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) and Eastern ( FAO 57)
Stock area — Indian Ocean
Stock detail

All Areas


Picture of Tuna, skipjack

Sustainability rating three info

Sustainability overview

The most recent assessment for Indian Ocean skipjack tuna was carried out in 2017 and indicated that the stock was not overfished nor subject to overfishing but great uncertainty noted. A harvest control rule and TAC are now in place for this fishery. However, catches have recently begun to increase, with the 2012-2016 average at 407,456 t and the provisional 2017 catch at 524,282 t: above the proxy for MSY of 510,100 t. The 2018 -2020 TAC is 470,029 t, so if the high catch of 2017 were to continue it would be cause for concern. 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 43% of skipjack tuna catch here: 40% using Fish Aggregating Devices (FADs) and 3% on free-schooling fish. Increases in catches and catch rates of purse seiners until 2006 are believed to be associated with increases in fishing power and in the number of drifting FADs used and the technology associated with them. 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. However, catches have recently begun to increase, with the 2012-2016 average at 407,456 t and the provisional 2017 catch at 524,282 t - above the proxy for FMSY of 510,100 t. The 2018 -2020 TAC is 470,029 t, so if the high catch of 2017 were to continue it would be cause for concern. It is worth noting that 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.

Given the current status of the fishery and assuming that catch does not exceed recommended levels, it would be expected that the stock would fluctuate around the target level. Fluctuations in catch per unit effort, mainly for the purse seine, 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: 0.25 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. It also states that maximum Total Allowable Catch (TAC) should never exceed 900,000 t (the upper estimate of MSY based on the 2014 assessment). The TAC for 2018-2020, based on the 2017 stock assessment, is 470,029 t. 2016 catches were below this level.

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 350 in 2017. The maximum that can be acquired each year was reduced from 1100 in 2015 to 850 in 2016 and 500 in 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.

Capture Information

Criterion score: 0.75 info

Purse seine fishing accounts for 43% of skipjack tuna catch: 40% using Fish Aggregating Devices (FADs) and 3% on free-schooling fish. Increases in catches and catch rates of purse seiners until 2006 are believed to be associated with increases in fishing power and in the number of drifting FADs used and the technology associated with them. 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 onboard 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.

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 for sharks, seabirds and turtles as required (although the shark plan is not binding in India as they have objected to the measure). Click here to see which countries had and had not fully implemented plans and actions for seabirds, sharks and marine turtles in 2016: http://www.iotc.org/documents/status-development-and-implementation-npoas-seabirds-and-sharks-and-implementation-foa

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
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
Sprat, whitebait
Swordfish
Trout, Rainbow
Tuna, albacore
Tuna, bigeye
Tuna, skipjack
Tuna, yellowfin

References

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].

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 Skipjack Tuna, Status of the Indian Ocean skipjack tuna (SKJ: Katsuwonus pelamis) resource, IOTC-2018-SC21-ES03 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. Outcomes of the 22nd Session of the Indian Ocean Tuna Commission, IOTC-2018-SC21-16 [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 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].

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.