Yellowfin tuna

Yellowfin tuna in the Eastern Pacific Ocean is not thought to be overfished or subject to overfishing.The Eastern Pacific Ocean (EPO) yellowfin tuna stock is managed and assessed by the Inter-American Tropical Tuna Commission (IATTC). Catches of yellowfin tuna in this area increased from 100,000t in the 1980s to over 400,000t in the early 2000s. They have since declined to around 233,000t (the average for 2015-2019).The most recent stock assessment for EPO yellowfin was carried out in 2020. As part of this, a number of stock status indicators were developed. The actual values for fishing pressure and biomass are not known, but it does assess stock status using MSY-based reference points. The next assessment is expected in 2024.The assessment concluded that at the beginning of 2020, the spawning biomass of yellowfin ranged from 49% to 219% of the level associated with Maximum Sustainable Yield (MSY). this is a wide range of values, but the probability of the spawning biomass being below MSY is low (12%), and there is a zero probability of it being below its limit reference point. Therefore, the stock is not thought to be in an overfished state.Between 2017 and 2019, the fishing mortality (F) for yellowfin ranged from 40% to 168% of the level associated with MSY. Again, this is a wide range of values but there is a low probability of F being above FMSY (9%) and zero probability of it being above the limit reference point. Therefore, the stock is not thought to be subject to overfishing.Recruitment of young fish into the stock appears to be declining, and has been below the long term average since 2000. There are occasional peaks, which may be influenced by El Nino events.Tagging studies of yellowfin throughout the Pacific indicate that they tend to stay within 1,800 km of their release positions. This tendency to stay within the same area, along with variation in characteristics of yellowfin between areas, suggests that there might be multiple stocks of yellowfin throughout the Pacific Ocean. However, movement between these potential stocks cannot be estimated with currently-available tagging data. This is the main uncertainty in the current stock assessment.

Few appropriate management measures are in place. There are controls relating to which fishing gears can be used where and when. However, there are no catch limits. Regulations are insufficient to prevent catches from increasing further and potentially exceeding sustainable limits.Tuna 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. It is important that commercial buyers choose tuna that has been caught by vessels that are well regulated by their flag state.This stock is managed and assessed by the Inter-American Tropical Tuna Commission (IATTC). Some stocks overlap with the Western and Central Pacific Fisheries Commission (WCPFC). The IATTC and WCPFC endeavour to work together to promote compatibility between their respective conservation and management measures across the Pacific, but this is not always achieved.Management of tropical tunas (bigeye, yellowfin, and skipjack) in the Eastern Pacific is through Resolutions that last for 3 years at a time. The conservation measures for tropical tunas in the Eastern Pacific Ocean during 2022-2024 (C-21-04) include a number of controls relating to which fishing gears can be used where and when. The aim is to keep fishing mortality at or below the status quo (average during 2017-2019). However, it does not include catch limits for yellowfin or skipjack. Therefore, not all appropriate management measures are in place.In 2016, interim Harvest Control Rules (HCRs) were brought in for bigeye, skipjack and yellowfin purse seine fisheries (C-16-02). The HCRs set out targets and limits for fishing mortality, which should be used as a basis for other management measures. Skipjack and yellowfin stock assessments are too uncertain to produce actual estimates of fishing mortality, although they have concluded that it is likely to be below the target reference point. However, some indicators show that fishing mortality is increasing on all three species owing to increases in purse seine fishing effort, specifically on Fish Aggregating Devices (FADs). Fishing mortality on skipjack in 2021 was above the status quo. This suggests that management may not be controlling fishing pressure, although the IATTC scientific committee have not recommended any changes to the current approach. There is a limit on the number of FADs each fishing vessel can use (varying by vessel size). FADs catch high numbers of juvenile yellowfin and bigeye, and are the main cause of increasing fishing pressure on tropical tunas. FAD limits are therefore seen as one of the most important ways to control tuna fishing. The upper limit for the largest vessels is gradually reducing from 450 in 2018-2021 to 340 by 2024, which is a 25% reduction. Recommendations were for a 30% reduction.A Management Strategy Evaluation for tropical tunas is being carried out from 2021-2024, beginning with bigeye tuna. This should provide some clarity on whether current measures can achieve their targets.Other management includes:Bigeye catch limits for longliners (varying by country). The scientific committee advises that if adequate management is in place for bigeye, this should also protect the skipjack stock.A ban on large purse seiners fishing in areas and at times when catches of small bigeye tuna are high. The closed periods are longer for vessels with higher bigeye catches.A requirement to retain and land all bigeye, skipjack, and yellowfin tuna caught by purse seiners.There is 100% observer coverage on large purse seiners to monitor catches and effort. The scientific committee continues to recommend 20% observer coverage for small purse seiners in order to get better data on discards and bycatch. Since 2011 only 5% observer coverage has been required on large longliners, considered by the scientific committee to be too low for accurate data: a minimum of 20% coverage is recommended. In addition, data recorded by longliners is considered inadequate for scientific purposes and minimum data standards must be identified and introduced.To help address IUU, the IATTC maintains an IUU Vessel List, maintains a register of authorised fishing vessels, prohibits transhipments at sea for most vessels (some exemptions apply), and requires most other transhipments to be documented and observed. Countries are required to report annually on monitoring, control and compliance of management measures. IATTC was the last tuna RFMO to adopt Port State measures (in 2021) to strengthen work to tackle IUU. IATTC does not report on countries' compliance with management measures and does not have a framework for addressing non-compliance.

A small amount of the yellowfin tuna catches in the Eastern Pacific Ocean are by longlining. Longlining in the SE Pacific is of particular concern as it is is one of the main causes of the decline in leatherback turtle in the area.Longline catches of yellowfin in the Eastern Pacific Ocean (EPO) have been steadily decreasing. It now accounts for around 4% of the total catch. While longlining is unlikely to have habitat impacts, it can have a bycatch of highly vulnerable and endangered species, including sharks, turtles, and seabirds.Data on bycatch in longline fisheries is very poor, partly because there are not enough scientific observers on vessels. Observer coverage is only required to be 5%, and recommendations are for at least 20%. The 5% target is often not achieved. Some mitigation measures are in place, but they often don't follow scientific recommendations for best practice, and their effectiveness has not been evaluated.The Eastern Pacific sub-population of leatherbacks is classified as Critically Endangered and at risk of extinction in the area. The population has declined by 90% since the 1980s. Bycatch and fishery interactions are the primary cause of the decline, mainly by gillnets and longlines in the southern and central Eastern Pacific (from Chile to Mexico). It is estimated that between 400 and 1,000 EPO leatherback turtles are killed by fishing each year, and the population was around 1,700 adults in 2015. An analysis by IATTC in 2022 indicated that the population was subject to overfishing by the fishery, and it was categorised as 'most vulnerable' to EPO fisheries. Urgent measures are needed to reduce impacts on this species, including better observer coverage, and improved handling and release practices to improve post-capture survival. This is in addition to current requirements, which include carrying equipment to promptly release turtles, record all interactions, and for shallow longliners to use circle hooks or finfish bait.Seabird bycatch is also a concern. Albatrosses and petrels are attracted to the baited hooks on longlines. There were at least 126 seabird deaths from EPO longlining in 2020, which is a minimum estimate given the significant data gaps. In previous years, interactions have been recorded with the waved albatross, which it is endemic to the EPO and nests only in the Galapagos Islands. The required mitigation measures do not follow recommended best practice by ACAP (the Agreement on the Conservation of Albatrosses and Petrels). IATTC requires one or more measures from a set list of options, including weighted branch lines, bird scaring lines and night setting. ACAP recommends the simultaneous use of all three, or hook-shielding or underwater bait setting devices.Sharks are both bycaught and targeted in longline fisheries in the EPO. An analysis published in 2022 indicated that 20 shark species in the eastern Pacific have high fishing mortality rates, including hammerheads, requiem sharks, threshers, whale shark, shortfin mako, and blue shark. A number of these are listed as vulnerable or endangered on the IUCN Red List. Longliners and large purse seiners using FADs and dolphins contributed the most to fishing mortality of these species.In 2020, over 14,000 tonnes of sharks were caught by longlining. The most commonly caught species are silky shark and blue shark. There are also some catches of the critically endangered oceanic whitetip and scalloped hammerhead, and the endangered pelagic thresher and mako species. Management measures include a ban on landing oceanic whitetips, silky sharks, and mobula rays, and restrictions on shark finning. The scientific committee continues to advise that shark data collection is inadequate and must be improved, and better mitigation measures are needed.Bycatch of marine mammals by longlining is not thought to be of concern in this fishery. There were 17 reported interactions in 2020, which is a minimum estimate, given the data gaps. Better data is needed to understand impacts.

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