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Tuna, yellowfin

Thunnus albacares

Method of production - Caught at sea
Capture method - Purse seine (non FAD associated)
Capture area - Indian Ocean (FAO 51,57)
Stock area - Indian Ocean
Stock detail - All Areas
Certification -
Fish type - Oily fish

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This fish, caught by the methods and in the area listed above, is the least sustainable fish to eat and should be avoided. Click on the rating icon above to read more and on the alternatives tab below to find sustainable fish to eat.


Sustainability overview

In 2016, the Indian Ocean Tuna Commission (IOTC) undertook an expedited stock assessment to update the previous one undertaken in 2015 for Indian Ocean yellowfin. The 2016 assessment indicated that the stock was still overfished and subject to overfishing, albeit to a lesser extent than the 2015 assessment suggested. An interim plan for rebuilding the stock was agreed in 2016 to come into effect at the start of 2017. The measures are expected to reduce catches by approximately 10% yet according to projections, this is unlikely to reduce fishing mortality to sustainable levels nor rebuild the population.

Whilst the majority of the catch is taken by EU flagged purse seiners (mainly FAD sets from Spain then France), substantial catches are also take in longline, handline and gillnet fleets from various IOTC nations

The most selective methods include: handline, troll, pole and line, and then non-FAD free purse seine shots. Bycatch of vulnerable species is of serious concern in the gillnet fisheries which are largely unmanaged. Bycatch remains of concern in longline fisheries and FAD associated purse seine sets which encounter a greater proportion of bycatch and juvenile fish compared with non-FAD purse seine sets. Monitoring and reporting of interactions with vulnerable bycatch species needs improvement across all fleets.

Biology

Tuna belong to the family Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Yellowfin are found throughout the world's tropical and subtropical seas, except the Mediterranean. They often form large, size specific schools, frequently associated with dolphins or floating objects. Yellowfin is a large fast growing species, reaching maximum sizes of 240cm in length, 200kg in weight and an age of 8 years. They mature when 2 to 5 years old and mainly spawn in summer. Smaller fish are mainly limited to surface waters, while larger fish are found in surface and deeper waters, but rarely below 250m. Yellowfin has medium resilience to fishing.

Stock information

Stock area
Indian Ocean

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Stock information
Indian Ocean stocks are managed by the Indian Ocean Tuna Commission (IOTC). In 2016, the Indian Ocean Tuna Commission (IOTC) updated their 2015 stock assessment for Indian Ocean yellowfin tuna. The update was more optimistic than the 2015 assessment and includes more reliable information on catch rates of longline fisheries as well as updated catch data up to 2015, which results in a lower estimate of fishing mortality in the NE Indian Ocean. However, it still indicates that the stock is overfished and subject to overfishing (spawning biomass, SB was estimated to be at 0.89 SB MSY and fishing mortality, F at 1.11 F MSY - in 2015, SB was estimated to be 0.66 and F was 1.34). Spawning stock biomass in 2015 was estimated to be 28.9% of the unfished levels. Catches in 2015 were 407,575t - below the estimated maximum sustainable yield of 422,000t. The increase in longline, gillnet, handline and purse seine effort and associated catches in recent years has substantially increased the pressure on the Indian Ocean stock as a whole, with recent fishing mortality exceeding the MSY-related levels. There is an 88% chance that the stock will remain overfished if catches increase or remain at 2015 levels until 2018. Projections also suggest it likely the stock will remain overfished and subject to overfishing (at least until 2025) with a 10% reduction in catches (from 2015 levels).

Management

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. Retained yellowfin catch and/or effort data is poor or unknown for the following countries/fisheries including: many coastal fisheries, notably those from Indonesia, Sri Lanka, Yemen, and Madagascar; the gillnet fisheries of Iran and Pakistan; longliners of India; the fresh-tuna longline fishery of Indonesia; the gillnet and longline fishery of Sri Lanka; and other non-reporting industrial purse seine and longline vessels.

An interim plan for rebuilding the Indian Ocean yellowfin tuna stock will come into force at the beginning of 2017. While there are reductions in catches, they do not meet the recommendation of the scientific committee (reduce catch to 80% of the 2014 levels). Catch reductions vary by gear, and apply to countries whose catch by the respective gear exceeds a certain threshold (indicated in brackets): purse seine: reduce to 85% of 2014 levels (5,000t), gillnet: reduce to 90% of 2014 levels (2,000t), longline: reduce to 90% of 2014 levels (5,000t), other gears: reduce to 95% of 2014 levels (2,000t). Countries will determine their own methods for achieving these reductions and report them back to the Commission. The effects of this measure will be assessed in 2018. Previous management of the catch and effort did not appear to have been effective as catches far exceeded scientific advice in recent years.

Other IOTC conservation and management measures of note for yellowfin in the Indian Ocean include:

A ban on the discarding of bigeye, yellowfin and skipjack tunas by purse seine vessels.

Regarding the use of Fish Aggregation Devices (FADs): In 2016, a maximum limit of 425 drifting Fish Aggregation Devices (dFADs) that can be in use at any one time by each purse seiner was implemented (reduced from 550 in 2015). A maximum of 850 can be acquired each year (down from 1100 in 2015). Greater reporting requirements are now also required by both vessels using FADs and countries that have FAD fishing vessels. Countries must submit FAD management plans that outline how they are to minimise mortality of juvenile yellowfin and bigeye tuna and vulnerable non-target species such as sharks, turtles and rays. From 2016, each FAD is also to be marked with a unique identification number.

In 2016 IOTC prohibited the use of aircrafts and unmanned aerial vehicles as fishing aids, which significantly contribute to the fishing effort of tuna fishing vessels by increasing their fish detection capacity.

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 part of the Programme to Monitor Transhipments at Sea, which requires a list of approved and authorised vessels to undertake transhipments to be maintained. Additionally, the programme requires all transhipments at sea to be monitored by an IOTC observer.

Capture information

Between 2012 and 2015, purse seiners primarily from the European Union accounted for approximately 34% of the average catch of yellowfin tuna in the Indian Ocean (20% associated with Fish Aggregating Devices, FADs, and 13% on free swimming schools). In recent years, the proportion of the purse seine catch taken on floating objects (Fish Aggregation Devices - FADs) has been increasing, peaking in 2013 at 101,906t. At the same time, purse seine catches on free schooling fish have fluctuated between 30,000t and 60,000t.

Purse seines generally target smaller fish than longlining and often catch large numbers of juvenile fish. Yellowfin is often taken in purse seine sets targeting the smaller skipjack tuna. The IOTC scientific committee has noted that the increasing proportion of juvenile yellowfin being caught, particularly in FAD purse seine fisheries, has reduced the maximum sustainable yield.

Purse seines are associated with lower mortality rates of sharks, turtles and certainly birds, compared with longlining; however their widespread use means they may still have a significant impact on turtles, sharks and dolphins. FAD associated purse seine fisheries catch a higher proportion of juvenile fish and non-target species compared with sets on free schooling tuna. There are measures employed to reduce bycatch such as sorting grids, yet improved monitoring is required to assess their effectiveness. Poorly designed FADs may also entangle sharks and turtles. The increasing use of FADs is of concern due to the unknown impacts such gear might have on natural migratory patterns, growth rates and predation rates of affected pelagic species. Research into this should be prioritised.

In 2016, a maximum limit of 425 drifting Fish Aggregation Devices (dFADs) that can be in use at any one time by each purse seiner was implemented (reduced from 550 in 2015). A maximum of 850 can be acquired each year (down from 1100 in 2015). Greater reporting requirements are now also required by both vessels using FADs and countries that have FAD fishing vessels. Countries must submit FAD management plans that outline how they are to minimise mortality of juvenile yellowfin and bigeye tuna and vulnerable non-target species such as sharks, turtles and rays. From 2016, each FAD is also to be marked with a unique identification number. Whilst a limit is certainly needed, this number will most likely not restrict current FAD usage significantly.

Regarding sharks, participating members are to develop conservation and management measures for vulnerable shark species which includes the prohibition to retain, tranship or land certain species and requires details of interactions with these species to be logged. This already applies to thresher sharks and, as in most tuna RFMOS, oceanic whitetip sharks. Monitoring of these measures is currently deficient and in 2016 the scientific committee recommended better monitoring and a precautionary approach to management of shark species. Several countries have failed to implement national plans for sharks, seabirds and turtles as required (although the shark plan is not binding in India as they have objected to the measure).

In 2016 IOTC introduced a number of resolutions to improve compliance with existing management measures, e.g. observer coverage, catch and effort reporting, support for countries to implement measures. Click here to see which countries have and have not fully implemented plans and actions for seabirds, sharks and marine turtles: http://www.iotc.org/documents/status-development-and-implementation-npoas-seabirds-and-sharks-and-implementation-foa.

There is also ban on the discarding of bigeye, yellowfin and skipjack tunas by purse seine vessels under IOTC jurisdiction.

Read more about capture methods


References
Froese, R. and D. Pauly. Editors. 2016. FishBase. Available at www.fishbase.org [Accessed Dec 2016].

IOTC, 2016. Conservation and management measures. Available at http://www.iotc.org/cmms [Accessed Dec 2016].

IOTC, 2015. Status of development and implementation of national plans for seabirds and sharks, and implementation of FAO guidelines to reduce marine turtle mortality in fishing operations. Available at http://www.iotc.org/sites/default/files/documents/2015/11/IOTC-2015-SC18-06E_-_Status_of_NPOAs.pdf [Accessed Dec 2015].

IOTC, 2016. Status of the Indian Ocean yellowfin tuna (YFT: Thunnus albacares) resource. Executive summary. Available at http://www.iotc.org/science/status-summary-species-tuna-and-tuna-species-under-iotc-mandate-well-other-species-impacted-iotc [Accessed Dec 2016].

ISSF, 2016. Status of the world fisheries for tuna: management of tuna stocks and fisheries, 2016. ISSF Technical Report 2016-14. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at http://iss-foundation.org/downloads/13305/ [Accessed Nov 2016].

ISSF, 2016. Tuna stock status update, 2016: Status of the world fisheries for tuna. ISSF Technical Report 2016-05B. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at http://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2016-05b-status-of-the-world-fisheries-for-tuna-nov-2016/ [Accessed Nov 2016].

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