Yellowfin tuna

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.Yellowfin tuna in the Atlantic is 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 190,000 tonnes in 1990 to 100,000t in 2007, and subsequently rose to an average of 140,000 tonnes from 2016-2020. Biomass has continuously declined throughout the lifetime of the fishery, while fishing mortality has been increasing since the mid-2000s.In 2018, biomass (B) was 117% of levels associated with Maximum Sustainable Yield (MSY). Therefore, the stock is not in an overfished state.Fishing mortality (F) in 2018 was just below the level associated with MSY, at 96%. Therefore, the stock is not subject to overfishing. However, the most recent catch estimates suggest that overall catches have exceeded MSY (120,000t) every year since 2015.The preliminary catch in 2020 was 148,894 tonnes. This is of concern to the scientific committee because it exceeds the catch limit (110,000t) and is the highest since 2016. Projections indicate that catches above 120,000t would cause biomass to decline. At 140,000 tonnes, there is only a 20% probability that the stock will be above BMSY and below FMSY by 2030.Some catches are on Fish Aggregating Devices (FADs), which tend to catch smaller tunas, including juveniles. 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.

Few appropriate management measures are in place. Management is not effective at controlling fishing pressure on this stock. Catch limits have been exceeded in every year since 2015, at levels that are expected to cause the stock to decline.Tuna, marlin, and swordfish are highly migratory species, found on the high seas and in numerous countries' waters. This makes harmonised and effective management challenging. Regional Fisheries Management Organisations (RFMOs) are responsible for monitoring and managing these stocks on behalf of the countries that access them. However, the degree to which management is implemented, monitored and enforced by each country varies significantly.Atlantic yellowfin tuna is managed and assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). The main management measures are a catch limit (Total Allowable Catch, TAC) and controls on fishing gear.The TAC for yellowfin has been 110,000 tonnes since 2012. Scientific advice is that keeping catches at 120,000t or less is expected to maintain healthy stock status through to 2033. This indicates that catch limits are following scientific advice.However, catches have exceeded the TAC every year since 2015. Average catch from 2016-2020 is 140,000 tonnes, which is expected to cause the stock to decline. The scientific committee has suggested that existing conservation and management measures appear to be insufficient and need to be strengthened.Most yellowfin tuna catches are by purse seine nets, many of which use Fish Aggregating Devices (FADs). FADs are floating objects that attract tuna and other species, making it easier to set nets around them to catch them. Many juvenile fish are caught in these fisheries, which can have implications for future population growth. 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.Consequently, a multi-annual management plan has been in place for bigeye and yellowfin since 2012, and eastern skipjack since 2015. It is mostly focussed on FAD management. Initially there was a 2-month FAD ban in an area where there are high concentrations of juveniles, and a 500 FAD limit per vessel for the rest of the year. This failed to reduce the mortality of juvenile bigeye and yellowfin tuna, so additional measures were added in 2019. The number of FADs per vessel was reduced to 300 for 2021 and 2022. The FAD ban was extended to the full convention area, lasting for 72 days in 2022 (January to mid-March). In 2021 the scientific committee advised that it was too soon to evaluate the impact of these changes. In 2021 the number of permitted support vessels, which help to increase the efficiency of purse seiners, was frozen.As well as the above measures, there is a ban on discarding skipjack, yellowfin and bigeye tuna, so that all fish caught must now be landed. There is also a tagging programme to improve stock assessments for tropical tunas and gauge effectiveness of management measures. This helped to improve the quality of the 2019 yellowfin assessment.Other management by ICCAT includes:A ban on drift nets by the EU in 2002 and by ICCAT in the Mediterranean in 2003.A list of vessels authorised to fish for this species, 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.A requirement for 100% observer coverage on large purse seiners targeting tropical tunas all year round. The requirement for longline is only 5%, increasing to 10% in 2022. Many fleets are not reaching this level. Scientific recommendations are 20% for accurate data. Work is underway to improve electronic monitoring. Vessel Monitoring Systems are required for all vessels over 24m.

Most yellowfin tuna from the Atlantic is caught by purse seining. This method is associated with bycatch of species such as sharks, turtles and marine mammals.Purse seining accounts for 68% of Atlantic yellowfin tuna catches (around 107,000t in 2020). Approximately one third of purse seine catches are from Fish Aggregating Devices (FADs) and the rest is on free schooling tuna, but it is not always possible to verify which catches are from which method.Purse seining is associated with bycatch of species such as sharks, turtles and marine mammals, although less so than longlining. Bycatch is higher when FADs are used. FADs are floating objects that tuna and other species tend to aggregate around. It is estimated that 7% of the total catch (by weight) in FAD fisheries in the Atlantic is non-target species, as opposed to 1.8% in free-schooling fisheries.FADs can include hanging elements such as ropes and nets, which can entangle vulnerable species. FADs can also become lost at sea, continuing to ghost fish and be a source of marine debris. Some mitigation measures are in place. Countries must use non-entangling FADs and phase out non-biodegradable FADs. They must also have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem. All large purse seine vessels fishing for tropical tunas must have an observer, which can improve understanding of bycatch and help to improve compliance with management measures.The main bycatch concern is sharks, which are severely threatened by fishing activity. Sharks are both bycaught and targeted in fisheries in the Atlantic. Bycatch species include the critically endangered scalloped hammerhead, silky shark, and the bigeye thresher, which is endangered in Europe and the Mediterranean. Observer data for 2020 indicates 1,098 dead discards of sharks and 1,109 live discards. Given the poor observer coverage in longline fisheries, which is only 10%, this is likely to be an underestimate of the total catch. There are some mitigation measures, such as a ban on finning, but no gear-specific measures. 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. However, measures are came into force in 2022 to end overfishing of this species. 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.There is also a bycatch of loggerhead, leatherback and olive ridley turtles in longline and purse seine fisheries. According to the IUCN Red List, loggerhead turtles are endangered in the north east Atlantic and leatherbacks are endangered in the north west Atlantic and critically endangered in the southwest Atlantic. Observer data for 2020 indicates 20 dead discards of turtles, 1,308 live discards and 20 discards of unknown status. As above, with the poor observer coverage, this is likely to be an underestimate. Post-release mortality is 1-4%. Longliners are required to safely unhook and release alive turtles, and purse seiners must avoid encircling them. Other scientifically recommended mitigation measures, such as using finfish bait and large circle hooks, are not mandated.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.The fishery is not considered to be a threat to seabirds.FADs are also of concern due to the unknown impacts such gear might have on other tuna and fish species in relation to species composition of schools, migratory patterns, growth rates and predation rates. Juvenile and bigeye tuna are caught by purse seining, and scientific recommendations are for these impacts to be reduced to protect the stocks.

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