Tuna, southern bluefin (Caught at sea)

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 (Caught at sea)

Sustainability rating five info

Sustainability overview

Updated: November 2019.

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. In 2011 the biomass of the spawning stock was estimated to be 5% of unfished levels. Despite recent improvements in management seeing the stock increase to 17%, it is still well below safe levels. The fishery overlaps with a number of endangered and critically endangered seabirds, notably albatross and petrel, which are caught as bycatch, 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

Stock Area

Southern Ocean

Stock information

The Southern bluefin tuna stock (SBT) is assessed and managed by the Commission for the Conservation of Southern Bluefin Tuna (CCSBT). This stock has been exploited for more than 50 years, with total catches peaking at 81,750 t in 1961. A 2006 review of data by the Commission indicated that catches during the 1980s and 1990s may have been substantially under-reported. A new stock assessment was carried out in 2017 and suggested that the spawning biomass was only 13% of its unfished state. However, this is an improvement on previous years: assessments indicated the stock was at 5% of its original biomass in 2011 and 9% in 2014. In 2019, the assessment was updated with the latest data, indicating that the stock is now 17% of unfished levels. This is an increase of 79% since 2009. Fishing mortality (F) in 2018 remains below the level associated with Maximum Sustainable Yield (F2018 at 0.55FMSY), but this is an increase from 2016, when F was 0.5MSY. The Spawning Stock Biomass (SSB) remains in an overfished state (SSB2018 is 0.64SSB MSY), but this is also an increase from 2016, when it was 0.49SSB MSY. Provisional 2017 catch is 13,947 t, similar to the 2016 catch of 14,445 t. The interim stock rebuilding objective, set in 2011, is to reach 20% of the unfished stock size by 2035 with 70% probability, and there is a limit below which the stock size should not be allowed to fall (SSB2010). There is a recent upward trend in the adult population which is a positive signal of rebuilding, recent recruitment is above the expected level (although more data is needed to model this accurately), and current levels of fishing mortality suggest future rebuilding will be faster than initially envisaged in 2011. There are suggestions that some relatively strong cohorts are moving through the fishery, though they have yet to contribute to the spawning stock. The next full stock assessment for southern bluefin tuna is scheduled to be conducted during 2020.

Southern bluefin tuna remains Critically Endangered on the IUCN Red List, but this is shortly to be reviewed by the IUCN SSC Tuna and Billfish Specialist Group.

Management

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). Roughly 60% of the catch is made in the Indian Ocean, 28% in the Pacific Ocean and 12% in the Atlantic Ocean. Owing to its high value, the stock has been considerably overfished and considerable under reporting of catches is thought to have occurred between 1986 and 2006.

The primary conservation measure for management of the southern bluefin tuna stock is the Total Allowable Catch (TAC), allocated to Japan and Australia - the two main fleets - as well as Republic of Korea, the Fishing Entity of Taiwan, New Zealand, Indonesia and 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 (which are set at 14,647t for 2015-2017, increasing to 17,647t for 2018-2020). The estimated total catch for the 2018 calendar year was 18224t, an increase of 3364t or 23% from the 2017 calendar year. When this is adjusted for carry over, reported catch was less than the TAC by 399t for the 2018 fishing season. These TACs are set in accordance with the long term management plan for the fishery, which aims to recover stocks to 20% of their unfished level by 2035 with 70% probability. 2017 projections suggest this might be achieved sooner, however there are concerns over levels of unaccounted mortality, e.g. through IUU, and there is no long term rebuilding target. While the scientific committee suggests that the current management plan does not need to be changed, in 2017 they recommended as a matter of urgency to take steps to quantify all sources of unaccounted mortality. A new management procedure will be developed to guide the setting of TACs for 2021 and onwards, taking into account changes in data availability.

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.

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

From 1952 - 2018, 77% of the reported Southern Bluefin Tuna catch was taken by longline and 23% using surface gears, primarily purse-seine and pole and line. On average, 78.7% of the SBT catch has been made in the Indian Ocean, 16.6% in the Pacific Ocean and 4.7% in the Atlantic Ocean. Current catches are around 18% of what they were at their peak in 1961.

Pelagic longlining targets large, mature fish, but encounters a relatively high proportion of bycatch of vulnerable species including large sharks, seabirds, marine turtles and other tuna and billfish. There is only one binding CCSBT measure relating to bycatch mitigation, which is to reduce seabird bycatch by requiring that Tori poles be used in all longline fisheries below 30 degrees south. There are other non-binding measures, and in 2018 CCSBT passed a resolution to align its measures with the measures of other RFMOs, although those measures can be inconsistent from one RFMO to the next and don’t necessarily follow best practice. The best practice approach is either the combined use of weighted branch lines, bird scaring (tori) lines and night setting or a hook-shielding device. Furthermore, the ability of CCSBT to enforce compliance is weak. 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. While there are no specific concerns about shark bycatch, there is not enough data to determine whether sharks need better protection. There is no fixed list of shark species affected by this fishery, preventing stock assessments from being carried out.

The purse seine component of the catch is usually made on younger fish which are then slowly towed 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.

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.

Alternatives

Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.

Anchovy, anchovies
Arctic char
Herring or sild
Mackerel
Salmon, Atlantic (Farmed)
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
Swordfish
Trout, Rainbow
Tuna, albacore
Tuna, skipjack
Tuna, yellowfin

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].

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].

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, 2018. Report of the Twenty Fifth Annual Meeting of the Commission for the Conservation of Southern Bluefin Tuna, 18 October 2018, Noumea, New Caledonia, 95 pp. Available at https://www.ccsbt.org/en/content/reports-past-meetings [Accessed on 04.12.2018].

CCSBT, 2019. Report of the Twenty Fourth Meeting of the Scientific Committee of the Commission for the Conservation of Southern Bluefin Tuna, 7 September 2019, Cape Town, South Africa, 121 pp. Available at https://www.ccsbt.org/sites/default/files/userfiles/file/docs_english/meetings/meeting_reports/ccsbt_26/report_of_SC24.pdf [Accessed on 26.11.2019].

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 http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T21858A9328286.en [Accessed on 26.11.2019].

ISSF, 2019. Status of the world fisheries for tuna. Oct. 2019. ISSF Technical Report 2019-12. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at https://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2019-12-status-of-the-world-fisheries-for-tuna-october-2019/ [Accessed on 26.11.2019].