Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Purse seine (FAD & Free School)
Capture area — Pacific, Eastern Central (FAO 77), South, East (FAO 87) and West (FAO 81)
Stock area — Eastern Pacific
Stock detail — All Areas
Picture of Tuna, skipjack

Sustainability rating four info

Sustainability overview

Skipjack tuna is a notoriously difficult species to assess. As skipjack and bigeye tuna stocks have similar characteristics, skipjack status can be inferred from bigeye status, as long as bigeye fishing mortality is below the MSY level. The 2018 assessment of bigeye indicates that the stock is being overfished, so skipjack status cannot be inferred from bigeye status and so data limited scoring has been applied for the stock status criteria. There is concern regarding increasing exploitation rates following two years of record high catches and whilst there is also some concern over the declining average weight of skipjack, there is reportedly not yet any credible risk to the skipjack stock. In 2016 interim Harvest Control Rules were brought in for bigeye, skipjack and yellowfin purse seine fisheries, with the aim of preventing fishing effort from exceeding maximum sustainable yield (MSY) for the species that requires the strictest management; for other fisheries, management measures will be as consistent as possible with the purse seine fishery. In 2017, it was acknowledged that the commission had failed since 2013 to reduce fishing mortality of yellowfin and bigeye (adjusted for capacity) to a level not exceeding MSY. MSY is unknown for skipjack. Over 99% of skipjack tuna in the EPO is caught by purse seiners, 70% of it on FADs. Bigeye, caught alongside skipjack is subject to overfishing. The proportion of bycatch of vulnerable species is low in purse seine fisheries in the EPO (less than 0.5% for sharks), yet the overall catch of sharks is still significant and better monitoring and reporting is needed from the smaller purse seiners. FADs can also entangle sharks and turtles, but FAD construction and overall management is improving. There is 100% observer coverage on large purse seiners, but small purse seiners have no observer requirement and data from them is very poor.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to improve the management of FADs and status of bycatch and other tuna species caught with skipjack. 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. There are some Marine Stewardship Council (MSC) certified fleets within this area which represent the best option. There are also some Fisheries Improvement Projects (FIPs) for purse seine fleets operating in this area which are making good progress to address some key environmental issues and aim to achieve MSC certification. Further info about these FIPs 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

Eastern Pacific

Stock information

The skipjack stock in the Eastern Pacific Ocean (EPO) is assessed by the Inter-American Tropical Tuna Commission (IATTC). Skipjack tuna is a notoriously difficult species to assess. Due to its high and variable productivity, it is difficult to detect the effect of fishing on the population with standard methods, and this is particularly true for the stock of the EPO. The IATTC Scientific Committee suggests that conducting a well-planned and executed comprehensive tagging study is the only way to address this. According to the scientific committee, of primary concern for this stock is the constantly increasing exploitation rate. Whilst this appears to have levelled off in recent years and consequences have not emerged, the average weight of skipjack has been declining since 2000, reaching levels last seen in the early 1980s. In 2015 and 2016 it was below the lower reference level, but increased in 2017. Any continued decline in average length would be a concern and should a levelling off of catch or CPUE occur it may indicate that the exploitation rate is near or above the level associated with MSY. However, in this case the decline in weight is likely due to the large recruitments in 2015 and 2016. Following two years of record high catches (342,557t in 2016), the 2017 provisional catch of 327,979t is a reduction, but is still higher than the previous 5 year average (299,935t).

The Last update to the stock assessment was 2014. It indicated that the stock was healthy and not subject to overfishing, but there remained considerable uncertainty in this. As skipjack and bigeye tuna stocks have similar characteristics, skipjack status can be inferred from bigeye status, as long as bigeye fishing mortality is below the MSY level. The 2018 assessment of bigeye indicates that the stock is being overfished, so skipjack status cannot be inferred from bigeye status. However, neither analyses of current tagging data, nor the use of various models, indicate credible risk to skipjack stocks. Implementing the proposed large-scale tagging program in the EPO for 2019-2023 is critical to obtain an assessment of this stock.

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 achieve 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 Inter-American Tropical Tuna Commission (IATTC). 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.

In 2016 interim Harvest Control Rules were brought in for bigeye, skipjack and yellowfin purse seine fisheries, with the aim of preventing fishing effort from exceeding FMSY for the species that requires the strictest management. For other fisheries, management measures will be as consistent as possible with those for the purse seine fishery. Further evaluation of this HCR and alternatives will be conducted, so that a permanent HCR can be adopted.

In 2017, it was acknowledged that the commission had failed since 2013 to reduce fishing mortality of yellowfin and bigeye (adjusted for capacity) to a level not exceeding MSY: fleet capacity in 2017 was estimated to be about 6.7% greater than the previous three-year average. Management measures were updated accordingly, in line with recommendations: the 62-day closure for large purse seiners was extended to 72 days annually until 2020. However, in 2018 a new bigeye stock assessment indicated that the stock was now subject to overfishing, and while the assessment was too uncertain to recommend further extensions of the closure, indications are that current measures remain insufficient to prevent overfishing. Scientific recommendations are for the total number of purse seine sets (FAD and non-FAD) to be limited to 14,895 in 2019 and 14,498 in 2020, with only dolphin-associated sets allowed once this limit is reached. These have yet to be adopted by the commission, although there are per-vessel limits on the number of FADs that can be active at any one time (between 70 and 450, depending on vessel size) and regular reporting on FAD activity is required.

Until 2020, there is a 30-day closure of an area known as the “Corralito” (west of the Galapagos Islands, where catch rates of small bigeye are high) to the purse-seine fishery for yellowfin, bigeye, and skipjack tuna.

A requirement to retain and land all bigeye, skipjack, and yellowfin tuna caught by purse seine has been extended until 2020, although the degree of enforcement regime may vary depending on the country or authority.

For skipjack, the increasing effort and catches, and the decreasing mean size of the fish in the catch, are cause for concern and the scientific committee recommends a comprehensive tagging program for tropical tunas in the EPO.

There is 100% observer coverage on large purse seiners. The scientific committee recommends an additional observer programme for small purse seiners, to obtain better data on discards and bycatch, as well as investigations into an electronic monitoring system on all purse seiners for better data on species, sizes, and quantities of target and bycatch species.

To help address IUU, the IATTC maintains an IUU Vessel List; maintains a register of authorised fishing vessels; and prohibits transhipments at sea for most vessels (some exemptions apply) and requires most other transhipments to be documented and observed as part of the regional observer programme. Countries are required to report annually on monitoring, control and compliance of management measures. The IATTC and WCPFC endeavour to work together to promote compatibility between their respective conservation and management measures across the Pacific.

Capture Information

Criterion score: 0.75 info

99% of the skipjack landings in the Eastern Pacific Ocean (EPO) are from purse seining: 70% on floating objects including Fish Aggregation Devices (FADs), and 29% on free schooling fish.

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 and the method can also be associated with bycatch of vulnerable species, in particular sharks. In the EPO, the bycatch of sharks comprises a small proportion of the total catch of tuna, but as the volume of tuna caught is high, the catch of sharks is still significant.

FAD-associated purse seining generally encounters higher bycatch rates compared with sets on free-schools, and higher proportions of juvenile tuna. It’s unknown if the widespread use of FADs has other impacts such as on the natural species composition of tuna schools, migratory patterns, growth rates and predation rates of affected pelagic species. The 2018 assessment of yellowfin tuna, caught alongside skipjack, indicates that the stock is subject to overfishing. Poorly designed FADs can also entangle animals like sharks and turtles.

Bycatch mitigation measures such as sorting grids are in place to reduce mortality of turtles, sharks and non-target species in general. From Jan 2015, all purse seiners using FADs in the EPO must record and report to the authorities details relating to the FAD design, deployment, catch and bycatch summaries for each set. Additionally, FAD design is required to be non-entangling so as to minimise interaction with turtles and sharks and is encouraged to be made from biodegradable materials. Further restrictions to reduce the entanglement of sharks, sea turtles or any other species come into force in January 2019. Vessels are prohibited from knowingly setting a purse seine around tuna schools associated with a live whale shark and if a whale shark is incidentally encircled, all reasonable steps must be taken to ensure its safe release. Details of the interaction are to be recorded, as are details of any interactions with sharks and turtles. Permissible sharks are to be fully utilized and no more than 5% of fins to total shark weight can be retained; landing oceanic whitetip, silky sharks and mobula rays is prohibited and vessels must not fish in silky shark pupping areas. In 2016 IATTC introduced stricter monitoring and reporting of catches of shark species, but the scientific committee continues to advise that shark data collection is inadequate and must be improved - it is currently not possible to assess the state of most sharks and mobulid ray species. The scientific committee also recommends that experiments be conducted on mitigating bycatches of sharks, especially in longline fisheries, and on the survival of sharks and mobulid rays captured by all gear types, with priority given to those gears with significant catches. There is 100% observer coverage on large purse seiners in the EPO so the data coming from these fleets should be useful and of high quality. Data from small purse seiners is very poor and 20% observer coverage is recommended for them as well.

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
Salmon, Atlantic (Farmed)
Salmon, Chinook, King Salmon
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Coho , Silver, White
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
Sprat, whitebait
Swordfish
Trout, Rainbow
Tuna, albacore
Tuna, bigeye
Tuna, skipjack
Tuna, yellowfin

References

Fishery Progress, 2018. Fishery Improvement Project Directory. Available at https://fisheryprogress.org/ [Accessed on 05.12.2018].

Froese, R. and D. Pauly. Editors. 2018. FishBase version (06/2018). Available at www.fishbase.org [Accessed on 10.12.2018].

IATTC, 2018. Inter-American Tropical Tuna Commission: Active IATTC and AIDCP Resolutions and Recommendations. Available at https://www.iattc.org/ResolutionsActiveENG.htm [Accessed on 05.12.2018].

IATTC, 2018. Staff recommendations for management and data collection. Document SAC-09-15 Rev 2 for the Inter-American Tropical Tuna Commission Scientific Advisory Committee, Ninth Meeting, 14-18 May 2018, La Jolla, California, USA, 15 pp. Available at https://www.iattc.org/Meetings/Meetings2018/SAC-09/9th-Meeting-Scientific-Advisory-Committee.htm [Accessed on 05.12.2018].

IATTC, 2018. Tunas, Billfishes and Other Pelagic Species in the Eastern Pacific Ocean in 2017. Document IATTC-93-01 for the Inter-American Tropical Tuna Commission 93rd meeting, 24 and 27-30 August 2018, San Diego, California. 115 pp. Available at https://www.iattc.org/Meetings/Meetings2018/IATTC-93/IATTC-AIDCP-Annual-Meetings-AUG2018ENG.htm [accessed on 05.12.2018].

ISSF, 2018. Status of the world fisheries for tuna: October 2018. ISSF Technical Report 2018-21. International Seafood Sustainability Foundation, Washington, D.C., USA. 103 pp. Available at: https://iss-foundation.org/about-tuna/status-of-the-stocks/ [Accessed on 06.12.2018].

Maunder, M., 2018. Updated indicators of stock status for skipjack tuna in the eastern Pacific Ocean. Document SAC-09-07 Rev. for the Inter-American Tropical Tuna Commission Scientific Advisory Committee, Ninth Meeting, 14-18 May 2018, La Jolla, California, USA, 4pp. Available at https://www.iattc.org/Meetings/Meetings2018/SAC-09/9th-Meeting-Scientific-Advisory-Committee.htm [Accessed on 05.12.2018].

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.