Tuna, skipjack

Euthynnus pelamis, Katsuwonus pelamis

Method of production — Caught at sea
Capture method — Pole & line
Capture area — Indian Ocean (FAO 51,57)
Stock area — The Republic of Maldives EEZ
Stock detail

Certified fleets only


Certification

Marine Stewardship Council (MSC)


Picture of Tuna, skipjack

Sustainability rating one info

Sustainability overview

The last stock assessment for Indian Ocean skipjack was undertaken in 2017 and indicated that the stock was in a healthy state, but great uncertainty was noted. Skipjack stocks are notoriously difficult to assess and some countries in the Indian Ocean do not report fishery data which is important for stock assessment and management. The Maldives though, has been proactive with the management of its fisheries resources. A harvest control rule and Total Allowable Catch (TAC) have come into effect in 2018 for Indian Ocean skipjack, representing a large step forward in management and important measure to safeguard this important fishery. Monitoring and mitigation of vulnerable bycatch species is fairly poor in the wider Indian Ocean and observer coverage is also relatively low. Pole & line fishing is very selective but does contribute to catches of juvenile yellowfin and bigeye, and does rely on a substantial amount of small live fish for bait. The total catch of bait fish is relatively low compared to targeted fisheries and is unlikely to overexploit these stocks, but could have implications for local availability. Monitoring, documentation and commitments associated with the Maldivian MSC certified fishery enable better scoring for capture method and management and represents the best choice for skipjack.

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

The Republic of Maldives EEZ

Stock information

Skipjack and other tuna stocks in the Indian Ocean are assessed by IOTC - the Indian Ocean Tuna Commission. Catches of skipjack in the Indian Ocean increased dramatically from 50,000t in 1980 to over 600,000t in 2006, coinciding with the widespread use of Fish Aggregation Devices (FADs) in the purse seine fisheries. Since then, catches have been relatively stable at around 400,000t, although the provisional figure for 2016 is slightly higher at 446,723 t. The reduction since 2006 has been partially attributed to piracy in the western Indian Ocean (especially in waters near Somalia, Kenya, Tanzania and the Maldives).

A new assessment was carried out for skipjack tuna in 2017, which differs from the previous (2014 and 2011) assessments owing to improvements to the model and inclusion of new data. There remains considerable uncertainty in the assessment, but as with the previous assessments the skipjack tuna stock is determined to be not overfished (spawning stock biomass is at the target level of 40% of unexploited levels) and is not subject to overfishing (catches in 2016 as well as the 2012-2016 average are lower than the catch associated with the proxy for FMSY of 510,000 t). It is worth noting though that the stock has declined due to lower than expected recruitment in the recent period and it is unclear if recruitment will return to the expected levels in the near future.

Given the current status of the fishery and assuming that catch does not exceed recommended levels, it would be expected that the stock would fluctuate around the target level. Fluctuations in catch per unit effort, mainly for the purse seine, coincide with changing environmental conditions. Due to its specific life traits, skipjack can respond quickly to foraging conditions driven by ocean productivity. The scientific committee recommends that environmental indicators should be closely monitored to inform on the potential increase/decrease of stock productivity.

Management

Criterion score: 0 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; for this stock it is the Indian Ocean Tuna Commission (IOTC). There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. 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.

There are persistent failures by some countries to report to the commission annually, including reporting catch data, and other issues with lack of data and poor quality data persist.

The Maldives has demonstrated a strong commitment to sustainably managing their fisheries and have imposed numerous restrictions on fisheries within their waters, such as a ban on net fishing for tuna and a prohibition of landing all sharks. The pole and line skipjack fishery is the largest and most important fishery for the Maldives and is certified by the Marine Stewardship Council (MSC) as a sustainable and well managed fishery.

IOTC has set targets and thresholds for fishing effort and spawning stock biomass for the species it manages. A Harvest Control Rule (HCR) came into force in 2017, with a target of maintaining the spawning stock at or above 40% of its unfished biomass. It requires stock assessments every 3 years and bases catch limits on those assessments. It also states that maximum Total Allowable Catch (TAC) should never exceed 900,000 t (the upper estimate of MSY based on the 2014 assessment). The TAC for 2018-2020, based on the 2017 stock assessment, is 470,029 t. 2016 catches were below this level.

Other IOTC conservation and management measures of note include:
A ban on the discarding of bigeye, yellowfin and skipjack tunas by purse seine vessels, as well as of non target species such as other tunas and billfish.
A ban on the use of aircrafts and unmanned aerial vehicles as fishing aids, which significantly contribute to fishing effort by helping to detect fish.
A ban on surface or submerged artificial lights for the purpose of aggregating tuna and tuna-like species beyond territorial waters.
In 2012 IOTC banned the use of driftnets on the high seas. In 2022 this will be extended to the entire IOTC area (i.e. within countries’ EEZs as well).
Regarding the use of drifting Fish Aggregation Devices (FADs): The maximum number of drifting FADs that can be in use at any one time by each purse seiner was reduced from 550 in 2015 to 425 in 2016 and 350 in 2017. The maximum that can be acquired each year was reduced from 1100 in 2015 to 850 in 2016 and 500 in 2017. Countries that use FADs must report regularly to the Commission and submit FAD management plans outlining how they will minimise mortality of juvenile yellowfin and bigeye tuna and vulnerable non-target species such as sharks, turtles and rays. To reduce the entanglement of sharks, marine turtles or any other species, the design and deployment of FADs must be based on certain principles: The surface of the FAD should not be covered, or only covered with non-meshed material; If a sub-surface component is used, it should not be made from netting but from non-meshed materials such as ropes or canvas sheets; To reduce the amount of synthetic marine debris, the use of natural or biodegradable materials should be promoted. From 2016, each FAD must be marked with a unique identification number.
There is a freeze on capacity to 2006 levels which extends to vessels greater than 24m in length, or vessels under this length operating in international waters. This is to be reviewed in 2018.
5% regional observer coverage is required for all vessels over 24m and for vessels under 24m fishing outside of their Exclusive Economic Zone (EEZ).
To help address IUU, the IOTC maintains an active vessel register and an IUU Vessel List and prohibits transhipments for large scale vessels at sea unless they are pre-approved, monitored by an observer and the vessel uses a Vessel Monitoring System (VMS).

In 2016 IOTC introduced a number of resolutions to improve the poor compliance with existing management measures, e.g. observer coverage, catch and effort reporting, support for countries to implement measures.

Capture Information

Criterion score: 0 info

In 2016 around 15% of skipjack catches in the Indian Ocean were from pole and line fisheries, almost all of it from the Maldives. All Maldivian vessels licensed for pole and line fishing within the 200 mile Maldives EEZ are included in the MSC certified fishery, which therefore covers 100% of Maldivian pole and line caught skipjack tuna. Pole and line fishing effort in the Maldives increased significantly from the 1970s including an increase in boat size and power and the use of anchored Fish Aggregation Devices (FADs) since 1981. In 2006, the maximum catch of about 136,000t was recorded. In recent years though, pole and line catches for skipjack have decreased corresponding with the development of the handline fishery for the larger yellowfin tuna.

Pole and line fishing consists of a bamboo or plastic pole, 10 to 15 feet in length, with a line and a feathered barbless hook attached to the smaller end of the pole, capable of handling a fish weighing below 23kg. Bycatch is relatively low in these fisheries, yet can be greater when used in conjunction with Fish Aggregation Devices (FADs). Pole and line fishing is a very selective method of fishing, yet it does depends on significant quantities of bait fish to attract the tuna. In the Maldivian targeted skipjack pole and line fishery it has been estimated that for each tonne of bait fish, roughly seven tonnes of skipjack are caught. In this fishery, the primary bait fish used is silver sprat. Whilst this species is a small and relatively resilient to overfishing, there is a need to ascertain what impact their use as bait may have on the stock and to develop some basic management measures.

References

IOTC, 2017. Report of the 21st session of the Indian Ocean Tuna Commission, IOTC-2017-S21-R[E], 22-26 May 2017, Yogyakarta, Indonesia. 114 pp. Available at http://www.iotc.org/meetings/21st-session-indian-ocean-tuna-commission-s21 [Accessed 21.11.2017] .

IOTC, 2017. Report of the 13th Working Party on Ecosystems and Bycatch, IOTC-2017-WPEB13-R, for the Indian Ocean Tuna Commission, 4-8 September 2017, San Sebastian, Spain. 124pp. Available at http://www.iotc.org/meetings/13th-working-party-ecosystems-and-bycatch-wpeb13 [Accessed 21.11.2017].

IOTC, 2017. Status of the Indian Ocean skipjack tuna (SKJ: Katsuwonus pelamis) resource, IOTC-2017-SC20-ES03, for the 20th Scientific Committee of the Indian Ocean Tuna Commission, 30 November - 4 December 2017, Mahe, Seychelles. 3 pp. Available at http://www.iotc.org/meetings/20th-scientific-committee-sc20 [Accessed 21.11.2017].

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

Murua, H., Kitakado, T., Mosqueira, I., Adam, S., Merino, G., Fu, D., Bentley N., 2017. Calculation of skipjack catch limit for the period 2018-2020 using the Harvest Control Rule adopted in Resolution 16/02, IOTC-2017-SC20-12 Rev_1, for the 20th Scientific Committee of the Indian Ocean Tuna Commission, 30 November - 4 December 2017, Mahe, Seychelles. 3 pp. Available at http://www.iotc.org/meetings/20th-scientific-committee-sc20 [Accessed 21.11.2017].

IOTC, 2017. Review of the statistical data and fishery trends for tropical tunas, IOTC-2017-WPTT19-07, for the Working Party on Tropical Tunas of the Indian Ocean Tuna Commission, 17-22 October 2017, Mahe, Seychelles. 49pp. Available at http://www.iotc.org/meetings/19th-working-party-tropical-tunas-wptt19 [Accessed on 24.11.2017].

MSC, 2017. Marine Stewardship Council: Maldives pole & line tuna. Available at https://fisheries.msc.org/en/fisheries/maldives-pole-line-tuna [Accessed on 20.11.2017].

ISSF, 2017. Status of the world fisheries for tuna: November 2017. ISSF Technical Report 2017-02A. International Seafood Sustainability Foundation, Washington, D.C., USA. 98 pp. Available at: https://iss-foundation.org/about-tuna/status-of-the-stocks/ [Accessed on 20.11.2017].