Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Purse seine (FAD & Free School)
Capture area — Atlantic, North (FAO 27), Central (FAO 34) and South (FAO 47) Eastern
Stock area — East Atlantic
Stock detail — All Areas
Picture of Tuna, skipjack

Sustainability rating four info

Sustainability overview

Updated: December 2019 

Skipjack stocks are difficult to assess. The last stock assessment was carried out in 2014, but no reliable estimate of the maximum sustainable yield (MSY) could be provided. MSY may be increasing, but more slowly than the growth rate of catches. It is unlikely that the eastern skipjack stock is overexploited or experiencing overfishing, but a new stock assessment is needed. The Scientific Committee recommends that the catch and effort levels do not exceed the level of 2012-2013 catch or effort (around 218,434 t). The provisional catch in 2018 (282,427t) exceeds this level by 29%. There is concern regarding the under-reporting of skipjack catches in the Atlantic. There are no specific management measures for skipjack in the ICCAT area, but several time/area regulatory measures intended to protect juveniles of yellowfin and bigeye tuna exist.

About 86% of the catch is taken in purse seine fisheries, mostly setting on FADs. FAD sets catch a greater amount of juvenile bigeye and yellowfin which is reducing the productivity of these stocks. The proportion of bycatch of vulnerable species is relatively low in purse seine fisheries, (e.g.. less than 1.5% for sharks in the Atlantic), yet the overall catch is still significant (especially sharks) and better data collection is needed. The status of some sharks is in the area is unknown and some are overexploited. FADs can also entangle sharks and turtles, but FAD construction and overall management is improving. 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.

Commercial buyers should establish what measures the flag state 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. MCS also advocates specifying the need for supplying vessels, in particular purse seiners, to register on the ISSF Proactive Vessel Register.

Parts of the purse seine fleet for this fishery are in a Fishery Improvement Project (FIP) which is making progress on improving elements of the fishery. 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: 0.25 info

Stock Area

East Atlantic

Stock information

There are two skipjack stocks in the Atlantic - one in the east and one in the west. Both are assessed and managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). In all the oceans, traditional stock assessment models are difficult to apply to skipjack because of their particular biological and fishery characteristics. In order to overcome these difficulties, several assessment 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.

The last stock assessments for east and west Atlantic skipjack were carried out in 2014 using data up to 2013. For eastern skipjack, no reliable estimate of the maximum sustainable yield (MSY) could be provided. MSY may be increasing, but more slowly than the growth rate of catches. It is unlikely that the eastern skipjack stock is overexploited, but it is possible that current catches are at or even above MSY. There is no evidence of a fall in yield, or in the average weight of individuals captured. No projections are available to indicate the effect of current catches on this stock, but they are continually increasing and are above scientific recommendations. The next stock assessment is due in 2020.

Numerous changes have occurred in the east Atlantic skipjack fishery since the early 1990s (e.g. the progressive use of Fish Aggregating Devices and expansion of the fishing area), which has increased the proportion of the biomass exploited. East Atlantic catches have steadily increased from 112,000 tonnes in 2006 to 245,000t in 2017. 2018 catch was 282,427t - a 15% increase on 2017 and a 25% increase on the 2013-2017 average (226,000t). It is also 29% greater than the scientific recommendation, which is to keep catches at 2012 levels (218,000 tonnes). These figures include estimates for discards and small skipjack (37 cm), landed as ‘faux poissons’ in Cote d’Ivoire, which have increased from 10,000t annually from 2005-2014 to 20,000t annually since.

Underreporting has been a problem in the fishery, and corrections have been applied to try to account for this. There has been a sharp increase in purse seine catch, particularly on FADs, in part due to piracy in the Indian Ocean displacing fleets into the Atlantic. Estimates of the unreported catches of these purse seiners have increased since 2006 and may have exceeded 20,000 t for the three main species of tropical tunas. The scientific committee has expressed the need for the countries and the industry in the region to cooperate to estimate and report these catches accurately to ICCAT.

The steady decrease in average weight up to 2011 is consistent with the fact that the purse seine fleet has increased pressure on juvenile tunas. This trend has reversed since 2012 but generally, except in the East Pacific, average skipjack weight in the East Atlantic (2kg) is much lower than the estimates for other oceans (3kg).

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 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.

For eastern skipjack, no reliable estimate of the maximum sustainable yield (MSY) could be provided. It is unlikely that the eastern skipjack stock is overexploited, but it is possible that current catches are at or even above MSY. There is no evidence of a fall in yield, or in the average weight of individuals captured. No projections are available to indicate the effect of current catches on this stock, but they are continually increasing and are above scientific recommendations. The scientific committee recommends that the catch and effort levels do not exceed the level of 2012-2013 catch or effort, but 2018 catch is 29% above this level. In addition, increasing harvests and fishing effort for skipjack could lead to involuntary consequences for other species that are caught in combination with skipjack in certain fisheries (particularly juveniles of yellowfin and bigeye). There is concern regarding uncertainties which the underreporting of skipjack catches may have on the perception of the state of the stocks - estimates of the unreported catches of some purse seiners have increased since 2006 and may have exceeded 20,000 t for the three main species of tropical tunas. In spite of this advice, and attempts by the scientific committee to develop a Harvest Control Rule (HCR) for the eastern stock, no TAC (Total Allowable Catch) or HCR is in place for skipjack.

The following measures are in place for bigeye, skipjack and yellowfin:
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.
A multi-annual management programme has been in place for bigeye and yellowfin since 2012, and eastern skipjack since 2015. Fishing for these species using aggregation devices, including FADs, was prohibited from 1st January to 28th February in an area off the west African coast to reduce catches of juvenile bigeye and yellowfin, for the rest of the year vessels were limited to 500 FADs. 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. The FAD closure was extended to the full convention area, lasting 2 months in 2020 and 3 months in 2021.
Countries must have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem.
ICCAT maintains a list of vessels over 20m authorised to fish for these species, although other vessels may retain them as bycatch as long as the country sets limits on this and doesn’t exceed its quota.
Performance indicators and evaluations of the projected impact of current management measures are expected in 2017, with adjustments to management following in 2018.
Countries are encouraged to reduce discards.
The increasing use of fish aggregation devices (FADs) in skipjack fisheries since the early 1990s have changed the species composition of free schools. It is noted that, in fact, the free schools of mixed species were considerably more common prior to the introduction of FADs. Furthermore, the association with FADs may also have an impact on the biology (growth rate, plumpness of the fish) and on the ecology (distances, movement orientation) of skipjack and yellowfin (“ecological trap” concept).

Other management measures of note include:
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.
In 2015 a working group was formed to look at ways to reduce juvenile catches of bigeye and yellowfin tuna caught in FAD fishing.
are banned in the Mediterranean.
ICCAT maintains lists of vessels authorised to fish for tuna and tuna-like species in the ICCAT area, and those caught carrying out Illegal, Unreported or Unregulated activities.
At-sea transhipment is prohibited unless pre-authorised and the vessel has an observer on board.
In 2017 ICCAT banned the discarding of skipjack, yellowfin and bigeye.
In 2016 the Commission passed measures to strengthen and streamline its compliance assessment process and to develop a scheme of responses to non-compliance.

Capture Information

Criterion score: 0.75 info

Currently, the major East Atlantic skipjack fisheries are the purse seine fisheries, particularly those of Belize, Curacao, France, Spain, Ghana, Guinea, Panama, and Cabo Verde, followed by the bait boat fisheries of Portugal, Spain, Ghana, and Senegal. Skipjack are captured in association with big eye and yellowfin tuna fisheries. It is difficult to discriminate fishing effort between free schools (composed of large yellowfin tunas) and for FAD fishing (targeting skipjack) in the East Atlantic because fishing strategies can change from one year to the next and in addition, the sea time devoted to activities on FADs and the assistance provided by supply vessels are difficult to quantify. It’s estimated that 7% of East Atlantic skipjack is taken by purse seiners setting on free schools of tuna, and 79% setting on Fish Aggregation Devices (FADs). The proportion of small fish in the catches of East Atlantic skipjack since the onset of FADs has significantly increased, and average retained skipjack weight observed here is approximately 2kg whereas estimates in other oceans are closer to 3kg.

Purse seining is commonly an industrial scale fishery used to catch tuna destined for canneries. These fisheries target smaller fish that aggregate close to the surface, whereas longliners target larger fish that inhabit deeper waters. Many juvenile fish are often caught in purse seine fisheries, mainly skipjack, yellowfin and bigeye. When a high proportion of young fish are removed from a population, the potential maximum catch from a fishery is reduced. The method is also 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. FAD-associated purse seining encounters higher bycatch rates compared with sets on free-schools, and higher proportions of juvenile tuna. 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. Poorly designed FADs can also entangle animals.

ICCAT aims to take an ecosystem-based and precautionary approach to fisheries management. In order to minimize the ecological impact of FADs, in particular the entanglement of sharks, turtles and other non-targeted species, and the release of synthetic persistent marine debris, countries must use non-entangling FADs and phase out non-biodegradable FADs. Countries must have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem.

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. Catch limits are now in place for both northern (39,102t as of 2016) and southern (28,923t as of 2016) blue sharks, with the northern TAC being allocated out 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 overfished throughout the Atlantic, significantly so in the northwest, and for the north Atlantic overall it is predicted to take at least 30 years to recover if there was zero fishing mortality. 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.

Observer coverage was increased in 2019 (see Management) but is still inadequate for purse seiners targeting species other than tropical tunas, and all longliners.

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

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, 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].

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, 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].

ICCAT, 2018. Resolutions, Recommendations and other Decisions. Available at http://www.iccat.es/en/RecsRegs.asp [Accessed on 11.12.2018].

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.