. 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.
Provisional catch in 2018 was 423,815 tonnes - an increase from 2017 (409,101t) and taking the 2014-2018 average catch to 404,655t. This is higher than the estimated Maximum Sustainable Yield, which is 403,000t. Projections indicated that if 2017 catch levels were to be maintained there would be a 100% probability of the stock exceeding its limits (SSB would be less than 0.4 SSBMSY and F would be above 1.4 FMSY) by 2027. Should catches increase by 10% to 450,000t, it is projected that the stock would crash by 2027. Reductions in catch of 20% or more (i.e. to around 327,000 t) would 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.
Criterion score: 0.75 info
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.
There are persistent failures by some countries to report to the commission annually, including reporting catch data, and other issues with lack of data and poor quality data persist. In 2018 IOTC introduced a new measure aimed at improving reporting on direct and incidental catches, including prohibiting a country from retaining a species if they fail to report catches for that species.
IOTC has set targets and thresholds for fishing effort and spawning stock biomass for the species it manages, but there is no Total Allowable Catch. The 2018 stock assessment indicates that the stock remains overfished and subject to overfishing, and that current catches remain unsustainable. There is a 100% probability of the stock falling below safe limits by 2027 if fishing pressure is not adequately reduced. In 2018 the scientific committee continued to recommend that catches should be reduced by 20% from to 2014 levels to around 330,000 tonnes. Provisional catch in 2018 was 423,815 tonnes, an increase of around 9% from 2014 levels. Work to implement a formal management procedure is underway, but not expected to be completed until 2021.
Widespread concern has been expressed about the state of the stock and lack of progress to rebuild it. Sainsbury’s, Waitrose, Marks and Spencer, Tesco, Asda, Morrison’s, Co-op, and New England Seafood International provided a joint statement to the IOTC in 2019 expressing their concern over the lack of an effective rebuilding plan and robust harvest strategy. 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.
A yellowfin tuna rebuilding plan has been in place since 2016, mainly focussed on reducing catches. In 2017, 2018 and 2019 the measures in force were estimated to achieve only a 10% reduction from 2014 levels. Some of the fisheries subject to catch reductions had fully achieved a decrease in catches in 2018 in accordance with the plan, but these reductions were offset by increases in catches from exempt countries. Some countries may have inaccurately reported their 2014 catches as being below certain thresholds so as to escape some measures.
The rebuilding plan requires countries whose 2014 catches exceeded certain thresholds (5000t for all gears except gillnet, which is 2000t) must 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%.
Other IOTC conservation and management measures of note include:
A ban on the discarding of bigeye, yellowfin and skipjack tunas by purse seine vessels, as well as of non target species such as other tunas and billfish.
A ban on the use of aircrafts 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).
Regarding the use of drifting Fish Aggregation Devices (FADs): 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.
There was a freeze on capacity and tonnage to 2006 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.
5% regional observer coverage is required for all vessels over 24m and for vessels under 24m fishing outside of their Exclusive Economic Zone (EEZ). In 2019 a proposal was put forward to increase this to at last 20%, as 5% was considered to be insufficient. However, consensus on minimum coverage could not be reached.
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).
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.
Criterion score: 0.75 info
Purse seine fishing accounts for around 31% of yellowfin tuna catch: 27% using Fish Aggregating Devices (FADs) and 4% on free-schooling fish. In recent years, the proportion of the purse seine catch taken on FADs has been increasing, peaking in 2018 at 116,000t. At the same time, purse seine catches on free schooling fish have fluctuated between 30,000t and 60,000t, dropping to just 15,000t in 2018 - an all-time low. Yellowfin is often taken in purse seine sets targeting the smaller skipjack tuna. The IOTC scientific committee has noted that the increasing proportion of juvenile yellowfin being caught, particularly in FAD purse seine fisheries targeting skipjack, has reduced the maximum sustainable yield of the yellowfin stock.
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.
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.
Regarding bycatch species:
Purse seine vessels (excluding artisanal fisheries operating exclusively in their respective EEZ) are prohibited from intentionally setting nets around whale sharks and cetaceans. If they are unintentionally encircled in the net, they must be safely released.
There is currently too little data to carry out stock assessments for shark species, so the scientific committee recommends better monitoring and a precautionary approach to their management. 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. Hooking mortality is apparently very high for bigeye and pelagic threshers, therefore the prohibition on retaining of any part of thresher sharks on-board and promoting live release of thresher shark may be largely ineffective for species conservation. In 2018 IOTC introduced a new measure on management of blue shark stocks, requiring better data collection on catches and discards and paving the way to consider additional management measures in 2021. Transshipment of oceanic whitetips and thresher sharks is prohibited. Countries must develop conservation and management measures for vulnerable shark species. A number of countries are currently incorporating a ban on the retention of oceanic whitetip sharks into national legislation 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 all turtle species in the Indian Ocean is concerning. The scientific committee advises that maintaining or increasing fishing effort in the Indian Ocean without appropriate mitigation measures in place will likely result in further declines in biomass, and recommends that appropriate mechanisms are developed to ensure compliance with data collection and reporting requirements. Turtles must be released wherever possible and countries are requested to research other mitigation techniques.
Interactions with all vulnerable non-target species should be recorded. 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 2019, of the 34 members of IOTC, 16 countries had completed national plans of action (NPOAs) for sharks, 7 for seabirds and 11 for turtles. Click here to see which countries had and had not fully implemented NPOAs.
Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.Anchovy, anchovies
Herring or sild
Horse Mackerel, Scad
Salmon, Atlantic (Farmed)
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
ReferencesACAP, 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].
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].
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].
Fishery Progress, 2019. Fishery Improvement Project Directory. Available at https://fisheryprogress.org/ [Accessed on 28.11.2019].
IOTC, 2019. Draft resource stock status summary - yellowfin tuna: Status of the Indian Ocean yellowfin tuna (YFT: Thunnus albacares) resource, IOTC-2019-SC22-ES04. Presented to the 22nd Indian Ocean Tuna Commission Scientific Committee, 2-6 December 2019, Karachi, Pakistan. 4pp. Available at https://iotc.org/documents/SC/22/ES03E [Accessed on 28.11.2019].
IOTC, 2017. Report of the 13th Working Party on Ecosystems and Bycatch, IOTC-2017-WPEB13-R, for the Indian Ocean Tuna Commission, 4-8 September 2017, San Sebastian, Spain. 124pp. Available at http://www.iotc.org/meetings/13th-working-party-ecosystems-and-bycatch-wpeb13 [Accessed 21.11.2017].
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. 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. Paper IOTC-2019-SC22-06[E] presented to the 22nd Indian Ocean Tuna Commission Scientific Committee, 2-6 December 2019, Karachi, Pakistan. 11pp. Available at https://iotc.org/documents/SC/22/06E [Accessed on 27.11.2019].
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. Review of the statistical data and fishery trends for tropical tunas. Paper IOTC-2019-WPTT21-08_Rev1 presented to the 21st Indian Ocean Tuna Commission Working Party on Tropical Tunas, 21-26 October 2019, Donostia-San Sebastian, Spain. 57pp. Available at https://iotc.org/WPTT/21/Docs/08-DATA [Accessed on 28.11.2019].
ISSF, 2019. Status of the world fisheries for tuna. Oct. 2019. ISSF Technical Report 2019-12. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2019-12-status-of-the-world-fisheries-for-tuna-october-2019/ [Accessed on 26.11.2019].
IPNLF, 2012. Ensuring sustainability of live bait fish, International Pole and Line Foundation, London, 57 pp.
Restrepo, V., Dagorn, L., Itano D., Justel-Rubio A., Forget F. and Moreno, G., 2017. A summary of bycatch issues and ISSF mitigation initiatives to-date in purse seine fisheries, with emphasis on FADs. ISSF Technical Report 2017-06. International Seafood Sustainability Foundation, Washington, D.C., USA.