Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Gill or fixed net
Capture area — Pacific, North West (FAO 61) and Central (FAO 71,77)
Stock area — Western and Central Pacific
Stock detail — All Areas
Picture of Tuna, skipjack

Sustainability rating five info

Sustainability overview

Updated: December 2019 

The Western and Central Pacific Ocean (WCPO) skipjack stock supports the largest tuna fishery in the World, accounting for approximately 37% of worldwide tuna landings. It is managed and assessed by the Western and Central Pacific Fisheries Commission (WCPFC). A new stock assessment was carried out in 2019 and continued to show that the stock is not overfished, nor subject to overfishing. Spawning biomass is around 2.5 times the level associated with Maximum Sustainable Yield, but fishing mortality is continuously increasing and spawning biomass has reached its lowest level on record. The skipjack catch in 2018 (1,795,048t) was a 10% increase from 2017 and a 1% decrease from the 2013-2017 average. The commission is looking to establish harvest strategies for key fisheries and stocks but has not yet completed this work and so, as of January 2018 adopted a bridging measure to manage bigeye, yellowfin and skipjack until harvest strategies are in place or February 2021. As part of this, the average spawning biomass for skipjack is to be maintained at the interim target of 50% of unfished levels - it is currently at 44%. There is no Total Allowable Catch (TAC) set, but as skipjack is caught alongside bigeye and yellowfin, primarily in purse seine fisheries, the range of measures and capture method impacts listed for bigeye also apply to skipjack and include limits on vessel days and 5 months of closures for purse seine sets on Fish Aggregation Devices (FADs).

About 12% of the skipjack catch here is taken in various, more subsistence style netting operations such as ring and gill nets. Gillnets used for catching tuna and tuna like species can be 7 km and are known for extremely high bycatch including endangered marine turtles, whales, dolphins and sharks. WCPFC bans the use of gillnets over 2.5km long, but monitoring is poor and a default red rating has been applied.

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

Stock Area

Western and Central Pacific

Stock information

The Western and Central Pacific Ocean (WCPO) skipjack stock supports the largest tuna fishery in the World, accounting for approximately 37% of worldwide tuna landings. It is managed and assessed by the Western and Central Pacific Fisheries Commission (WCPFC).

Skipjack tuna catches in the WCPO increased steadily from 1970 onwards, roughly doubling during the 1980s. After stabilising at around 1 million tonnes during the early 1990s, they increased to a record catch of around 2 million tonnes in 2014. Catches have since levelled off at around 1.75 million tonnes.

The latest stock assessment was carried out in 2019. Recent (2015-2018) spawning biomass (SB) was estimated to be 44% of unfished levels, with a 0% chance of it being below the Limit Reference Point (20%). This is below the interim Target Reference Point (which was defined in 2015 as 50% of unfished levels), as it has been since 2009. Recent (2014-2017) fishing mortality (F) was 45% of the level associated with Maximum Sustainable Yield (FMSY), with a 0% chance of it exceeding FMSY. The stock is therefore not overfished, nor subject to overfishing. Spawning biomass is around 2.5 times the level associated with MSY (SBMSY), but fishing mortality is continuously increasing and SB has reached its lowest level on record. The scientific committee therefore recommends that management is implemented to keep the biomass fluctuating around the TRP, e.g. through a Harvest Control Rule.

The skipjack catch in 2018 (1,795,048t) was a 10% increase from 2017 and a 1% decrease from the 2013-2017 average. Using 2012 purse seine effort levels (and 2012 catches for other gear types) as a baseline, the following projections were calculated in 2019: maintaining baseline levels will result in a decrease in SB to 42% SBF=0. Maintaining SB at between 45% and 55% requires reductions in effort from 2012 levels of 13-40%, leading to increases in spawning biomass of between 3 and 31% and a reduction in yield of 10-22%.

The scientific committee advises that tagging data is a critical component of the skipjack stock assessment and recommend regular large-scale tagging cruises and complementary tag recovery work continue to be undertaken in a way that provides the best possible data for stock assessment purposes.

Management

Most tuna stocks range across and are accessed by numerous coastal states, making harmonised and effective management of these individual stocks very difficult. As a result, 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. The tuna fisheries in the Western and Central Pacific Ocean (WCPO) are managed by the Western and Central Pacific Fisheries Commission (WCPFC). 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.

WCPFC has put in place a lower limit for the spawning biomass of bigeye, skipjack, and yellowfin tuna of 20 percent of unfished levels (SB/SBF=0, aka spawning biomass depletion ratio), below which the stock should not fall. For skipjack there is also an interim target of 50 percent of unfished levels, which was adopted in 2015 and has been reached. The scientific committee recommends reducing fishing mortality on juvenile bigeye and yellowfin in the tropics, through preventing increases in overall fishing mortality, until targets for these two stocks can be agreed. The commission is looking to establish harvest strategies for key fisheries and stocks but has not yet completed this work and so, as of January 2018, a bridging measure is in force to manage bigeye, yellowfin and skipjack - the measure lasts until harvest strategies are in place or until February 2021. As part of this, spawning biomass depletion ratios for bigeye and yellowfin are to be maintained at recent levels (the average from 2012-2015) and skipjack at 50 percent. The bridging measure includes a number of new measures and consolidates some pre-existing ones, and is outlined below.

In the tropical region, between 20 degrees North and 20 degrees South, the following applies:
The use and deployment of FADs is prohibited for 5 months of the year (3 months for Kiribati and the Philippines). VMS polling frequency increases to every 30 minutes during the FAD closure.
Effort limits (in vessel days) apply to purse seining on the high seas (excluding Small Island Developing States, SIDS): limits vary by country. In order not to undermine the effectiveness of this, countries cannot transfer effort into areas outside of this region.
To create an incentive to reduce the non-intentional capture of juvenile fish, to discourage waste and to encourage an efficient utilization of fishery resources, purse seiners must retain on board and then land or transship at port all bigeye, skipjack, and yellowfin tuna (also applies to national waters).
All purse seine vessels operating on the high seas or within national waters in this region must carry an observer. This also applies to purse seiners anywhere in the convention area fishing in waters under multiple countries’ jurisdiction or moving between the high seas and national waters.
The number and capacity of large (over 24m) purse seiners and longliners (with freezing capacity and ice-chilled) operating in this area is frozen to 2016 levels (excluding SIDs and Indonesia).
An evaluation of this measure in 2019 found that it would achieve its targets if bigeye recruitment remains high, but if it declines, fishing mortality will double to above FMSY and biomass has a 20% chance of dropping below the limit reference point. For yellowfin, the measure will marginally fail its aims as SB will experience a small decrease. However, data is not in place to assess whether countries are complying with the legislation.

Other measures that apply to the wider convention area:
The number of drifting FADs with activated instrumented buoys deployed at any one time is limited to 350 per purse seine vessel.
Catch and/or effort limits apply for purse seining within national waters (both the type of limit and the amount vary by country).
There are country-specific limits on longline bigeye catch, and by 2020 hard limits for bigeye and a framework to allocate them amongst countries shall be developed.
Catches by other commercial tuna fisheries for bigeye, yellowfin or skipjack tuna (excluding those taking less than 2,000 tonnes) shall not exceed either the average level for the period 2001-2004 or the level of 2004.

More generally:
There is a requirement to submit FAD management plans, including information on strategies used to implement closures and other measures for reducing mortality of juvenile bigeye. A number of aspects in the bridging measure have been brought forward from previous management measures, and it isn’t clear how well they have been implemented, especially given the ongoing increases in total catch of skipjack. The scientific committee recommends more comprehensive data collection relating to FADs.
Observer coverage on purse seiners is poor in areas not specified in the bridging measure and only 5% coverage is required on longliners greater than 20m in length. 20% is considered to be the minimum to be effective.
To help address IUU, the WCPFC maintains an IUU Vessel List, prohibits transhipments at sea between purse seiners (some exemptions apply) and requires all other transhipments to be documented and 100% observed as part of the regional observer programme.
In 2017 a Compliance Monitoring Scheme was introduced to assess and improve compliance with obligations, and penalise non-compliance.

Capture Information

Criterion score: Critical fail info

12% of the skipjack catch is taken in artisanal ring and gill net fisheries with unconfirmed impacts to bycatch species. Gillnets used for catching tuna and tuna like species can be 7 km and are known for extremely high bycatch including endangered marine turtles, whales, dolphins and sharks. WCPFC bans the use of gillnets over 2.5km long, but monitoring is poor.

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].

Brouwer, S., Pilling, G., Williams, P., WCPFC Secretariat , 2017. Trends in the South Pacific albacore longline and troll fisheries, Document WCPFC-SC13-2017/SA-WP-08 for the Thirteenth Regular Session of the Scientific Committee of the Commission for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean, 9 - 17 August 2017, Rarotonga, Cook Islands. 70 pp. Available at https://www.wcpfc.int/meetings/sc13 [Accessed on 27.11.2017].

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].

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

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].

WCPFC, 2019. Reference document for the review of CMM 2018-01 and development of harvest strategies (bigeye, yellowfin and skipjack tunas). Document WCPFC16-2019-13 presented to the Western and Central Pacific Fisheries Commission Sixteenth Regular Session, 5 - 11 December 2019, Port Moresby, Papua New Guinea. Available at https://www.wcpfc.int/node/44338 [Accessed on 05.12.2019].

WCPFC, 2019. Conservation and Management Measures of the Western and Central Pacific Fisheries Commission. Available at https://www.wcpfc.int/conservation-and-management-measures [Accessed on 05.12.2019].

WCPFC, 2019. Summary Report of the Fifteenth Regular Session of the Scientific Committee of the Western and Central Pacific Fisheries Commission, 12-20 August 2019, Pohnpei, Federated States of Micronesia. 275 pp. Available at https://www.wcpfc.int/meetings/sc15 [Accessed on 05.12.2019].

WCPFC, 2019. Current and projected stock status of WCPO skipjack tuna to inform consideration of an updated target reference point. Document WCPFC16-2019-14 presented to the Western and Central Pacific Fisheries Commission Sixteenth Regular Session, 5 - 11 December 2019, Port Moresby, Papua New Guinea. Available at https://www.wcpfc.int/node/44333 [Accessed on 05.12.2019].