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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
Accreditation -
Fish type - Oily fish

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This fish, caught by the methods and in the area listed above, is not the most sustainable choice of fish to eat. Click on the rating icon above to read more and on the alternatives tab below to find more sustainable fish to eat.


Sustainability overview

The updated Indian Ocean yellowfin assessment in 2012 indicated the fishery was in a healthy state, yet the scientific committee recommended catches should not exceed 300,000t to ensure the biomass remained at a healthy level. Estimated catches for 2012 however, of 368,663t, are considerably above both the 2011 catch of 327,490t and the five year mean of 317,505 t and above the estimated Maximum Sustainable Yield (MSY) of 344,000t suggesting that the stock could now be subject to overfishing. The scientific committee note that it is difficult to determine this at the moment and a new assessment may be required. Increased catches have been observed across the range of gears accessing the fishery, yet has been most obvious in the handline and non-FAD purse seine catches with 2012 catches nearly double those recorded in 2009. Choose yellowfin from the pole and line and troll fisheries, as these are relatively selective and have also remained stable for several years.

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
In Dec 2012, the Indian Ocean Tuna Commission (IOTC) updated their 2011 assessment of the Indian Ocean yellowfin tuna stock. This assessment suggests that the stock is not being overfished with fishing mortality, F, at 0.61Fmsy or 0.69Fmsy depending on the model. Regarding the state of the biomass, the assessment also suggested that the stock was not in an overfished state, with spawning biomass (SB) estimated to be 1.24 or 1.35SBmsy depending on the model. Between 2003 and 2006 however, fishing mortality far exceeded Fmsy and subsequent reductions in SB between 2004 and 2009 were observed. Reductions in catch and effort in the longline and purse seine fisheries in years following this are most likely attributable to the piracy situation in the western Indian Ocean. It has been noted though, that if this situation changes, and fishing returns to traditional areas, effort is expected to increase once again. The potential yields from the fishery have also declined over the last five years as an increased proportion of the catch is comprised of smaller fish, primarily from the purse seine FAD fishery. In 2012, the scientific committee recommended that catches not exceed 300,000 tonnes, which is at the lower end of the range of MSY estimates. However, estimated catches for 2012 of 368,663t, are considerably above both the 2011 catch of 327,490t and the five year mean of 317,505 t. Additionally, this catch is also above the modelled Maximum Sustainable Yield (MSY) of 344,000t (with a range from 283,000 to 453,000t) suggesting that the stock may now being subject to overfishing. The IOTC state that it is currently difficult to determine this given the recent increased catch rates in some fisheries and stabilisation in others and that a new stock assessment in 2014 may be required.

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. Yellowfin catch and/or effort data is poor or unknown for the following countries/fisheries: Indonesia, Sri Lanka, Yemen, and Madagascar; the gillnet fishery of Pakistan; non-reporting industrial purse seiners and longliners of India; the fresh-tuna longline fishery of Indonesia, the gillnet fisheries of Iran and Pakistan; significant gillnet/longline fishery of Sri Lanka; important coastal fisheries using hand and/or troll lines, in particular Yemen, Indonesia, and Madagascar.

There is no harvest control rule that has been developed for the stock, however a request has been made to the scientific committee to develop one. Interim limit and target reference points have been made for the stock which are to be assessed and reviewed at the 2014 annual meeting. A harvest control rule would certainly aid in limiting catches, which have in recent years far exceeded scientific advice and estimates of MSY.

The main binding conservation measure established by the IOTC for bigeye is a one month closure for purse seiners and longliners (over 24m in length or fishing on the high seas) in an area of size 10°x20°. The effect of the closure on the status of IO tuna stocks cannot be evaluated yet, but preliminary analyses based on historical catches indicate its effect is likely to be very small. There is also ban on the discarding of bigeye, yellowfin and skipjack tunas by purse seine vessels.

Other IOTC conservation and management measures of note include:

5% regional observer coverage is required for all vessels over 24m and for vessels under 24m fishing outside of their Exclusive Economic Zone (EEZ).

Regarding the use of Fish Aggregation Devices (FADs): FAD management plans are required to be developed which include the development of more detailed reporting of catch sets on FADs and development of improved FAD designs to reduce entanglement of non-target species such as sharks and turtles.

Regarding bycatch: longline fisheries are to employ prescribed bycatch mitigation measures, in some a combination are to be used (eg tori line, dyed bait, weighted branch line, night setting, underwater setting chute). 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 the effectiveness of these measures is to reviewed in 2016.

From 2014 purse seines will be prohibited from knowingly setting a purse seine around tuna schools associated with a live whale shark or cetacean. Furthermore, if a whale shark or cetacean is incidentally encircled, all reasonable steps are required to be taken to ensure its safe release and details of the interaction are to be recorded.

To help address IUU, the IOTC maintains 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

Purse seining is commonly an industrial scale fishery used to catch tuna destined for canneries. Many juvenile fish are often discarded in purse seine fisheries and the method is also associated with bycatch of sharks, turtles and cetaceans. Purse seine catches have been decreasing and account for approximately 35% of yellowfin catches in the IO, with 17% taken in purse seine fisheries that target free schooling fish, as opposed to using Fish Aggregation Devices (FADs). FAD associated catches have a higher proportion of juvenile fish and bycatch including vulnerable species. Poorly designed FADs may also entangle sharks and turtles. It has also been reported that the use of FADs may impact on the biology (food intake, growth rate, plumpness of the fish) and on the ecology (displacement rate, movement orientation) of yellowfin. Non FAD associated purse seiners still encounter bycatch , yet on a much smaller scale compared with FAD fisheries.

Read more about capture methods


References
IOTC, 2013. Report of the Sixteenth Session of the IOTC Scientific Committee. Busan, Rep. of Korea, 2–6 December 2013. Available at http://www.iotc.org/files/proceedings/2013/sc/IOTC-2013-SC16-R[E].pdf [Accessed Dec 2013].
ISSF, 2013. ISSF Tuna Stock Status Update, 2013(2): Status of the world fisheries for tuna. ISSF Technical Report 2013-04A. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at http://iss-foundation.org/resources/downloads/?did=487 [Accessed Nov 2013].
IOTC, 2012. Report of the Fifteenth Session of the IOTC Scientific Committee. Mahé, Seychelles, 10–15 December 2012. IOTC–2012–SC15–R[E]:288pp.

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