Tuna, Atlantic bluefin (Caught at sea)

Thunnus thynnus

Method of production — Caught at sea
Capture method — All applicable methods
Capture area — North East Atlantic (FAO 27) and Mediterranean & Black Sea (FAO 37)
Stock area — East Atlantic & Mediterranean
Stock detail

All Areas


Picture of Tuna, Atlantic bluefin (Caught at sea)

Sustainability rating rating under review info

Sustainability overview

Atlantic bluefin tuna is a large, slow growing and long lived species, making it vulnerable to overfishing. The stock has been significantly overfished since the 1970s, and illegal, unreported and unregulated (IUU) fishing has been a serious problem as individual fish can regularly be sold in excess of tens of thousands of pounds. Substantial improvements in stock management, monitoring and enforcement under a recovery plan have had a positive effect on the stock. A new stock assessment was carried out in 2017 and whilst is considered to be more reliable than previous assessments, the status of the stock is still not clear. The results indicate that fishing mortality is well below the Maximum Sustainable Yield (F approximately at 0.34Fmsy proxy) yet the modelled state of the biomass is highly dependent on the historical productivity of the stock. Scenarios suggest that the stock is no longer overfished under medium and low recruitment levels, but remains overfished under the high recruitment scenario. The state of the biomass is therefore unknown. The East Atlantic component of the stock is likely important to the West Atlantic bluefin stock and the species remains listed as Endangered by the IUCN Globally and in the Mediterranean, and Near Threatened in Europe.

MCS is currently reviewing this assessment and welcomes contributions from stakeholders with good insight and knowledge of this fishery.

Biology

Tuna belong to the family Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Able to tolerate both warm and cool temperatures, bluefin tuna range throughout the entire north Atlantic and adjacent seas, (primarily the Mediterranean Sea) and can frequent depths to 1000m. Despite this thermal tolerance, a recent analysis of present vs. historical ranges concluded that Atlantic bluefin tuna has shown range contractions of 46% since 1960 ? more than any other pelagic species . Despite poorly understood movements from east to west, a distinction in populations is made between the two regions. Interestingly, life history characteristics differ greatly between them. In the Mediterranean, bluefin tuna is assumed to mature at approximately 25 kg (age 4), whereas in the Gulf of Mexico in the West Atlantic, maturity occurs at approximately 145 kg (age 9). Northern bluefin grow slowly compared with other tunas and billfish but can reach more than 450cm in length and 680kg in weight with a maximum age of approximately 40 years. Spawning occurs from April to June in the Gulf of Mexico and June to August in the Mediterranean.

Stock information

Stock Area

East Atlantic & Mediterranean

Stock information

The bluefin tuna stock in the East Atlantic and Mediterranean are assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catches in the East Atlantic and Mediterranean reached an estimated peak of 61,000 t in 2007, severely overfishing the stock. Catches were seriously under-reported between 1998 and 2007, and it is estimated that realized catch during this period was around 50,000 t to 61,000 t per year. The introduction of fattening and farming activities into the Mediterranean in 1997 and good market conditions resulted in rapid changes in the Mediterranean fisheries for bluefin tuna, mainly due to increasing purse seine catches. From 2007 to 2011, reported catches steadily decreased to 11,781 t, and subsequently steadily increased to the provisional 2017 catch of 23,616 t (just above the Total Allowable Catch (TACs) of 23,155 t).

The latest stock assessment was carried out in 2017 and is considered to be more reliable than previous assessments. There have been considerable improvements in the data quality and quantity over the past few years, but there remain gaps in the data for several fisheries prior to 2014, especially in the Mediterranean. The Scientific Committee does not expect that there can be further improvement in historical statistics. The current assessment uses the estimated catches from 1996-2007 rather than the declared ones. It was not possible to calculate biomass-based reference points (e.g. MSY and FMSY) in the latest assessment and in the absence of such knowledge, a fishing-effort-based (F) proxy has been used for the Eastern stock since 2008. The results indicate that fishing mortality is well below the Maximum Sustainable Yield (F approximately at 0.34Fmsy proxy). The modelled state of the biomass is highly dependent on the historical productivity of the stock. Scenarios suggest that the stock is no longer overfished under medium and low recruitment levels, but remains overfished under the high recruitment scenario. The state of the biomass is therefore unknown.

Projections indicate that annual constant catches of up to 36,000 t have higher than 60% probability of maintaining fishing effort at sustainable levels, and catches of 28,000 t or less have a higher than 50% probability of allowing a continued increase in the stock.

It still remains unclear how much of the Eastern Atlantic stock mixes with and supports the Western Atlantic stock. The species is listed as Endangered by the International Union for the Conservation of Nature (IUCN) Globally and in the Mediterranean (2011) and listed as Near Threatened in Europe (2015), yet as the stock status has rapidly changed, there is a need to update these assessments.

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 address this, Intergovernmental Regional Fisheries Management Organisations (RFMOs) have been established. There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. This stock is managed and assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). 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. There remain large data deficiencies in most tuna and billfish fisheries, particularly with regards to fine scale spatial and temporal data for both target and especially for vulnerable bycatch species. For this reason, it is important to choose tuna that has been caught by vessels that are well regulated by their flag state.

There is a 15-year recovery plan for Eastern and Mediterranean bluefin, starting in 2007 and continuing to 2022, which is on track to achieve its target of Bmsy with at least 60% probability. The combination of size limits and the reduction of catch has certainly contributed to a rapid increase of the abundance of the stock. Given this increase, the scientific committee advises moving from the current rebuilding plan to a management plan.
TACs (Total Allowable Catches) have increased from 16,142 t in 2015 to 23,155 t in 2017, and continue to increase: 28,200 t for 2018; 32,240 t for 2019; and 36,000 t for 2020. Whilst this has largely been in line with scientific advice, constant annual catches over approximately 32,000 t are projected to lead to a reduction biomass. Individual catch limits are assigned to each country. Countries must submit fishing plans, establishing quotas for each type of fishing gear. Unlike for other stocks, no carry-over of quota from one year to the next is allowed. Bluefin caught as bycatch cannot exceed 5% of the total catch of a vessel and must form part of the overall quota.
To protect spawning grounds (the precise location of which are still being identified), open seasons are set for defined periods and these windows vary depending on gear and location: Longliners over 24m may fish for this species for a 5 or 6 month period, depending on location. Purse seiners may fish for 1 or 4 months, depending on location. Bait boats and trolls, pelagic trawlers, and sport & recreational boats may fish for 4 months. Other gear is prohibited.
Aerial vehicles can not be used to help vessels find bluefin tuna.
Bluefin below 30kg or 115cm may not be caught, with a few exceptions.
Sport & recreational vessels are limited to 1 bluefin per day.
Capacity is limited, and countries must submit management plans to demonstrate how they will meet this requirement. The number and tonnage of vessels fishing for bluefin is limited to that of 2007/8, although the number of purse seiners is limited to numbers from 2013 or 2014. The number of traps is limited to that of 2008. Farming capacity is limited to that of 2008, and input of fish into farms is limited to that of any one year from 2005-2008.
Countries must keep a list of vessels and traps authorised to fish for, and facilities authorised to farm, this species.
Transhipment at sea is prohibited, and may only take place in designated ports with prior authorisation.
Vessels over 24m must have Vessel Monitoring Systems. Minimum observer coverage is higher than for other stocks and varies by gear: 20% for longliners, pelagic trawlers, and bait boats over 15m; 100% of purse seiners, towing vessels, and harvesting operations from traps.

There is a catch documentation scheme which from 2018 will be fully electronic to improve tracking of bluefin from catch to farm to export.

Other measures for bluefin include:
As of 2006, catch of Atlantic bluefin by longliners from the central Atlantic is frozen to levels caught in 1999/2000 as mixing of eastern and western stocks in this area is not well understood.
Countries must carry out research to support better understanding of the species.

Capture Information

Approximately 61% of the catch is made by purse seiners that set on free schools (as opposed to using Fish Aggregation Devices, FADs). These fish are live captured to then be transported to sea pens where they are held and fattened for later sale on the Asian sashimi market. Purse seining on free schools encounters less bycatch compared with FAD associated fisheries, though both still have interactions with vulnerable species.

15% of the catch is made by longlining, a method associated with the bycatch of vulnerable species, including sharks, sea turtles and seabirds.

17% of the catch is made by fixed traps that have minor impact on sensitive species.

3% of the catch is made by pole-and-line fisheries. This is a very selective method of fishing yet relies on significant amounts of baitfish. Assessment of these bait fish fisheries is generally needed.

2% is also taken in recreational sports fisheries.

To a lesser extent, bluefin is also captured in illegal gill net fisheries. For EU Member States, driftnet fishing for tuna has been banned since January 2002, yet remains a problem in some Italian fisheries and is still officially permitted in Morocco. Gill netting, especially offshore drift netting, encounters a very high proportion of bycatch.

ICCAT aims to take an ecosystem-based and precautionary approach to fisheries management. In order to minimize the ecological impact of FADs, in particular the entanglement of sharks, turtles and other non-targeted species, and the release of synthetic persistent marine debris, countries must use non-entangling FADs and phase out non-biodegradable FADs. Countries must have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem. In order to protect juvenile swordfish, a closure period applies to longline vessels targeting Mediterranean albacore from 1 October to 30 November each year.

For sharks: Countries are required to develop and submit National Plans of Action for the conservation and management of sharks. Sharks must be fully utilised (e.g. no removal of fins). Sharks must be released wherever possible (if not being directly targeted) and countries must try to minimise bycatch of sharks (although no gear-specific measures are identified). Catching silky sharks, hammerheads, oceanic whitetips, and bigeye threshers is prohibited, and catching other thresher species is discouraged. Shortfin mako can be caught and retained, but as of 2017 the country’s law must require a minimum length of 180cm for males and 210cm for females, otherwise, shortfin makos caught alive must be released unharmed. This is expected to prevent the stock’s currently poor state from worsening, and a rebuilding plan will be developed for 2019. In 2016 additional measures for blue shark were introduced, mainly focussed on improved data recording, with potential to introduce Harvest Control Rules. A catch limit of 39,102 t was also introduced in the north Atlantic (but none for the south Atlantic): if exceeded the commission has committed to reviewing the effectiveness of its blue shark management measures. Preliminary catch in 2016 was 42,117 t. Porbeagle is overfished throughout the Atlantic, significantly so in the northwest, and for the north Atlantic overall it is predicted to take at least 30 years to recover if there was zero fishing mortality. The main porbeagle-directed fisheries (EU, Uruguay and Canada) have closed, and ICCAT have a recommendation to release live porbeagle unharmed, but it is still caught incidentally and discarded, and also landed by other fleets. Currently there is not enough data to properly assess the status of many pelagic sharks (no assessments have been carried out for the Mediterranean) and more work is needed to understand the effects of entanglement in FADs.

For seabirds: There are particular concerns over the status of albatross and petrels. South of 20 degrees South, vessels must use bird-scaring lines. Swordfish vessels are exempt from this if they fish at night and weight their hooks. South of 25 degrees South, vessels must use 2 of the three measures mentioned. In the Mediterranean, these measures are voluntary. However, recommended best practice is to use all three of the aforementioned measures for all longline vessels.

For turtles: Purse seiners must avoid encircling turtles and release them when they do so. Longliners must carry equipment and have training to enable them to safely release turtles that have been caught. Countries are required to research and trial circle hooks for longliners. The scientific committee recommends that longliners targeting swordfish and sharks must use either large circle hooks or finfish bait as mitigation, but this has not been implemented.

Minimum observer coverage is higher than for other stocks and varies by gear: 20% for longliners, pelagic trawlers, and bait boats over 15m; 100% of purse seiners, towing vessels, and harvesting operations from traps.

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
Salmon, Atlantic (Farmed)
Salmon, Chinook, King Salmon
Salmon, Chum, Keta, Calico or Dog salmon
Salmon, Coho , Silver, White
Salmon, Pink, Spring , humpback
Salmon, Sockeye , Red Salmon, Bluebacks, Redfish
Sprat, whitebait
Swordfish
Trout, Rainbow
Tuna, albacore
Tuna, bigeye
Tuna, skipjack
Tuna, yellowfin

References

Collette, B., Amorim, A.F., Boustany, A., Carpenter, K.E., de Oliveira Leite Jr., N., Di Natale, A., Die, D., Fox, W., Fredou, F.L., Graves, J., Viera Hazin, F.H., Hinton, M., Juan Jorda, M., Kada, O., Minte Vera, C., Miyabe, N., Nelson, R., Oxenford, H., Pollard, D., Restrepo, V., Schratwieser, J., Teixeira Lessa, R.P., Pires Ferreira Travassos, P.E. & Uozumi, Y. 2011. Thunnus thynnus. The IUCN Red List of Threatened Species 2011: e.T21860A9331546. Available at http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T21860A9331546.en [Accessed on 11.12.2018].

Froese, R. and D. Pauly. Editors. 2018. FishBase version (06/2018). Available at www.fishbase.org [Accessed on 10.12.2018].

ICCAT, 2017. Report of the 2017 ICCAT bluefin stock assessment meeting for the International Commission for the Conservation of Atlantic Tunas, 20-28 July 2017, Madrid, Spain. 106 pp. Available at http://www.iccat.int/com2017 [Accessed on 27.11.2017].

ICCAT, 2018. Report of the Standing Committee on Research and Statistics (SCRS) of the International Commission for the Conservation of Atlantic Tunas, 1-5 October 2018, Madrid, Spain. 469 pp. Available at https://www.iccat.int/Documents/Meetings/Docs/2018/REPORTS/2018_SCRS_REP_ENG.pdf [Accessed on 22.11.2018].

ICCAT, 2018. Resolutions, Recommendations and other Decisions. Available at http://www.iccat.es/en/RecsRegs.asp [Accessed on 11.12.2018].

IPNLF, 2012. Ensuring sustainability of live bait fish, International Pole and Line Foundation, London, 57 pp.

ISSF, 2018. Status of the world fisheries for tuna: October 2018. ISSF Technical Report 2018-21. International Seafood Sustainability Foundation, Washington, D.C., USA. 103 pp. Available at: https://iss-foundation.org/about-tuna/status-of-the-stocks/ [Accessed on 06.12.2018].