Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Pole & line
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 two info

Sustainability overview

Updated: November 2020

Skipjack in the Indian Ocean is currently not in an overfished state, and not subject to overfishing. However, recent catches have been well above the catch limits and this lack of control is concerning. A harvest control rule is in place for this fishery, but management measures are clearly not controlling fishing pressure on the stock. 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, around 20% of Indian Ocean skipjack catches were by pole and line fishing. This method of fishing targets fish near the surface, and so rarely touches the seabed and doesn’t have habitat impacts. It is labour-intensive and very selective, meaning there are low levels of bycatch of vulnerable species. However, some fishing takes place on Fish Aggregating Devices, which can have bycatch risks and also increase the catch of the overfished yellowfin tuna. Most of the pole-and-line-caught Indian Ocean skipjack is from the well-managed Marine Stewardship Council certified fishery in the Maldives. A Fishery Improvement Project for Indonesian pole & line skipjack is underway to improve monitoring and reduce impacts there. More info about the 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 (40cm 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 info

Indian Ocean skipjack is not overfished and not subject to overfishing, despite recent large catches tht exceeded the catch limits.

This stock is managed by the Indian Ocean Tuna Commission (IOTC). A new stock assessment was carried out in 2020, using data up to 2019. Catches for Indian Ocean skipjack gradually increased from the 1950s to the 1980s, staying below 100,000 tonnes. They then sharply increased to over 600,000t in 2006, before dropping to around 350,000t in 2012. Another peak followed, again reaching 600,000t in 2018. These dramatic fluctuations in catches correspond with significant drops in the biomass of the spawning portion of the stock (spawning biomass, SB). SB is estimated to have dropped from very high levels in the 1980s to below target levels in the early 2010s. It has since recovered, and is estimated to be 11% above the target level, which is a spawning stock size of 40% of unfished levels (SSB 2019:SSB 40%SSB0 = 1.11). Meanwhile, the exploitation rate (E) has contuously increased, exceeding target levels in the mid-2010s and only recently falling just below them again. In 2019, E was 92% of target levels, which is an exploitation rate consistent with keeping the stock at 40% of unfished levels (E 2019:E 40%SSB0 = 0.92). The new target limit according to the 2020 assessment is 536,000t, an increase on the preivous assessment, which indicated a limit of 510,100t. Catches in 2018 and 2019 (547,248 t) exceeded this and the 2018 -2020 TAC (470,029t), which is of concern for future management of this stock.

Due to its specific life history attributes, skipjack can respond quickly to ambient foraging conditions driven by ocean productivity, which seem to have been favourable in recent years. Environmental indicators should be closely monitored to inform on the potential increase/decrease of stock productivity. 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).

Management

Criterion score: 0.75 info

Skipjack in the Indian Ocean is currently not in an overfished state, and not subject to overfishing. However, recent catches have been well above the catch limits and this lack of control is concerning. A harvest control rule is in place for this fishery, but management measures are clearly not controlling fishing pressure on the stock. 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 of the pole-and-line-caught Indian Ocean skipjack is from the Marine Stewardship Council certified fishery in the Maldives. There have been concerns over the lack of logbooks and reporting in this fishery - in 2017, only 20% of logbooks were returned. In 2019 the Maldives introduced new legislation making it mandatory to submit logbook data prior to offloading catch. This is a positive step, but more time is needed to see if this improves compliance in the fishery. In addition to this, in 2020 conditions were added to the certification requiring the fishery to develop Harvest Control Rules for skipjack, and to ensure that catch limits are complied with. A Fishery Improvement Project for Indonesian pole & line skipjack is underway to improve monitoring and reduce impacts of the fishery. More info about the FIP is available from fisheryprogress.org.

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.

IOTC has set targets and thresholds for fishing effort and spawning stock biomass for the species it manages, which is positive. Even more encouragingly, a Harvest Control Rule (HCR) for skipjack came into force in 2017, with a target of maintaining the stock at or above 40% of unfished levels. Catch limits are based on stock assessments, carried out every 3 years. The Total Allowable Catch for 2018-2020, based on the 2017 stock assessment, is 470,029 t. Catches in 2018 (600,000t) and 2019 (provisionally 547,248t) have significantly exceeded it. This lack of control and enforcement is of significant concern, and undermines the potential of a Harvest Control Rule to keep the stock at sustainable levels. 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. Skipjack catches by the purse seine fishery increased by 43% from 2017 to 2018.

On average from 2015-2019, purse seining accounted for around 53% of skipjack catches: 42% using Fish Aggregating Devices (FADs) and 2.4% 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: 0.25 info

On average from 2015-2019, around 20% of Indian Ocean skipjack catches were by pole and line fishing. This method of fishing targets fish near the surface, and so rarely touches the seabed and doesn’t have habitat impacts. It is labour-intensive and very selective, meaning there are low levels of bycatch of vulnerable species.

Pole and line fishing consists of a bamboo or plastic pole, 10 to 15 feet in length, with a line and a feathered barbless hook attached to the smaller end of the pole, capable of handling a fish weighing below 23kg. It can use large quantities of live fish for bait, which could have impacts on baitfish populations. Most of the pole-and-line-caught Indian Ocean skipjack is from the Marine Stewardship Council certified fishery in the Maldives. The main baitfish species being used is silver sprat, as well as small amounts of blue sprat, anchovy, fusiliers and cardinalfish. This is a fairly well-monitored fishery, with baitfish catches being recorded in logbooks, unlike in many other pole and line fisheries. The Maldives also has a livebait management plan and it is not thought that any of the baitfish species are being put at risk by the fishery. It is estimated that between 3.5 and 7.7kg of sprat are used to catch 100kg of skipjack.

Pole and line fishing effort in the Maldives increased significantly from the 1970s, and there was an increase in boat size and power and the use of anchored Fish Aggregation Devices (FADs) from 1981. In 2006, the maximum catch of about 136,000t was recorded. In recent years though, pole and line catches for skipjack have decreased to around 110,000t corresponding with the development of the handline fishery for the larger yellowfin tuna. FADs can be associated with bycatch, for example by entangling vulnerable species, although this is more of a concern with drifting FADs than anchored ones. There is also some catch of the overfished yellowfin tuna stock in this fishery, which again is more likely when fishing around FADs. The Maldives has also set limits on yellowfin catches, although it is not clear what actions will be taken when the limits are reached. It has also limited the number of FADs, all of which are anchored, to 50. It is taking steps to encourage pole and line fishing on free schools instead of FADs, to further reduce risks of bycatch.

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].

Criquet, G., Stokes, K. and Halim, A., 2020. Marine Stewardship Council (MSC) 2nd Surveillance Report: Maldives pole & line skipjack tuna, September 2020. Prepared by SAI Global on behalf of Maldives Seafood Processors & Exporters Association (MSPEA). 54pp. Available at https://fisheries.msc.org/en/fisheries/maldives-pole-line-skipjack-tuna/@@assessments [Accessed on 07.12.2020].

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].

Fu, D. 2020. Preliminary Indian Ocean Skipjack Tuna Stock Assessment 1950-2019 (Stock Synthesis). IOTC–2020–WPTT22–10. 57pp. Available at https://iotc.org/sites/default/files/documents/2020/10/IOTC-2020-WPTT22AS-10_Rev1.pdf [Accessed on 04.12.2020].

ISSF, 2020. Status of the world fisheries for tuna. Nov. 2020. ISSF Technical Report 2020-16. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2020-16-status-of-the-world-fisheries-for-tuna-november-2020/ [Accessed on 10.12.2020].



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, 2019. Report of the Seventh Session of the IOTC Working Party on Temperate Tunas: Assessment Meeting. IOTC-2019-WPTmT07(AS)-R[E]. 23-27 July 2019, Shizuoka, Japan. 37pp. Available at https://iotc.org/documents/WPTmT/702/R_E [Accessed on 27.11.2019].

IOTC, 2020. Draft Resource Stock Status Summary: Skipjack Tuna (SKJ: Katsuwonus pelamis). IOTC–2020–SC23–ES03. 4pp. Available at https://iotc.org/documents/skipjack-tuna [Accessed on 04.12.2020].

IOTC 2020, Outcomes of the 24th Session of the Commission. IOTC2020-SC23-03 [E]. 4pp. Available at https://iotc.org/documents/SC/23/03E [Accessed on 04.12.2020].

IOTC, 2020. Report of the 16th Working Party on Ecosystems and Bycatch, IOTC-2020-WPEB16-R[E], for the Indian Ocean Tuna Commission, 7-10 September 2020, Online. 105pp. Available at https://iotc.org/documents/SC/23/WPEB16RE [Accessed 04.12.2020].

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].

IPNLF, 2012. Ensuring sustainability of live bait fish, International Pole and Line Foundation, London, 57 pp.

ISSF, IPNLF, 2019. Skippers’ Guidebook to Pole-and-Line Fishing Best Practices. Version 1.0 - April 2019. International Seafood Sustainability Foundation and International Pole & Line Foundation. Available at http://ipnlf.org/perch/resources/pl-guidebookipnlfissffinal.pdf [Accessed on 30.11.2020].