Skipjack tuna

East Atlantic skipjack tuna is abundant and is not subject to overfishing.Skipjack stocks in the Atlantic are assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). A new stock assessment was carried out in 2022, the first since 2014. It uses data up to 2020.East Atlantic catches have steadily increased since 1960, reaching a record 284,000t in 2018 and falling to 197,000t by 2021.The biomass (B) of the stock has gradually declined since the 1950s, but has stayed above the level associated with Maximum Sustainable Yield (B MSY). In 2020, B was 160% of BMSY. There is some uncertainty in this: the range of estimates for biomass are 50%-579% of BMSY. However, the assessment indicates that the stock is not in an overfished state with 83% probability.Fishing mortality (F) has steadily increased since the 1960s, but has stayed below F MSY. In 2020, F was 63% of FMSY. Therefore, the stock is not subject to overfishing.Projections are uncertain because of the wide range of biomass estimates. However, they indicate that a constant catch at MSY (216,617t) would result in a 17% probability of the stock being below Blim (20% of BMSY) in 2028.This is a significant improvement in the understanding of the stock, as there had not been assessment since 2014. The 2014 assessment gave no estimate of MSY, but there were concerns that catches could be above it. Scientific recommendations were for no more than 218,000 tonnes, and catches in 2016-2020 averaged 244,000t.

Few appropriate management measures are in place for this stock. Recent catches have exceeded recommendations and there are no catch limits.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.East Atlantic skipjack tuna is managed and assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). In spite of scientific recommendations and attempts to develop a Harvest Control Rule (HCR) for eastern skipjack, there is no TAC (Total Allowable Catch) or HCR in place for this stock. The primary management measure is a limit on Fish Aggregating Devices (FADs).A new stock assessment for Atlantic skipjack was carried out in 2022. This was a significant improvement in the understanding of the stock, as there had not been an assessment since 2014. The 2014 assessment gave no estimate of MSY, but there were concerns that catches could be above it. Scientific recommendations were for no more than 218,000 tonnes, and catches in 2016-2020 averaged 244,000t. Until recently, therefore, management had not been following available scientific advice, and was unable to accurately manage the stock without up to date stock information.The new assessment indicates that the stock is in a healthy state and that a constant catch at MSY (216,617t) would result in a 17% probability of the stock being below Blim (20% of BMSY) in 2028. Recent catches (2017-2021) have been above MSY, averaging 240,500 tonnes, although they have been declining and in 2021 were 196,987t.Fishing for skipjack also affects other species that are caught with it, particularly juvenile yellowfin and bigeye tuna in the purse seine FAD fisheries. Therefore, fishing at MSY for skipjack may have a negative impact on these species, and catches may need to be reduced further.Most eastern skipjack 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. Therefore, there is a ban on using FADs throughout the Atlantic (ICCAT convention area) for 72 days in January to mid-March. This is intended to reduce fishing pressure on bigeye and yellowfin tuna. In 2022, the scientific committee concluded that it also may have reduced skipjack catches.The number of FADs that each fishing boat can use has been reduced from 500 in 2018 to 300 from 2021-2023. It is unclear what effect this has had on the stock.The current management is not guaranteed to control skipjack catches. Recent catches have been above the recommended level, and there remain no harvest control rule or catch limits to ensure that they stay at sustainable levels. Therefore, few appropriate management measures are in place for this stock. Further measures are expected to be considered and developed in 2023.Management measures also include:Countries must calculate the fishing capacity needed to deliver their set quotas, and reduce current capacity, e.g. by reducing licenses or vessel sizes, if it is too high. An analysis in 2022 estimated that in total there are 72 purse seine vessels actively fishing in the area, with a higher capacity (fish-hold volume) than needed. There were 99 vessels licensed to fish in the area, so there is also excess latent capacity.Countries are 'encouraged' not increase fishing effort above the 2018 level.Countries must submit FAD management plans to improve knowledge about FADs being used, manage deployment and recovery, and reduce ecosystem impacts.In 2021 the number of permitted support vessels, which help to increase the efficiency of purse seiners, was frozen.A requirement for 100% observer coverage on large purse seiners targeting tropical tunas all year round. The requirement for longline is only 10% and many fleets are not reaching this level. Scientific recommendations are 20% for accurate data.There is a ban on discarding skipjack, yellowfin and bigeye tuna: all fish caught must be landed. There is also a tagging programme to improve stock assessments for tropical tunas and gauge effectiveness of management measures.In terms of monitoring and surveillance, 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.Work is underway to improve electronic monitoring. Vessel Monitoring Systems are required for all vessels over 24m.

Most skipjack tuna from the east 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 around 80% of east Atlantic skipjack tuna catches (around 165,500 tonnes in 2021). Most purse seine catches (90%) are from Fish Aggregating Devices (FADs) and the rest is on free schooling tuna. It is not always possible to separate FAD and FAD-free catches, so they are covered in the same rating.Monitoring and reporting of bycatch in fisheries managed by ICCAT is generally poor. Most data come from scientific observers on vessels. Recommendations are that 20% of a fishery should be observed for accurate data, but some ICCAT fleets have just 10%. While coverage on large purse seiners targeting tropical tunas is 100%, the data provided is for all gears combined so this does not do enough to improve understanding of bycatch. This makes it difficult to assess the impact of these fisheries on vulnerable species.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.From 2021, FADs used in Atlantic tuna fisheries must not not have elements that could entangle other species. However, there is a risk that FADs can become lost at sea, continuing to ghost fish and be a source of marine debris. Some mitigation measures are in place. Countries should phase out non-biodegradable FADs. They must also have FAD Management Plans that improve understanding of FADs and limit their impacts on the ecosystem.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 all gears for the whole Atlantic for October 2021 - October 2022 indicates: 804 dead discards of sharks and 1,082 live discards. Data on the impact of individual fisheries is not publicly available. Given the poor observer coverage, this is likely to be an underestimate of the total catch. There are some mitigation measures, such as restrictions 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 came into force in 2022 and 2023, aimed at ending overfishing of this species. Currently there is not enough data to properly assess the status of many pelagic sharks. No shark assessments have been carried out for the Mediterranean.There is a bycatch of loggerhead, leatherback and olive ridley turtles in longline and purse seine fisheries, especially when FADs are used. 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 all gears for the whole Atlantic for October 2021 - October 2022 indicates: 190 dead discards of turtles, 3,752 live discards and 69 discards of unknown status. Given the poor observer coverage, this is likely to be an underestimate of the total catch. Data on the impact of individual fisheries is not publicly available. Post-release mortality is 1-4%. Longliners are required to use circle hooks or finfish bait and safely unhook and release alive turtles, and purse seiners must avoid encircling them.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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