Tuna, southern bluefin

Thunnus maccoyii

Method of production — Caught at sea
Capture method — All applicable methods
Capture area — Worldwide (FAO All Areas)
Stock area — Southern Ocean
Stock detail — All Areas
Picture of Tuna, southern bluefin

Sustainability rating five info

Sustainability overview

Updated: November 2020

Southern bluefin tuna have a low resilience to fishing pressure due to their longevity and late size at maturity. This is an extremely valuable species, with individual fish worth tens of thousands of pounds, which has led to heavy overfishing in the past. It is assessed as Critically Endangered by IUCN (International Union for the Conservation of Nature) and therefore receives a default red rating. It is still in a heavily overfished state, but is gradually recovering thanks the management measures in place to control the fishery. It is not subject to overfishing, and catches generally stay below the limits that have been set. The fishery overlaps with a number of endangered and critically endangered seabirds, notably albatross and petrel. There are concerning levels of bycatch of these species, especially in longline fisheries. The impact of the fishery on sharks is not well understood.

Biology

Tuna belong to the family Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Southern bluefin are found in temperate and cold seas of the southern hemisphere, but migrate to the tropics to spawn. They are a very large species, growing to 245cm in length and 260kg in weight, with a maximum age of 40 years. Southern bluefin mature between 8 -11 years of age (about 155cm in length). Young fish migrate seasonally between the south coast of Australia and the Indian Ocean. The only known spawning ground is in an area south-east of Java, Indonesia.

Stock information

Criterion score: Critical Fail info

Southern bluefin tuna remains Critically Endangered on the IUCN Red List. It is still in a heavily overfished state, but is gradually recovering thanks the management measures in place to control the fishery. It is not subject to overfishing.

The Southern bluefin tuna stock (SBT) is assessed and managed by the Commission for the Conservation of Southern Bluefin Tuna (CCSBT). Southern bluefin tuna has been fished since the 1940s. During that time, the stock has continuously declined, reaching a low of around 1% of its unfished level in 2009. Since then, it is estimated that the stock has been rebuilding at 5% per year. A new stock assessment was carried out in 2020 and estimated that the Total Reproductive Output (akin to Spawning Stock Biomass) of southern bluefin tuna had reached 20% of unfished levels. It has therefore reached its interim stock rebuilding objective, set in 2011, of 20% by the year 2035. The new rebuilding objective is now to reach 30% of unfished levels by 2035, which is the level associated with a Maximum Sustainable Yield (MSY), estimated to be 33,207 tonnes. For now, the stock remains in an overfished state, being at 69% of MSY. Fishing mortality (F) in 2020 is 52% of the level associated with MSY.

Stock projections indicate that SBT will reach 30% of unfished levels in 2037 if median catches are around 20,800t between 2020 and 2035. This is slightly behind target. The Total Allowable Catch for 2021-2023 was therefore kept at 17,647 tonnes per year - the same as for 2018-2020.

Fishing for juvenile SBT is common, especially by purse seiners, which then slowly tow the fish in large net pens back to the coast. Here, they are fattened for later sale on the sashimi market and individual fish can fetch upwards of GBP 100,000. While any reduction in fishing will increase the rate of stock rebuilding, the CCSBT scientific committee have noted that the benefits of reducing catches of juveniles could take around 8 years to show, because SBT are only fully mature around age 11.

MCS considers 20% of unfished levels to be equivalent to Blim. This means that while the increases in abundance are very encouraging, the stock is still at dangerously low levels and only just above Reduced Reproductive Capacity.

Management

Owing to its high value, southern bluefin tuna has been considerably overfished, but a rebuilding plan seems to have been effective and the stock is gradually recovering.

While southern bluefin ranges throughout the southern Atlantic, Pacific and Indian Oceans, the Regional Fisheries Management Organisations (RFMOs) for these oceans essentially defer management of the southern bluefin stock to the Commission for the Conservation of Southern Bluefin Tuna (CCSBT). The primary conservation measure for management of the southern bluefin tuna stock is the Total Allowable Catch (TAC), split between 7 countries. Roughly 1/3 each is allocated to Japan and Australia, 7% each to the Republic of Korea and Taiwan, 6% each to New Zealand and Indonesia, and 2% to South Africa. Some flexibility is provided for limited carry-forward of unfished allocations between quota years. In recent years, reported catches have been below the TACs. The estimated total catch for 2019 was 16,843t. TACs were set at 17,647t for 2018-2020 and have been kept at the same level for 2021-2023. These TACs are set in accordance with the long term management plan for the fishery. A new stock assessment was carried out in 2020 and estimated that the Total Reproductive Output (akin to Spawning Stock Biomass) of southern bluefin tuna had reached 20% of unfished levels. It has therefore reached its interim stock rebuilding objective, set in 2011, of 20% by the year 2035. The new rebuilding objective is now to reach 30% of unfished levels by 2035, which is the level associated with a Maximum Sustainable Yield (MSY), estimated to be 33,207 tonnes. Stock projections indicate that SBT will reach 30% of unfished levels in 2037 if median catches are around 20,800t from 2020 to 2035. This is slightly behind target and is the reason that the 2021-2023 TAC was kept at the same level as the previous year. It is positive to see this precautionary approach to managing a stock that is still at very low levels.

The CCSBT has a Catch Documentation Scheme (CDS) for southern bluefin tuna, providing for tracking and validation of legitimate products from catch to the point of first sale on domestic or export markets. All southern bluefin tuna products must be accompanied by documentation which includes details of the vessel and area of catch, which will help monitor catches and trade. In addition, the CCSBT have developed a register of vessels that are authorized to catch southern bluefin tuna, so that members and cooperating non-members of the CCSBT are required to refuse the import of this species caught by vessels not on the list, as well as an annually-reviewed register of vessels carrying out Illegal, Unreported and Unregulated (IUU) fishing. All transhipments must be authorised in advance and Observed. In 2016, the Commission banned the use of large-scale driftnets on the high seas where it might lead to catches of southern bluefin tuna.

There are some compliance concerns in this fishery. Indonesia exceeded its catch allowance in 2019 and 2020 by 232 tonnes as of October 2020, potentially rising to 950 tonnes by the end of the season. It is not appropriately controlling catches by its fishery, but has agreed pay back its over catches gradually from 2022 to 2026, and to ensure that 2021 catch is in line with agreed limits. There are also catch documentation issues for South Africa.

As the fishery operates within the jurisdiction of other RFMOs, vessels are also expected to adhere to the management and conservation measures of these intergovernmental organisations. CCSBT works to ensure its own regulations are compatible with those of other RFMOs.

Capture Information

Around two-thirds of southern bluefin tuna catch is taken by longlining, which can cause the bycatch of vulnerable species including a number of endangered seabird species. Purse-seine is responsible most of the rest, with some caught by pole and line. Purse seining can have some bycatch issues, although is less of a concern than longlining. Pole and line is a relatively low-impact method, although it does use other fish species for bait. In 2020, the CCSBT noted that there were continued high levels of seabird and shark bycatch, despite adherence by some Members to agreed mitigation methods. There are significant concerns about the bycatch of endangered seabird species.

Pelagic longlining encounters a relatively high proportion of bycatch of vulnerable species including large sharks, seabirds, marine turtles and other tuna and billfish. CCSBT has only one legally-binding measure to reduce catches of seabirds: Tori poles (bird scarers) must used in all longline fisheries south of 30 degrees south. In addition, it is recommended that countries adopt the International Plan of Action for Reducing Incidental Catches of Seabirds in Longline Fisheries (IPOA-Seabirds), the International Plan of Action for the Conservation and Management of Sharks (IPOA-Sharks), and the FAO Guidelines to reduce sea turtle mortality in fishing operations (FAO-Sea turtles), if they have not already done so. In 2018 CCSBT passed a resolution requiring all SBT vessels to comply with the ecologically-related-species measures of the relevant tuna RFMOs for the area where they are fishing. On average, 78.7% of the SBT catch is from the Indian Ocean, 16.6% from the Pacific, and 4.7% from the Atlantic. Vessels must therefore comply with the measures of one of three tuna commissions (IOTC, WCPFC, and ICCAT). However, these RFMOs don’t necessarily follow best practice in their regulations. For seabirds, this is either a hook-shielding device, or the combined use of weighted fishing lines, bird scaring (tori) lines and night-setting. Bycatch of seabirds is of serious concern, having remained high for several years, but a proposed binding resolution in 2017 could not be agreed upon. A 2016 risk assessment found that of 25 albatross and petrel species in the area, 9 were caught as incidental bycatch in surface longline fisheries at levels that exceeded their population productivity. In 2020, ACAP (the Agreement on the Conservation of Albatrosses and Petrels) identified non-compliance in the proper use of seabird bycatch mitigation measures adopted by tuna RFMOs, including the CCSBT, as a critical issue.

With regard to sharks, bycatch is of concern but there is not enough data to determine whether better protection is needed. There is no fixed list of shark species affected by this fishery, preventing stock assessments from being carried out.

There is a ban on the use of large-scale driftnets on the High Seas in a manner which can reasonably be expected to result in the catching, taking or harvesting of southern bluefin tuna.

In 2017 CCSBT agreed to examine standards for electronic monitoring programs on vessels fishing for southern bluefin, to support observer programmes. There is a target level of 10% observer coverage of catch and effort, but compliance with this is patchy and it has been suggested that a target of 20% on longliners would be more appropriate. Some countries have said that low observer coverage makes it more difficult for them to identify and tackle non-compliance in their own fleets.

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 25.11.2020].

CCSBT, 2017. Report of The Twelfth Meeting of the Ecologically Related Species Working Group for the Commission for the Conservation of Southern Bluefin Tuna, 21-24 March 2017, Wellington, New Zealand. 42 pp. Available at https://www.ccsbt.org/en/content/reports-past-meetings [Accessed on 10.12.2018].

CCSBT, 2020. Report of the Twenty Fifth Meeting of the Scientific Committee of the Commission for the Conservation of Southern Bluefin Tuna, 7 September 2020, Online, 142 pp. Available at https://www.ccsbt.org/sites/default/files/userfiles/file/docs_english/meetings/meeting_reports/ccsbt_27/report_of_SC25.pdf [Accessed on 25.11.2020].

CCSBT, 2020. Report of the Twenty Seventh Annual Meeting of the Commission for the Conservation of Southern Bluefin Tuna, 16 October 2020, Online, 101 pp. Available at https://www.ccsbt.org/sites/default/files/userfiles/file/docs_english/meetings/meeting_reports/ccsbt_27/report_of_CCSBT27.pdf [Accessed on 25.11.2020].

CCSBT, 2020. Operational Resolutions and Other Important Documents. Available at https://www.ccsbt.org/en/content/operational-resolutions-and-other-important-documents [Accessed on 25.11.2020].

Collette, B., Chang, S.-K., Di Natale, A., Fox, W., Juan Jorda, M., Miyabe, N., Nelson, R., Uozumi, Y. & Wang, S. 2011. Thunnus maccoyii. The IUCN Red List of Threatened Species 2011: e.T21858A9328286. Available at https://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T21858A9328286.en. [Accessed on 25.11.2020].

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].

ISSF, 2020. Status of the world fisheries for tuna: March 2020. ISSF Technical Report 2020-12. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2020-12-status-of-the-world-fisheries-for-tuna-march-2020 [Accessed on 25.11.2020].