Tuna, Pacific bluefin

Thunnus orientalis

Method of production — Caught at sea
Capture method — All applicable methods
Capture area — Pacific Ocean (FAO 61,67,71,77,81,87)
Stock area — Pacific Ocean
Stock detail — All Areas
Picture of Tuna, Pacific bluefin

Sustainability rating five info

Sustainability overview

Updated: November 2020

Pacific bluefin tuna has been badly managed in the past, with a lack of regulation and enforcement across its range. Contributing to this has been its extremely high market value, adding plenty of incentive for Illegal, Unreported and Unregulated (IUU) fisheries. In 2010 the stock had dropped to just 1.7% of its unfished levels. Since management measures were brought in in 2011 and made stricter in 2015, biomass has gradually increased to 4.5%, and fishing pressure has decreased. However, it remains heavily overfished, and subject to overfishing. The target is to reach 20% by 2034, and the plan allows for catches to increase if there is a high probability that the target will be achieved. There is currently a greater than 95% probability that they will be achieved. However, the rebuilding plan does not seem to be precautionary. In tuna management, 40% is commonly considered a sustainable level, and 20% the lowest safe limit. Therefore, management is for very slow recovery, with the potential for catch increases, on a highly depleted stock. In addition, catches on juveniles are not being adequately controlled. Due to the state of the stock, a critical fail is triggered and a default red rating applies to all gear types.

Biology

Tuna belong to the family Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Bluefin tuna are the largest of the tuna species, reaching upwards of 680 kg. There are three species in each of the Pacific, Atlantic and Southern Oceans. In all oceans bluefins are known for their impressive migrations, routinely crossing ocean basins. Pacific bluefin tuna are generally smaller than their Atlantic cousins, reaching a maximum length of 3m and a maximum weight of 540kg. Not only do they have a hydrodynamic shape, their pectoral (side) fins can be retracted and, unlike other fish, their eyes are set flush to their body. Pacific bluefin tuna is capable of swimming at speeds of 12 to 18 miles per hour (20-30 km per hour) for brief periods. In the Pacific, tagging studies indicate there is only one stock with a spawning ground off southern Japan. Pacific bluefin tuna spawn between Okinawa (Japan) and the Philippines, in April and August, then migrate over 6,000 nautical miles to the eastern Pacific, eventually returning to their birth waters to spawn. They reach reproductive maturity at around 5 years and 60kg.

Stock information

Criterion score: Critical Fail info

Pacific bluefin tuna is very slowly recovering from extremely low levels, but it remains in a very heavily overfished state. Fishing pressure is too high, although it has reduced. It is thought the stock will continue to rebuild under the current catch levels.

Pacific bluefin tuna (PBF) is assessed by the International Scientific Committee for Tuna and Tuna-like species in the North Pacific (ISC). It has a single Pacific-wide stock managed by both the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC). A new stock assessment was carried out in 2020 using data up to 2018. Historical PBF catch records are poor, but go back as early as 1804 from coastal Japan, and the early 1900s for U.S. fisheries. Catches appear to have peaked before WWII at about 50,000t. After this, they fluctuated widely, reaching a low of 8,500t in 1990 and climbing again to 30,000t in 2005. Catches from 2015-2019 averaged 12,000t, with provisional 2019 catch at 10,940t. Biomass, measured as spawning stock biomass (SSB) has also fluctuated. It steadily declined from 1996 to a historical low of 1.7% of unfished levels in 2010. Since management measures were brought in in 2011 and made stricter in 2015, SSB has gradually increased. It remains at very low levels, with estimates putting it at 4.5% in 2018. There is no reference point to judge the stock status, but the initial rebuilding target is to reach 6.4% by 2024, and then 20% by 2034. Below 20%, according to most common reference points for tuna stocks, it remains outside safe biological limits. Fishing pressure (F) is measured as spawning potential ratio (SPR) - the reproductive potential of fish at the current fishing pressure compared to an absence of any fishing. F was at 1% SPR from 2004-2009, meaning the fishing pressure created a spawning potential of 1% of what it would be without fishing. F has since improved to 14%, but this is still higher than most accepted reference points. There is no set fishing effort level, but to achieve a biomass of 20% of unfished levels, the corresponding F would also be 20%. The stock therefore remains subject to overfishing. However, projections indicate that the stock will recover to the initial target by 2021, ahead of time. The stock is projected to be above 30% by 2034, exceeding the second rebuilding target. The next stock assessment is expected in 2022.

Recruitment of young fish into the stock has been below the historical average for the last ten years. The last good recruitment year was 2008, and moderately good recruitment happened in 2010 and 2016. Recruitment in 2017 and 2018 was low. This makes short-term stock projections more optimistic, as more juveniles (aged 0-2 years) were present at the point of assessment, and recruitment after that time has been worse.

Catches from 1952-2018 have mainly been juvenile PBF. However, management since 2015 has helped to reduce fishing pressure on juveniles. Measures restricting the catch of small fish are more effective than those on large fish in rebuilding the stock.

Conditions in the West Pacific probably influence recruitment, and thus the portions of the juvenile fish there that migrate to the East Pacific, as well as the timing of these migrations. Likewise, conditions in the East Pacific probably influence the timing of the return of the juvenile fish to the west.

The IUCN lists Pacific Bluefin tuna as Vulnerable.

Management

Pacific bluefin tuna has been badly managed in the past, with a lack of regulation and enforcement across its range. Contributing to this has been its extremely high market value, adding plenty of incentive for Illegal, Unreported and Unregulated (IUU) fisheries. In 2010 the stock had dropped to just 1.7% of its unfished levels. Since management measures were brought in in 2011 and made stricter in 2015, biomass has gradually increased to 4.5%, and fishing pressure has decreased. However, the rebuilding plan does not seem to be precautionary. The target is to reach 20% by 2034, and the plan allows for catches to increase if there is a high probability that the target will be achieved. In tuna management, 40% is commonly considered a sustainable level, and 20% the lowest safe limit. Therefore, management is for very slow recovery, with the potential for catch increases, on a highly depleted stock. In addition, catches on juveniles are not being adequately controlled.

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 there are two: the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC). 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. The impact of fisheries in the WCPFC convention area on Pacific bluefin (PBF) tuna are far greater than that of fisheries in the IATTC area, and so management measures by WCPFC are considered to be of greater importance. However, management must be comparable and properly implemented across the entire range of the stock in order for it to be effective.

A Northern Committee working group comprising IATTC, WCPFC and others was established in 2016 to support joint working on Pacific bluefin tuna. IATTC and WCPFC have implemented a rebuilding plan for Pacific bluefin, starting in 2015, with the initial goal of rebuilding the spawning biomass (SB) to the historical median (40,994 t, based on the period 1952-2014) by 2024 with at least 60% probability. This would take the SB to 6.4% of unfished levels. In 2018 it was at 4.5%, and projected to reach 6.4% by 2021, ahead of schedule. A second rebuilding target was adopted in 2018: to reach 20% of unfished levels within 10 years of reaching the initial target, or by 2034, whichever is sooner, with at least 60% probability. Current management measures are on track to achieve this target with 96% probability. The stock is projected to be above 30% by 2034.

There is also a harvest strategy in place for the stock. If the probability of achieving the rebuilding target drops to less than 60%, catches of small fish (below 30kg) should be reduced. If the probability is above 75%, overall catches are allowed to increase (with some restrictions). This potential for increasing catches, even when the stock is as lows as 4.5%, is concerning. In the 2020 stock assessment, recruitment for 2017 and 2018 was estimated to be the lowest since early 1990s. Scientific advice is that future recruitments may remain low until there is sufficient recovery in spawning biomass. Therefore, scientists have urged the commissions to take a precautionary approach to the management of Pacific Bluefin tuna. It should consider the desired rebuilding rate and the catches of small bluefin.

A management strategy evaluation, planned for 2020-2024, couldn’t be started in 2020 because of Covid disruption. However, commitments have been made to keep to the schedule of finishing it by 2024.

In terms of the specific PBF fishery measures:
Small bluefin (under 30kg) should not be more than 50% of total catch. Juvenile Pacific bluefin tuna can weigh up to 85kg, and so this measure does not limit catches on all juveniles.
In WCPFC: North of 20 degrees N, fishing effort and catch limits are frozen to the 2002-2004 average – around 14,000t. Countries can transfer part of the catch limit for small bluefin to large bluefin. The implications of this on the stock are to be reviewed by ISC in 2020. Up to 5% of the catch limit can be carried over to the next year.
In IATTC: The catch limit for 2021 is 3,925t. This is effectively an increase on annual limits, as the previous one was 6,200t for 2019 and 2020. The majority of this is allocated to Mexico (3,500t) and USA (425t). In both cases, catches above a certain level (3,000t for Mexico and 300t for USA) will be removed from their quota for 2022. Other countries can only catch bluefin if they had an under harvest from 2020. Weekly reporting is required once countries reach 50% of their limits, and all are notified when the total catch uptake reaches 75% and 90%. IATTC report 40% catch reductions in their area since 2012 through resolutions and voluntary measures. IATTC’s scientific committee has recommended that WCPFC do more to limit catches of adult bluefin.
A joint WCPFC-IATTC catch documentation scheme (CDS) was developed in 2019 to help combat IUU, which is to be adopted into both RFMO’s management measures.
WCPFC requires countries to, wherever possible, take measures necessary to prevent commercial transaction of Pacific bluefin tuna and its products that undermine the effectiveness of the management measures.

General tuna fishery measures implemented by both IATTC and WCPFC:
There is 100% observer coverage on large purse seiners (for WCPFC this is on the high seas, or on vessels fishing in multiple countries’ waters, or all vessels fishing between 20N and 20S).
Only 5% observer coverage is required on large longliners, considered too low for accurate data: a minimum of 20% coverage is recommended. In addition, data recorded by longliners in the IATTC area is considered inadequate for scientific purposes and minimum data standards must be identified and introduced.
To help address IUU, WCPFC and IATTC maintain an IUU Vessel List; a register of authorised large longliners; and prohibit transhipments at sea for large purse seiners, and most other transhipments must 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

Approximately 68% of Pacific bluefin is captured in purse seine fisheries that target free schooling fish, 9% by longlining, 5% by trolling and 11% by set nets. In the Eastern Pacific, most of the catches are transported to holding pens, where the fish are held for fattening and later sale to sashimi markets. These fisheries catch a very high proportion of juvenile fish (although recent juvenile fishing mortality has been lower than in previous years).

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 is also associated with bycatch of species such as sharks, turtles and marine mammals. Longlining targets larger, mature fish yet is often associated with the bycatch of vulnerable species such as seabirds, turtles and sharks. Whilst bycatch may comprise a small proportion of the total catch, the high volume of tuna that is caught means that it can still be significant for these vulnerable species.

To address this, both the IATTC and the WCPFC require a number of mitigation measures.
Purse seiners must not put out sets around whale sharks, turtles or cetaceans, and there are measures to limit the number of FADs and require their design to be non-entangling.
Seabirds: Longliners must use one or more seabird bycatch mitigation measures from a set list of options, depending on vessel size and fishing location, including weighted branch line, bird scaring lines, and night setting. However, recommended best practice is for those three measures to be applied simultaneously. A small area east of Tasmania and south of 40 degrees S is estimated to account for around 60% of the longline seabird bycatch south of 30 degrees S and 15% of the total seabird bycatch in the WCPFC Convention Area (this includes fleets targeting southern bluefin tuna as well as species managed by the WCPFC).
Turtles: The Eastern Pacific sub-population of leatherbacks is classified as Critically Endangered and at risk of extinction in the area, and is bycatch in longline and gillnet fisheries. Vessels must carry line cutters and de-hookers to promptly release turtles or to foster to recovery any sick or comatose turtles captured. Gear modifications such as circle hooks for shallow set gear, or in the IATTC the use of finfish bait only, are also required. A study in 2017 noted that less than 1% of Western and Central Pacific Ocean (WCPO) longline effort is subject to mitigation, even though approximately 20% of the WCPO longline effort consists of shallow sets. IATTC have noted that mortality rates of turtles due to longlining are possibly greater for those that set their lines at shallower depths at night for albacore and swordfish, although WCPFC notes that there are significantly more deep sets than shallow sets and a lower chance of live release from deep sets.
Sharks: permissible sharks are to be fully utilized and no more than 5% of fins to total shark weight can be retained; there is a prohibition to land oceanic whitetips and silky sharks (and mobula rays in IATTC area); and countries must develop national plans of action to address the bycatch of sharks, turtles and seabirds. Shark lines are prohibited. For the IATTC, any shark (whether alive or dead) caught that is not retained must be promptly released unharmed, following safe release requirements. There are special measures to protect silky sharks, including a limit on bycatch of silky sharks to a maximum of 20% of the total catch by fishing trip in weight. In 2016, WCPFC adopted 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. The scientific committee has noted that target and limit reference points have not yet been established for pelagic sharks by WCPFC. 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.
Monitoring and reporting is deficient in many fisheries, and the effectiveness of these measures has not been evaluated.
There is 100% observer coverage on large purse seiners in the IATTC area and parts of the WCPFC area, so the data coming from these fleets should be useful and of high quality. Only 5% observer coverage is required on longliners greater than 20m in length, although the scientific committee recommends 20% coverage and improved standards of data collection.

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].

Collette, B., Fox, W., Juan Jorda, M., Nelson, R., Pollard, D., Suzuki, N. & Teo, S., 2014. Thunnus orientalis. The IUCN Red List of Threatened Species 2014: e.T170341A65166749. Available at http://dx.doi.org/10.2305/IUCN.UK.2014-3.RLTS.T170341A65166749.en [Accessed on 10.12.2020].

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].

DiNardo, G., 2017. Summary report of the Pacific bluefin tuna international stakeholders meeting, hosted by the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean (ISC), 25-27 April 2017, Tokyo, Japan. 23pp. Available at http://isc.fra.go.jp/reports/isc/isc17_reports.html [Accessed on 13.11.2017].

IATTC, 2020. Inter-American Tropical Tuna Commission: Active IATTC and AIDCP Resolutions and Recommendations. Available at https://www.iattc.org/ResolutionsActiveENG.htm [Accessed on 14.12.2020].

IATTC, 2020. Report On The Tuna Fishery, Stocks, And Ecosystem In The Eastern Pacific Ocean In 2019. IATTC-95-05 presented to the Inter-American Tropical Tuna Commission 95th Meeting, 30 November - 4 December 2020, Online. Available at https://www.iattc.org/Meetings/Meetings2020/IATTC-95/Docs/_English/IATTC-95-05_The%20fishery%20and%20status%20of%20the%20stocks%202019.pdf [Accessed on 14.12.2020].

IATTC, 2020. Staff Recommendations for Management and Data Collection, 2020. IATTC-95-01 presented to the Inter-American Tropical Tuna Commission 95th Meeting, 30 November - 4 December 2020, Online. Available at https://www.iattc.org/Meetings/Meetings2020/IATTC-95/Docs/_English/IATTC-95-01-MTG_Conservation%20recommendations%20by%20the%20Commission%20staff.pdf [Accessed on 14.12.2020].

ISC, 2019. Report of the Nineteenth Meeting of the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean, 11-15 July 2019, Taipei City, Taiwan. Available at http://isc.fra.go.jp/pdf/ISC19/ISC19_PLENARY_Report_FINAL.pdf [Accessed on 29.11.2019].

ISSF, 2020. Status of the world fisheries for tuna. Nov. 2020. ISSF Technical Report 2020-16. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2020-16-status-of-the-world-fisheries-for-tuna-november-2020/ [Accessed on 10.12.2020].

ISC, 2020. Stock Assessment of Pacific Bluefin Tuna in the Pacific Ocean in 2020. ISC/20/ANNEX/11 presented to the 20th Meeting of the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean, July 15-20 2020, Online. Available at http://isc.fra.go.jp/pdf/ISC20/ISC20_ANNEX11_Stock_Assessment_Report_for_Pacific_Bluefin_Tuna.pdf [Accessed on 09.12.2020].

WCPFC, 2020. Compiled Information on Pacific Bluefin Tuna (Fishing Effort and Catch). WCPFC17-2020-IP071 presented to the 17th Regular Session of the WCPFC, 8 – 15 December 2020, Online. Available at https://www.wcpfc.int/node/49151 [Accessed on 10.12.2020].

WCPFC, 2020. Reference Document for the Review of CMM 2019-02 and Development of Harvest Strategies (Pacific Bluefin Tuna). WCPFC17-2020-18 presented to the 17th Regular Session of the WCPFC, 8 – 15 December 2020, Online. Available at https://www.wcpfc.int/node/48933 [Accessed on 10.12.2020].

WCPFC, 2020. Summary Report of the Sixteenth Regular Session of the Scientific Committee of the WCPFC, 12-19 August 2020 (Reconvened on 10 September 2020), Online. Available at https://www.wcpfc.int/file/568072/download?token=hcPeql6u [Accessed on 10.12.2020].

WCPFC, 2020. Conservation and Management Measures of the Western and Central Pacific Fisheries Commission. Compiled 2 Nov 2020 - 09:46. Available at https://www.wcpfc.int/system/files/booklets/31/CMM%20and%20Resolutions.pdf [Accessed on 10.12.2020].