Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Purse seine (FAD associated)
Capture area — Atlantic, Western (FAO 21,31,41)
Stock area — West Atlantic
Stock detail — All Areas
Picture of Tuna, skipjack

Sustainability rating four info

Sustainability overview

Updated: November 2020

Skipjack tuna are notoriously difficult to assess, and often there are high levels of uncertainty. There are two stocks of Atlantic skipjack: east and west. This rating is for the western stock, which hasn’t had a stock assessment since 2014 and owing to Covid disruption isn’t now due to receive the next one until 2022. In 2014, it was thought that the stock was unlikely to be in an overfished state, and unlikely to be subject to overfishing. Catches have since declined, and so MCS does not consider there to be concern for the fishing pressure or biomass. There are no specific management measures for skipjack, and no catch limits. Catches are below recommended limits, but existing management does not ensure that this fishery is appropriately controlled. On average, around 10% of western skipjack catch is by purse seine fishing, and this figure has been declining since 2016. Purse seining is associated with bycatch of species such as sharks, turtles and marine mammals, although less so than longlining. Whilst bycatch may comprise a small proportion of the total catch, the high volume of tuna that is caught means that it can still be significant for these vulnerable species. Bycatch is higher where Fish Aggregation Devices are being used. Poorly-designed FADs can entangle vulnerable species, and can also become lost at sea, continuing to ghost fish and be a source of marine debris. There are measures in place requiring countries to improvement FAD management and reduce these impacts. All large purse seine vessels fishing for tropical tunas must have an observer, which improve understanding of bycatch and help to improve compliance with management measures.

Commercial buyers should establish what measures the flag state or fleet relating to their source is taking to improve data collection, research, monitoring and management of their fisheries and specify the need to see ongoing, demonstrable improvements. Large buyers should consider supporting such improvements.

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: 0.25 info

Skipjack tuna are notoriously difficult to assess, and often there are high levels of uncertainty. There are two stocks of Atlantic skipjack: east and west. This rating is for the western stock, which hasn’t had a stock assessment since 2014 and owing to Covid disruption isn’t now due to receive the next one until 2022. In 2014, it was thought that the stock was unlikely to be in an overfished state, and unlikely to be subject to overfishing. Catches have since declined, and so MCS does not consider there to be concern for the fishing pressure or biomass.

Skipjack stocks in the Atlantic are assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). The last stock assessment was carried out in 2014 using data up to 2013. Catches of West Atlantic skipjack were very low from the 1950s to the late 1970s, then sharply increased to peak at 40,272 t in 1985. They stabilised at around 27,000t. As would be expected, Fishing mortality (F) peaked in 1985 and then declined. In 2014 it was thought to be at around 70% of FMSY, indicating that the stock is not subject to overfishing. While there are large fluctuations, the average abundance (or Spawning Biomass, SB) appears to have been relatively stable since the 1980s. In 2014 it was thought to be around 30% above levels associated with Maximum Sustainable Yield (MSY), and so it is not in an overfished state.

Recent catches have been lower than the long term average, with the 2015-2019 average at 21,500t. Preliminary 2019 catch was 19,272t - the lowest since around 1980. In 2014, Maximum Sustainable Yield was estimated to be around 30,000-32,000t.

In order to overcome the challenges in carrying out stock assessments, several methods have been applied to the two stocks of Atlantic skipjack. Smaller sub-units of stocks are being considered and it is expected that the five year Atlantic Tropical Tuna Tagging Programme (AOTTP) may improve understanding of skipjack stock structures and movement patterns.

Management

Criterion score: 0.75 info

There are no specific management measures for skipjack, and no catch limits. Catches are below recommended limits, but existing management does not ensure that this fishery is appropriately controlled. As there has been no stock assessment since 2014, management of this stock cannot be fully scientifically-informed.

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 address this, Intergovernmental Regional Fisheries Management Organisations (RFMOs) have been established. There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. This stock is managed and assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). 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. There remain large data deficiencies in most tuna and billfish fisheries, particularly with regards to fine scale spatial and temporal data for both target and especially for vulnerable bycatch species. 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 no specific management measures for either of the Atlantic skipjack stocks. The scientific committee recommends that the catch and effort levels for western skipjack do not exceed the maximum sustainable yield (30,000-32,000t). Recent catches have been below this level (around 21,500t). However, there is concern regarding uncertainties which the underreporting of skipjack catches may have on the perception of the state of the stocks. ICCAT measures designed for yellowfin and bigeye are likely to impact skipjack. This includes controls on the purse seine fishery, although purse seining only account for around 10% of catches. Around 87% of catches are from baitboat and other surface fisheries, mostly in Brazil. The average weight (3 to 4.5kg) of skipjack caught in the Western Atlantic is higher than in the East (2 to 2.5kg). This is primarily because the pole and line fleet targets larger fish than FAD associated purse seining. A component of the Brazilian pole and line fleet was assessed for Marine Stewardship Council certification in 2019, but was not successful owing to poor reporting and management structures in place in Brazil.

Other Atlantic-wide measures include: A maximum of 500 purse seine FADs to be active at any one time and countries must have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem. This failed to reduce the mortality of juvenile bigeye and yellowfin tuna so in 2019, to address this, the number of FADs was reduced from 500 to 350 in 2020 and 300 in 2021.
There is a tagging programme to improve stock assessments for tropical tunas and gauge effectiveness of management measures for these species. This helped to improve the quality of the 2019 yellowfin assessment.
In 2017 ICCAT banned the discarding of skipjack, yellowfin and bigeye, so that all fish caught must now be landed.
ICCAT maintains a list of vessels over 20m authorised to fish for this species, although other vessels may retain them as bycatch as long as the country sets limits on this and doesn’t exceed its quota.
In 2019 ICCAT increased observer coverage: large purse seiners targeting tropical tunas must have 100% coverage year round rather than just during the FAD closures, and longline coverage will increase from 5% to 10% in 2022. However, the 5% coverage was not well complied with or enforced by some fleets (although others exceeded it), and even this increase falls short of recommendations for a minimum of 20% for accurate reporting of bycatch. However, standards for electronic monitoring are to be developed by 2021. Purse seine and longline vessels over 20m long are encouraged to increase their observer coverage from the required minimum, and some have. Vessel Monitoring Systems are required for all vessels over 24m.
Drift nets were banned by the EU in 2002 and by ICCAT in the Mediterranean in 2003.
In terms of enforcement and compliance with management measures: in 2016 ICCAT passed measures to strengthen and streamline its compliance assessment process and to develop a scheme of responses to non-compliance. There is also a list of vessels authorised to fish for tuna and tuna-like species in the ICCAT area, and a list of vessels caught carrying out Illegal, Unreported or Unregulated activities. At-sea transhipment is prohibited unless pre-authorised and the vessel has an observer on board.

Capture Information

Criterion score: 0.75 info

On average, around 10% of western skipjack catch is by purse seine fishing, and this figure has been declining since 2016. Purse seining is associated with bycatch of species such as sharks, turtles and marine mammals, although less so than longlining. Whilst bycatch may comprise a small proportion of the total catch, the high volume of tuna that is caught means that it can still be significant for these vulnerable species. Bycatch is higher where Fish Aggregation Devices are being used. Poorly-designed FADs can entangle vulnerable species, and can also become lost at sea, continuing to ghost fish and be a source of marine debris. There are measures in place requiring countries to improvement FAD management and reduce these impacts. All large purse seine vessels fishing for tropical tunas must have an observer, which improve understanding of bycatch and help to improve compliance with management measures.

Purse seining is commonly an industrial scale fishery used to catch tuna destined for canneries. The widespread use of FADs is of concern due to the unknown impacts such gear might have on natural species composition of tuna schools, migratory patterns, growth rates and predation rates of affected pelagic species. In order to minimize the ecological impact of FADs, in particular the entanglement of sharks, turtles and other non-targeted species, and reduce marine pollution from lost gear, countries must use non-entangling FADs and phase out non-biodegradable FADs. Countries must also have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem.

Other management in place to protect vulnerable species include:

For sharks: Countries are required to develop and submit National Plans of Action for the conservation and management of sharks. Sharks must be fully utilised (e.g. no removal of fins); must be released wherever possible (if not being directly targeted); and countries must try to minimise bycatch of sharks (although no gear-specific measures are identified). Catching silky sharks, hammerheads, oceanic whitetips, and bigeye threshers is prohibited, and catching other thresher species is discouraged. Shortfin mako, which is heavily overfished, can be caught and retained if over 180cm for males and 210cm for females, otherwise, they must be released unharmed. An updated assessment in 2019 indicated that shortfin mako is unlikely to recover to healthy levels until 2070, unless size restrictions combined with a fixed Total Allowable Catch were introduced. The maximum catch that would allow recovery by 2070 with a reasonable probability (60%) was 300 tonnes. Regardless of management measures, the stock will continue to decline until 2035. However, in 2019 ICCAT failed to reach agreement on measures to protect this species. For blue shark, catch limits are now in place for both northern (39,102t as of 2016) and southern (28,923t as of 2016) stocks, with the northern TAC being allocated to countries - a first for ICCAT shark stocks. If exceeded, the commission has committed to reviewing the effectiveness of its blue shark management measures, although preliminary catch of northern blue shark in 2016 was 42,117 t. Porbeagle is significantly so in the northwest Atlantic and stock status in the northeast and south Atlantic is unknown. In the northwest, the stock could recover by 2035 under recent catches, but these are likely to be underestimated because dead discards are rarely reported. The main porbeagle-directed fisheries (EU, Uruguay and Canada) have closed, and ICCAT have a recommendation to release live porbeagle unharmed, but it is still caught incidentally and discarded, and also landed by other fleets. Currently there is not enough data to properly assess the status of many pelagic sharks (no assessments have been carried out for the Mediterranean) and more work is needed to understand the effects of entanglement in FADs.

For turtles: Purse seiners must avoid encircling turtles and release them when they do so. The scientific committee has noted that management or turtle bycatch is only in place for purse seine and longline. Measures for other gears are needed to both coordinate methods to avoid them, and to improve data on bycatch.

For marine mammals: there are no specific management measures to protect marine mammals, including cetaceans. ICCAT has not prioritised collecting data on mammal bycatch to date. More needs to be done to understand and reduce the impact of ICCAT fisheries on marine mammals.

In 2019 it was agreed to increase observer coverage for large purse seiners targeting tropical tunas to 100% coverage year-round rather than just during the FAD closures, which is a positive improvement.

References

EC, 2019. European Commission Press: Good news for tuna and blue sharks, 29.11.2019. Available at https://ec.europa.eu/fisheries/press/good-news-tuna-and-blue-sharks_en [Accessed on 09.12.2019].

ICCAT, 2020. Resolutions, Recommendations and other Decisions. Available at http://www.iccat.es/en/RecsRegs.asp [Accessed on 26.11.2020].

Gillett, R., 2012. Report of the 2012 ISSF Workshop: The Management of Tuna Baitfisheries: The Results of a Global Study. ISSF Technical Report 2012-08. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/reports/technical-reports/download-info/issf-technical-report-2012-09-the-management-of-tuna-baitfisheries-the-results-of-a-global-study/ [Accessed on 09.12.2019].

ICCAT, 2019. Report of the Standing Committee on Research and Statistics (SCRS) of the International Commission for the Conservation of Atlantic Tunas, 30 September - 4 October 2019, Madrid, Spain. 459 pp. Available at https://www.iccat.int/Documents/Meetings/Docs/2019/REPORTS/2019_SCRS_ENG.pdf [Accessed on 09.12.2019].

ICCAT, 2020. 2020 SCRS Advice to the Commission, September 2020, Madrid, Spain. 362pp. Available at https://www.iccat.int/Documents/SCRS/SCRS_2020_Advice_ENG.pdf [Accessed on 26.11.2020].

ICCAT, 2020. Report of the 2020 ICCAT Intersessional Meeting of the Sub-Committee on Ecosystems, 4-6 May 2020, Online. 28pp. Available at https://iccat.int/Documents/Meetings/Docs/2020/REPORTS/2020_SC_ECO_ENG.pdf [Accessed on 26.11.2020].

ISSF, 2019. International Seafood Sustainability Foundation Blog: ICCAT Moves to Protect Atlantic Bigeye and Close Gaps in Monitoring and Data Collection, 4 December 2019. Available at https://iss-foundation.org/iccat-moves-to-protect-atlantic-bigeye-and-close-gaps-in-monitoring-and-data-collection/ [Accessed on 09.12.2019].

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].

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].