Capture method — Troll
Capture area — Indian Ocean, Western (FAO 51) and Eastern ( FAO 57)
Stock area — Indian Ocean
Stock detail — All Areas
A stock assessment for Indian Ocean yellowfin tuna was carried out in 2018, indicating that the stock was overfished and subject to overfishing. Spawning stock biomass in 2017 was estimated to be 30% of the unfished levels. Provisional catch in 2017 was 409,101t - a little above the estimated maximum sustainable yield of 403,000t and higher than the 2013-2017 average of 399,830 t. Projections indicated that if 2017 catch levels were to be maintained there would be a high 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. 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. About 4% of the catch comes from troll fisheries. Trolling is a very selective method of fishing and typically uses less baitfish than pole & line.
Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to improve reporting, local management and to recover the yellowfin stock. Some troll, handline and pole & line fleets here are in a Fishery Improvement Project making progress at improving elements of the fishery. More info about these FIPs is available from fisheryprogress.org.
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). There is some uncertainty in these estimates. Spawning stock biomass in 2017 was estimated to be 30% of the unfished levels. Provisional catch in 2017 was 409,101t - a little above the estimated maximum sustainable yield of 403,000t and higher than the 2013-2017 average of 399,830 t.
Projections indicated that if 2017 catch levels were to be maintained there would be a high 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. 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.
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. In 2015 and again in 2018 the scientific committee recommended that the catches of yellowfin tuna should be reduced by 20% of the reported 2014 levels (which were 396,635t), to recover stocks to sustainable levels with 50% probability by 2024. In 2017 and 2018 the measures in force were estimated to achieve only a 10% reduction from 2014 levels. In addition, some countries may have inaccurately reported their catches as being below certain thresholds so as to escape some measures. These measures include:
Countries whose 2014 catches exceeded certain thresholds must reduce their catches by a certain amount compared to 2014 levels: Purse seine, if over 5000 t in 2014, reduce to 85% of 2014 levels; Gillnet, if over 2000 t, reduce to 90%; Longline, if over 5000 t, reduce to 90%; Other gears, if over 5000 t, reduce to 95%. Countries will determine their own methods for achieving these reductions and report them back to the Commission.
In addition, the number of supply vessels (these vessels increase fishing capacity) is limited to 50% of the number of purse seine vessels in 2018-2019 and 40% in 2020-2022. The 2018 stock assessment indicates that the stock remains overfished and subject to overfishing, and that current catches remain unsustainable.
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 was reduced from 550 in 2015 to 425 in 2016 and has been 350 since 2017. The maximum that can be acquired each year was reduced from 1100 in 2015 to 850 in 2016 and has been 700 since 2017. 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. 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. From 2016, each FAD must be marked with a unique identification number.
There is a freeze on capacity to 2006 levels which extends to vessels greater than 24m in length, or vessels under this length operating in international waters. This is to be reviewed in 2018.
5% regional observer coverage is required for all vessels over 24m and for vessels under 24m fishing outside of their Exclusive Economic Zone (EEZ).
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 info
Trolling is a small scale method of fishing which uses lures or baited hooks attached to single lines which target tuna near the surface. It’s a labour intensive and very selective form of fishing and currently accounts for approximately 4% of the yellowfin catch in the Indian Ocean.
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
Salmon, Atlantic (Farmed)
Salmon, Chinook, King Salmon
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Coho , Silver, White
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
ReferencesFishery Progress, 2019. Fishery Improvement Project Directory. Available at https://fisheryprogress.org/ [Accessed on 27.02.2019].
Fu, D., Langley, A., Merino, G., Ijurco, A. U., 2018. Indian Ocean yellowfin tuna SS3 model projections. IOTC-2018-SC21-16 for the 21st Meeting of the Scientifc Committee of the Indian Ocean Tuna Commission, 3-7 December 2018, Mahe, Seychelles. 6 pp. Available at http://www.iotc.org/meetings/21st-scientific-committee-sc21 [Accessed on 13.12.2018].
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. Compendium of Active Conservation and Management Measures for the Indian Ocean Tuna Commission, 04 October 2018. Avaiable at http://www.iotc.org/cmms [Accessed on 6.12.2018].
IOTC, 2018. Draft Resource Stock Status Summary Yellowfin Tuna, Status of the Indian Ocean yellowfin tuna (YFT: Thunnus albacares) resource, IOTC-2018-SC21-ES04 for the 21st Meeting of the Scientifc Committee of the Indian Ocean Tuna Commission, 3-7 December 2018, Mahe, Seychelles. 3 pp. Available at http://www.iotc.org/meetings/21st-scientific-committee-sc21 [Accessed on 04.12.2018].
IOTC, 2018. Nominal Catches Database / Base de donnes captures nominales of the Indian Ocean Tuna Commission. Available at http://www.iotc.org/data/datasets [Accessed on 13.12.2018].
IOTC, 2018. Outcomes of the 22nd Session of the Indian Ocean Tuna Commission, IOTC-2018-SC21-03 [E], 21-25 May 2018, Bangkok, Thailand. 4 pp. Available at http://www.iotc.org/meetings/22nd-session-indian-ocean-tuna-commission-s22 [Accessed on 04.12.2-18].
IOTC, 2018. Report of the 20th Session of the IOTC Working Party on Tropical Tunas, IOTC-2018-WPTT20-R[E], for the Indian Ocean Tuna Commission, 29 October - 3 November 2018, Mahe, Seychelles. 127 pp. Available at http://www.iotc.org/meetings/20th-working-party-tropical-tunas-wptt20 [Accessed on 22.11.2018].
IOTC, 2018. Report of the 22nd Session of the Indian Ocean Tuna Commission, IOTC-2018-S22-R[E], 21-25 May 2018, Bangkok, Thailand. 144 pp. Available at http://www.iotc.org/meetings/22nd-session-indian-ocean-tuna-commission-s22 [Accessed on 04.12.2-18].
ISSF, 2018. Status of the world fisheries for tuna: October 2018. ISSF Technical Report 2018-21. International Seafood Sustainability Foundation, Washington, D.C., USA. 103 pp. Available at: https://iss-foundation.org/about-tuna/status-of-the-stocks/ [Accessed on 06.12.2018].