Tuna, yellowfin

Thunnus albacares

Method of production — Caught at sea
Capture method — Longline
Capture area — Atlantic Ocean (FAO 21,27,31,34,41 and 47)
Stock area — Atlantic
Stock detail — All Areas
Picture of Tuna, yellowfin

Sustainability rating three info

Sustainability overview

Updated: November 2020

Atlantic yellowfin tuna is not overfished and is not subject to overfishing. However, there is some uncertainty in this assessment, and recent catches have been above recommended levels, which could cause the stock to decline. Biomass has continuously declined throughout the lifetime of the fishery, while fishing mortality has been increasing since the mid-2000s. The main management measures are catch limits and a reduction in the use of Fish Aggregating Devices (FADs). The catch limits have been exceeded in every year since 2015, at levels that are expected to cause the stock to decline. Existing management is therefore not effective at controlling fishing pressure on this stock. The FAD limits are intended to reduce catches of juvenile yellowfin, but didn’t work. Measures were strengthened in 2019, but it is too early to tell if this will be effective. Longline catches for yellowfin in the Atlantic have fluctuated since the 90s, but now account for about 12% of the total catch (around 16,000 tonnes in 2019). While longlining is unlikely to have habitat impacts, it can have a bycatch of highly vulnerable species such as sharks, turtles, and seabirds. ICCAT states that it aims to take an ecosystem-based and precautionary approach to fisheries management, but a number of shark species remain heavily overfished. Of particular concern is the shortfin mako, which can still be legally caught despite populations being at very low levels. Scientifically recommended gear modifications for longliners, which would reduce bycatch and mortality of vulnerable species, have not been implemented.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to ensure the TAC is not exceeded. Large buyers should consider supporting such improvements.

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

Criterion score: 0 info

Atlantic yellowfin tuna is not overfished and is not subject to overfishing. However, there is some uncertainty in this assessment, and recent catches have been above recommended levels, which could cause the stock to decline. Biomass has continuously declined throughout the lifetime of the fishery, while fishing mortality has been increasing since the mid-2000s.

Yellowfin stocks in the Atlantic are assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). The last stock assessment was carried out in 2019, using data up to 2017. Catches of yellowfin declined from their peak of 190,000t tonnes in 1990 to 100,000t in 2007, subsequently rising to an average of 136,000 tonnes from 2015-2019. Biomass has continuously declined throughout the lifetime of the fishery, including between 2014 and 2018, while fishing mortality has been increasing since the mid-2000s. In 2018, biomass (B) was 117% of levels associated with Maximum Sustainable Yield (MSY) and fishing mortality (F) was just below MSY, at 96%. This is an improvement from the previous assessment, which indicated that the stock was in an overfished state. However, this is not owing to stock recovery, but because of improved data in the model. The 2019 stock assessment has a high level of uncertainty.

The preliminary catch in 2019 was 132,158 tonnes. Projections indicate that catch levels at or below 120,000t (the estimated Maximum Sustainable Yield) would maintain healthy biomass through to 2033. However, the most recent catch estimates suggest that overall catches have exceeded 120,000 t every year since 2015, and if this continues the stock will decline. If catches remain around 140,000 tonnes, there is only a 20% probability that the stock will be above BMSY and below FMSY by 2030. Given that this is also in excess of Total Allowable Catch (110,000t), existing conservation and management measures appear to be insufficient, and the scientific committee recommends that they be strengthened.

Most catches are from the east Atlantic purse seine fishery, about a third of which is on Fish Aggregating Devices (FADs). FADs tend to have a higher catch of juveniles than FAD-free purse seining on free-swimming schools of tuna. The scientific committee has highlighted that increased catches of small yellowfin (and small bigeye, as they are caught together on FADs) will have negative effects on stock size and future harvest rates. Therefore, effective measures should be introduced to reduce fishing mortality on small yellowfin and bigeye tunas.

In the previous assessment, there were uncertainties in stock structure, natural mortality, and growth. As hoped, the ongoing Atlantic Ocean Tropical Tuna Tagging Programme (AOTTP) and Pacific yellowfin tagging studies were able to provide data to address a number of these uncertainties, highlighting the value of tagging programmes for managing tuna fisheries.

Management

Criterion score: 0.75 info

The main management measures for Atlantic yellowfin are catch limits and a reduction in the use of Fish Aggregating Devices (FADs). The catch limits have been exceeded in every year since 2015, at levels that are expected to cause the stock to decline. Existing management is therefore not effective at controlling fishing pressure on this stock. The FAD limits are intended to reduce catches of juvenile yellowfin, but didn’t work. Measures were strengthened in 2019, but it is too early to tell if this will be effective.

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.

The TAC (Total Allowable Catch) for yellowfin from 2012 onwards is 110,000 t, and keeping catches at 120,000t or less is expected to maintain healthy stock status through to 2033. However, the preliminary catch in 2019 was 132,158 tonnes, and overall catches have exceeded 120,000 t every year since 2015. The level by which the TAC has been exceeded ranges from 17-37%, and if this level of fishing pressure is maintained the stock is projected to decline. If catches remain around 140,000 tonnes, there is only a 20% probability that the stock will be above BMSY and below FMSY by 2030. Given that this is also in excess of Total Allowable Catch (110,000t), in 2018 and again in 2019 the scientific committee suggested that existing conservation and management measures appeared to be insufficient and needed to be strengthened.

The main other management measures for bigeye, skipjack and yellowfin, which are usually caught together, include:

There is a tagging programme to improve stock assessments for tropical tunas and gauge effectiveness of management measures for these species. This helped to improve the quality of the 2019 yellowfin assessment. In 2017 ICCAT banned the discarding of skipjack, yellowfin and bigeye, so that all fish caught must now be landed.

There is concern about the impact of catching tuna using purse seine nets around fish aggregation devices (FADs). The increasing use of FADs in skipjack fisheries since the early 1990s has changed the species composition of free schools. It is noted that, in fact, free schools of mixed species were considerably more common prior to the introduction of FADs. It may also have negative consequences for adult yellowfin and bigeye tuna, as well as other by-catch species. Association with FADs may also have an impact on the biology (growth rate, plumpness of the fish) and on the ecology (distances, movement orientation) of skipjack and yellowfin (the “ecological trap” concept). Many juvenile fish are often caught in purse seine fisheries, mainly skipjack, yellowfin and bigeye. When a high proportion of young fish are removed from a population, the potential maximum catch from a fishery is reduced. The recent average weight in European purse seine catches, which represent the majority of the landings, has declined to about half of the average weight of 1990, at least in part due to the use of FADs and the increased catches of small yellowfin. A decline in average weight and size is also evident in eastern tropical bait boat catches, although longline catches have not seen the same trend. In 2015 a working group was formed to look at ways to reduce juvenile catches of bigeye and yellowfin tuna caught in FAD fishing, and countries must have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem. However, the scientific committee continues to recommend that more work needs to be done on this.

A multi-annual management programme has been in place for bigeye and yellowfin since 2012, and eastern skipjack since 2015, mostly focussed on FAD management. Fishing for these species using aggregation devices, including FADs, was prohibited from 1st January to 28th February in an area off the west African coast to reduce catches of juvenile bigeye and yellowfin, for the rest of the year vessels were limited to 500 FADs. This failed to reduce the mortality of juvenile bigeye and yellowfin tuna so in 2019, to address this, the number of FADs was reduced from 500 to 350 in 2020 and 300 in 2021. The FAD closure was extended to the full convention area, lasting 2 months in 2020 and 3 months in 2021. In 2020 the scientific committee advised that it was too soon to evaluate the impact of these changes.

Other management by ICCAT includes:
ICCAT maintains a list of vessels over 20m authorised to fish for this species, although other vessels may retain them as bycatch as long as the country sets limits on this and doesn’t exceed its quota.
In 2019 ICCAT increased observer coverage: large purse seiners targeting tropical tunas must have 100% coverage year round rather than just during the FAD closures, and longline coverage will increase from 5% to 10% in 2022. However, the 5% coverage was not well complied with or enforced by some fleets (although others exceeded it), and even this increase falls short of recommendations for a minimum of 20% for accurate reporting of bycatch. However, standards for electronic monitoring are to be developed by 2021. Purse seine and longline vessels over 20m long are encouraged to increase their observer coverage from the required minimum, and some have. Vessel Monitoring Systems are required for all vessels over 24m.
Drift nets were banned by the EU in 2002 and by ICCAT in the Mediterranean in 2003.
In terms of enforcement and compliance with management measures: in 2016 ICCAT passed measures to strengthen and streamline its compliance assessment process and to develop a scheme of responses to non-compliance. There is also a list of vessels authorised to fish for tuna and tuna-like species in the ICCAT area, and a list of vessels caught carrying out Illegal, Unreported or Unregulated activities. At-sea transhipment is prohibited unless pre-authorised and the vessel has an observer on board.

Capture Information

Criterion score: 0.75 info

Longline catches for yellowfin in the Atlantic have fluctuated since the 90s, but now account for about 12% of the total catch (around 16,000 tonnes in 2019). While longlining is unlikely to have habitat impacts, it can have a bycatch of highly vulnerable species such as sharks, turtles, and seabirds. ICCAT states that it aims to take an ecosystem-based and precautionary approach to fisheries management, but a number of shark species remain heavily overfished. Of particular concern is the shortfin mako, which can still be legally caught despite populations being at very low levels. Scientifically recommended gear modifications for longliners, which would reduce bycatch and mortality of vulnerable species, have not been implemented.

Management in place to protect vulnerable species include:

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); must be released wherever possible (if not being directly targeted); and countries must try to minimise bycatch of sharks. No gear-specific measures are identified, despite repeated recommendations from the scientific committee to use circle hooks, which have been shown to increase survival of shortfin mako, blue marlin and swordfish if accidentally caught. Catching silky sharks, hammerheads, oceanic whitetips, and bigeye threshers is prohibited, and catching other thresher species is discouraged. Shortfin mako, which is heavily overfished, can be caught and retained if over 180cm for males and 210cm for females, otherwise, they must be released unharmed. An updated assessment in 2019 indicated that shortfin mako is unlikely to recover to healthy levels until 2070, unless size restrictions combined with a fixed Total Allowable Catch were introduced. The maximum catch that would allow recovery by 2070 with a reasonable probability (60%) was 300 tonnes. Regardless of management measures, the stock will continue to decline until 2035. However, in 2019 ICCAT failed to reach agreement on measures to protect this species. For blue shark, catch limits are now in place for both northern (39,102t as of 2016) and southern (28,923t as of 2016) stocks, with the northern TAC being allocated to countries - a first for ICCAT shark stocks. If exceeded, the commission has committed to reviewing the effectiveness of its blue shark management measures, although preliminary catch of northern blue shark in 2016 was 42,117 t. Porbeagle is significantly so in the northwest Atlantic and stock status in the northeast and south Atlantic is unknown. In the northwest, the stock could recover by 2035 under recent catches, but these are likely to be underestimated because dead discards are rarely reported. 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.

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 (bird-scarers, night fishing or weighted hooks). 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: 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 as of 2019 this has still not been implemented. The scientific committee has noted that management or turtle bycatch is only in place for purse seine and longline. Measures for other gears are needed to both coordinate methods to avoid them, and to improve data on bycatch.

For marine mammals: there are no specific management measures to protect marine mammals, including cetaceans. ICCAT has not prioritised collecting data on mammal bycatch to date. More needs to be done to understand and reduce the impact of ICCAT fisheries on marine mammals.

Observer coverage is only 5%, and many fleets might not even reach this level, although others are at 100% of fishing trips. Scientific recommendations are for at least 20% for accurate reporting of bycatch.

References

EC, 2019. European Commission Press: Good news for tuna and blue sharks, 29.11.2019. Available at https://ec.europa.eu/fisheries/press/good-news-tuna-and-blue-sharks_en [Accessed on 09.12.2019].

ICCAT, 2019. Report of the 2019 ICCAT yellowfin tuna stock assessment meeting, 8-16 July 2019, Grand-Bassam, Cote d'Ivoire. Available at https://www.iccat.int/Documents/SCRS/DetRep/YFT_SA_ENG.pdf [Accessed on 09.12.2019].

ICCAT, 2019. Report of the Standing Committee on Research and Statistics (SCRS) of the International Commission for the Conservation of Atlantic Tunas, 30 September - 4 October 2019, Madrid, Spain. 459 pp. Available at https://www.iccat.int/Documents/Meetings/Docs/2019/REPORTS/2019_SCRS_ENG.pdf [Accessed on 09.12.2019].

ICCAT, 2020. Resolutions, Recommendations and other Decisions. Available at http://www.iccat.es/en/RecsRegs.asp [Accessed on 26.11.2020].

ICCAT, 2020. 2020 SCRS Advice to the Commission, September 2020, Madrid, Spain. 362pp. Available at https://www.iccat.int/Documents/SCRS/SCRS_2020_Advice_ENG.pdf [Accessed on 26.11.2020].

ICCAT, 2020. Report of the 2020 ICCAT Intersessional Meeting of the Sub-Committee on Ecosystems, 4-6 May 2020, Online. 28pp. Available at https://iccat.int/Documents/Meetings/Docs/2020/REPORTS/2020_SC_ECO_ENG.pdf [Accessed on 26.11.2020].

ISSF, 2019. International Seafood Sustainability Foundation Blog: ICCAT Moves to Protect Atlantic Bigeye and Close Gaps in Monitoring and Data Collection, 4 December 2019. Available at https://iss-foundation.org/iccat-moves-to-protect-atlantic-bigeye-and-close-gaps-in-monitoring-and-data-collection/ [Accessed on 09.12.2019].

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].

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

ISSF, IPNLF, 2019. Skippers’ Guidebook to Pole-and-Line Fishing Best Practices. Version 1.0 - April 2019. International Seafood Sustainability Foundation and International Pole & Line Foundation. Available at http://ipnlf.org/perch/resources/pl-guidebookipnlfissffinal.pdf [Accessed on 30.11.2020].

Restrepo, V., Dagorn, L., Itano D., Justel-Rubio A., Forget F. and Moreno, G., 2017. A summary of bycatch issues and ISSF mitigation initiatives to-date in purse seine fisheries, with emphasis on FADs. ISSF Technical Report 2017-06. International Seafood Sustainability Foundation, Washington, D.C., USA.