Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

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, skipjack

Sustainability rating four info

Sustainability overview

Updated: November 2019 

The most recent assessment for Indian Ocean skipjack tuna was carried out in 2017, and as with the previous assessments indicated that the stock is not overfished (spawning stock biomass is at the target level of 40% of unexploited levels) and is not subject to overfishing. The 2016 catch was 446,723t, below the target level of 510,100t (which is consistent with the level of fishing pressure expected to keep the biomass at the target level of 40%). However, catches have recently dramatically increased: while the 2012-2016 average was 407,456t, 2017 catch was 524,282t and provisional 2018 catch was 607,701t. This is well above the target level and the 2018 -2020 TAC (470,029t). The next stock assessment is due in 2020. A harvest control rule is in place for this fishery, but management measures are clearly not controlling fishing pressure on the stock. The stock has declined due to lower than expected recruitment in the recent period and it is unclear if recruitment will return to the expected levels in the near future. 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 40% of skipjack tuna catch here: 49% using Fish Aggregating Devices (FADs) and 1% on free-schooling fish. Yellowfin is often taken in purse seine sets targeting the smaller skipjack tuna and is in an overfished state. 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 than longlining, however their widespread use means they may still have a significant impact on bycatch 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 is generally insufficient in the IOTC and observer coverage is relatively low at 5% for all vessels over 24m and for vessels under 24m fishing on the High Seas.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to improve monitoring and management of their fisheries, including reducing bycatch of vulnerable species, and specify the need to see ongoing, demonstrable improvements. Large buyers should consider supporting such improvements. There is a Fisheries Improvement Project (FIP) covering a large proportion of the purse seine fleet for this fishery. More info about this FIP 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. Skipjack tuna are found throughout the world’s tropical and warm temperate waters. During the day they school on the surface (often with birds, drifting objects, sharks, whales etc.) but at night can descend to depths of 260m. Skipjack tuna are a very fast growing species, maturing at 2 to 3 years old (40 cm in length) and living for up to 12 years. They can grow up to 100cm and 34kg in weight but are rarely found larger than 80cm and 10kg. They spawn all year round and have a medium to high resilience to fishing.

Stock information

Criterion score: 0.25 info

Stock Area

Indian Ocean

Stock information

Skipjack and other tuna stocks in the Indian Ocean are assessed by IOTC - the Indian Ocean Tuna Commission. Catches of skipjack in the Indian Ocean increased dramatically from 50,000t in 1980 to over 600,000t in 2006, coinciding with the widespread use of Fish Aggregation Devices (FADs) in the purse seine fisheries. After that, catches were relatively stable at around 400,000t. The reduction since 2006 has been partially attributed to piracy in the western Indian Ocean (especially in waters near Somalia, Kenya, Tanzania and the Maldives).

The most recent assessment for Indian Ocean skipjack tuna was carried out in 2017, which differs from the previous (2014 and 2011) assessments owing to improvements to the model and inclusion of new data. There remains considerable uncertainty in the assessment, but as with the previous assessments the skipjack tuna stock is determined to be not overfished (spawning stock biomass is at the target level of 40% of unexploited levels) and is not subject to overfishing. The 2016 catch was 446,723t, below the target level of 510,100t (which is consistent with the level of fishing pressure expected to keep the biomass at the target level of 40%). However, catches have recently dramatically increased: while the 2012-2016 average was 407,456t, 2017 catch was 524,282t and provisional 2018 catch was 607,701t. This is well above the target level and the 2018 -2020 TAC (470,029t). The next stock assessment is due in 2020.

Fluctuations in catch per unit effort, mainly for the purse seine fleet, coincide with changing environmental conditions. Due to its specific life traits, skipjack can respond quickly to foraging conditions driven by ocean productivity. The scientific committee recommends that environmental indicators should be closely monitored to inform on the potential increase/decrease of stock productivity.

Management

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. A Harvest Control Rule (HCR) for skipjack came into force in 2017, with a target of maintaining the spawning stock at or above 40% of its unfished biomass. It requires stock assessments every 3 years and bases catch limits on those assessments. The Total Allowable Catch for 2018-2020, based on the 2017 stock assessment, is 470,029 t. 2016 catches were below this level, but 2017 and 2018 catches (524,282t and provisional 607,701t respectively) have significantly exceeded it. The next stock assessment is due in 2020. Skipjack catches by the purse seine fishery increased by 43% from 2017 to 2018. The scientific committee has suggested that the rebuilding plan for yellowfin and associated restrictions has displaced activity onto purse seines with fish aggregating devices, which has led to an associated increase in skipjack catches.

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.

Capture Information

Criterion score: 0.75 info

Purse seine fishing in 2018 accounted for 50% of skipjack tuna catch: 49% using Fish Aggregating Devices (FADs) and 1% on free-schooling fish. Skipjack catches by the purse seine fishery increased by 43% from 2017 to 2018. The scientific committee has suggested that the rebuilding plan for yellowfin and associated restrictions has displaced activity onto purse seines with fish aggregating devices, which has led to an associated increase in skipjack catches.

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. 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.

Alternatives

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
Arctic char
Herring or sild
Mackerel
Salmon, Atlantic (Farmed)
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
Swordfish
Trout, Rainbow
Tuna, albacore
Tuna, skipjack
Tuna, yellowfin

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].

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, 2018. Fishery Improvement Project Directory. Available at https://fisheryprogress.org/ [Accessed on 05.12.2018].

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].

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.

IOTC, 2019. Draft Resource Stock Status Summary - Skipjack Tuna: Status of the Indian Ocean skipjack tuna (SKJ: Katsuwonus pelamis) resource, IOTC-2019-SC22-ES03. 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, 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].

MSC. 2019. Marine Stewardship Council: Maldives pole & line skipjack tuna. Available at https://fisheries.msc.org/en/fisheries/maldives-pole-line-skipjack-tuna [Accessed on 28.11.2019].

Zhu, J. and Toshihide, K., 2019. Uncertainties in the 2019 stock assessment for Indian Ocean albacore tuna and suggestions of further researches in 2020 for improving the assessment and providing management advice. Paper IOTC-2019-SC22-13 presented to the 22nd Indian Ocean Tuna Commission Scientific Committee, 2-6 December 2019, Karachi, Pakistan. 5pp. Available at https://iotc.org/documents/SC/22/13 [Accessed on 27.11.2019.].