Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Purse seine (FAD & Free School)
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 three 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).

80% of the skipjack here is caught in purse seine fisheries: 37% from sets around floating objects (FADs), and 43% on free-schooling tuna. Juvenile tuna are often caught in purse seine fisheries and the method is also associated with bycatch of vulnerable species including sharks, turtles and other billfish. The proportion of this bycatch is higher in FAD-associated fisheries, which can also entangle species. Whilst the proportion of this bycatch compared with the total catch is very low, the high volume of tuna that is caught means that even a low proportion of this can still be relatively high in terms of total volume or individuals. Redistribution of effort from FADs to free schools has resulted in substantial reductions in estimated catches of silky shark (by 83%) and oceanic whitetip shark (by 57%). Observer coverage is 100% for purse seiners on the High Seas and between 20 N and S unless fishing exclusively in their national waters, and poor elsewhere.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to reduce impacts to vulnerable species and encourage development of a harvest strategy for skipjack. Large buyers should consider supporting such improvements. There are MSC certified fleets within the scope of this rating which represent the best choice and there is also is a Fishery Improvement Project (FIP) in place for some fleets which is making good progress at improving elements of the fishery. More info about this FIP is available from fisheryprogress.org

MCS advocates specifying the need for supplying vessels to register on the ISSF Proactive Vessel Register.

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

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

Criterion score: 0.5 info

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.
The Parties to the Narau Agreement (PNA), which covers a number of South Pacific Islands and produces 25% of the world’s tuna, has a series of agreements in place to control access to tuna it is waters and increase economic benefits for South Pacific islanders. Their IUU aerial surveillance programme in 2017 covered 100% of the EEZs in their area. 90% of FAD sets in the WCPO were in PNA waters, and FAD density is high - 400-500 FADs in one degree square (roughly 110km sq.) per month. A recent PNA report estimated that 7% of FADs ‘beach’ (with concerns for pollution and navigation safety) and up to 52% were lost (drift outside the fishing ground of the company owning it, at which point the company is likely to abandon it). Therefore, ghost fishing is of concern where FADs have entangling elements.
98% of FADs have echo-sounders, allowing remote monitoring of the biomass near them. There are plans to develop this technology to distinguish between species to enable reduction of fishing mortality on bigeye.
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: 0.75 info

80% of skipjack catches in the WCPO are from purse seine vessels (37% on FADs and 43% on free schools) - a figure which has steadily increased over the last 30 years. Many juvenile fish are often caught in purse seine fisheries and the method is also associated with bycatch of sharks, turtles and dolphins (more so in FAD-associated fisheries, which can also entangle species). Whilst the proportion of this bycatch compared with the total catch is relatively low, the high volume of tuna that is caught means that even a low proportion of this can still be relatively high in terms of total volume or individuals. The widespread use of FADs is also 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. The scientific committee recommends more comprehensive data collection relating to FADs.

No limit reference points are in place for any Pacific sharks, and it is recommended that these be implemented. Species of concern are: Silky sharks, which are subject to overfishing. Pacific bigeye thresher, which seems likely to be experiencing overfishing, primarily from the bigeye tuna fleet. Oceanic whitetip, which is at just 4% of unfished levels, and 9% of the levels needed to achieve Maximum Sustainable Yield. This is a very slight recovery from previous years, but it’s unclear if recovery will continue. Fishing pressure is high but has declined (F:FMSY was 6.12 in 2013 and 2.67 in 2016). The greatest impact on this species is bycatch from longline fisheries, with lesser impacts from purse seining. Further catch mitigation and improved handling and release practices are required. Reduced catch and retention has occurred as a result of the existing management measures, but this has reduced the amount of data coming in about the species. Improving longline observer coverage to greater than 5% is therefore crucial for improving the understanding of the fishery on vulnerable species. To reduce the entanglement of sharks, marine turtles or any other species, and reduce the amount of synthetic marine debris, countries are encouraged to use non-entangling, natural and biodegradable design and materials for FADs, in line with scientific advice. Stricter (i.e. binding) measures may be adopted in 2018. Vessels are prohibited from knowingly setting a purse seine around tuna schools associated with a live whale shark, marine mammal or turtle, and all reasonable steps are required to be taken to ensure the safe release of these animals and details of the interaction are to be recorded if accidentally encircled. In 2016, catches of silky sharks in the longline fishery were around three times higher than in the purse seine fishery. Redistribution of effort from FADs to free schools has resulted in substantial reductions in estimated catches of silky shark (by 83%) and oceanic whitetip shark (by 57%). Shark measures include: full utilisation of permissible sharks and retention of no more than 5% of fins to total shark weight (but there is no mechanism in place to assess this); a prohibition to land silky and oceanic whitetip sharks; a prohibition on the use of shark lines. The effectiveness of these measures are difficult to evaluate owing to lack of data. As of 2014, shark management plans are required where sharks are being targeted, although to date only 2 countries have developed them. There are measures to improve recording of manta and mobula rays discarded and released, and to treat these species as key shark species for assessment and research. In 2017 the scientific committee recommended guidelines for safe release of manta and mobulid rays, which were adopted by the WCPFC. The commission is also looking to develop guidelines for other rays and sharks, especially silky shark and oceanic whitetips, as well as develop stronger and more comprehensive management measures for sharks, but there is no stated deadline for this.

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].