Atlantic mackerel

An age-based analytical model (SAM) is used in the assessment, based on catch and tagging data and three survey indices. Partial discarding estimates are included in the assessment but recent discarding is not thought to be significant (ICES 2018).

An inter-benchmark process reviewed and modified the assessment in 2019, reducing the influence of the tagging data on the assessment, which significantly revised the 2018 assessment results, highlighting the instability of the assessment (ICES 2019).

Some conflicting signals are apparent in the data sources used and some of the time series are still short. Since the updated assessment, a substantial retrospective bias for fishing mortality (F) was verified (F was overestimated by more than 20%) (ICES 2019). Additionally, the distribution of the stock is very broad and has shifted over time and surveys may not be fully sampling the stock (ICES 2019).

The ICES recommends that onboard observer programs should be reinforced since discards can have great implications in the assessment of this species (ICES 2019).

Concerns over the influence of tagging data on the 2018 assessment results led to the development of an inter-benchmark process in 2019 to revisit the assessment method. A new method was proposed (ICES 2019) which was used to revise the 2018 advice in May 2019, leading to an upwards revision of the stock size, to above MSY B_trigger, and a downwards revision of fishing mortality, as well as an upwards re-estimate of the value of F_MSY (ICES 2019).

For 2020, ICES advises that catches should not exceed 922,064 metric tons, under an approach aimed at fishing in the long term at maximum sustainable yield (MSY). This advice, issued in october 2019, increased the TAC advice in 20%  in relation to the updated advice for 2019 (published in May 2019) considering that the highest year-classes (2016 and 2017) are entering in the fishery and started to contribute to the reproductive stock (ICES 2019).

One of the three spawning components, that in the North Sea, is still of a reduced size due to earlier overexploitation, and ICES continues to recommend protection measures including closed areas and seasons and a minimum size (ICES 2019). ICES also advised that a minimum conservation size of this component of the stock needs to be established (ICES 2019).

The last assessment (October 2019) results indicate that the stock is well above its MSY B_trigger point and precautionary and limit reference points (ICES 2019). The 2018 assessment had indicated that the stock had decreased to below its MSY B_trigger point in 2018, for the first time since 2007, but this was revised (May 2019). Fishers had reported increases in mackerel numbers in recent years (ICES 2018).

Fishing mortality is slight above F_MSY, and has been above this newly calculated reference point since 1985. It is below its precautionary and limit reference points however. Catches have been increasing since the mid-2000s, and are considered to be considerably underreported prior to 2000. Catches estimates decreased about 11% between 2017 and 2018 (ICES 2019). Recruitment was strong from the early 2000s but the 2015 and 2016 classes had appeared to be small in the 2018 assessment, contributing to the reduction in stock size (ICES 2018). The 2019 review changed the model with regards to the information on abundance of younger fish, which has led to an upward revision of estimated recent recruitment. Recent recruiting classes are now thought to be strong (ICES 2019).

TACs were previously agreed amongst all fishing parties, but since 2008 no agreement has been reached on setting TACs, and quotas have been set unilaterally. In 2014 three of the Coastal States (Norway, the EU and the Faroe Islands) reached an agreement, that was later extended to 2020, including a harvest control rule that uses MSY reference points and linearly reduces the TAC when the stock is below its MSY trigger reference point (Anon 2018). ICES found the strategy to be precautionary in the long term (ICES 2017). However, there is no a long-term management strategy agreed by all states participating in the fishery. 

Management measures include a minimum landing size (MLS) for mackerel set at 30 cm for the North Sea and 20 cm in the western area. Other additional measures are in place to protect the North Sea component (e.g. closed areas) (ICES 2019).

Summed quotas set by all fishing parties have continuously exceeded advised catch levels although the sum of the unilateral TAC has been decreasing in the last 2 years (ICES 2019)​.

Total mackerel catches are estimated by ICES and include discards where available, but are considered to be underestimated due to discards, slippage and under-reporting, although discarding and slipping is thought to have decreased (ICES 2019). This stock is target mainly by a directed fishery for human consumption by Norway (18%), Iceland (16%), Scotland (15%), Russia (12%) and Faroe (8%) (Hough et al. 2016)(ICES 2019).

In general, total catches have surpassed set TACs. From 2009, catches have been close to the sum of the quotas set for the entire area, but considerably exceeded ICES’ advice, and have been increasing since 2006. Fishing mortality was also above that foreseen in the management plan, when this was in force. According to ICES, the lack of international agreements on the exploitation of the stock since 2008 is of critical concern, and hinders control of the total exploitation rates.

The Marine Stewardship Council (MSC) suspended all MSC certificates associated to this fishery in March 2019 due to the lack of a long-term strategy agreed by all countries involved in this fishery and due to the recurrent catches volumes above the advised values.

The stock is distributed through a vast area, and many marine mammals, seabirds and other endangered, threatened or protected (ETP) species are known to occur in these waters. A wide variety of marine mammals, including several species of whales considered by the IUCN to be endangered, and hooded seals, classified as vulnerable (IUCN, 2009), overlap with mackerel’s distribution in the North-east Atlantic. Data on bycatch of protected species have been collected by observers and there is no evidence that ETP species have been affected by the pelagic trawl fisheries in NE Atlantic although this gear has been classified as bycatch medium risk (Hough et al. 2016)(ICES 2019). Also, the bycatch of small cetaceans by pelagic trawl is considered low (ICES 2017).

Nesting or overwintering seabirds may also be affected by the fishery on several levels: bycatch of seabirds may occur (ICES 2018) but no specific information is available on the effects of the mackerel fishery on seabirds in the region.

Many elasmobranchs in the region which also increasingly vulnerable and marine turtles reported towards the south of mackerel’s range (ICES, 2008c) could be at risk of bycatch but no reports are available.

NE Atlantic mackerel is mainly targeted by pelagic trawl (83%) and purse seine (17%) (ICES 2019). Overall, the bycatch of non-target species in the mackerel fishery is considered minimal and gear improvements has been increasing selectivity (Hough et al. 2016) (ICES 2019). There is some overlap with the Norwegian Spring-Spawning (NSS), in the northern extent of the Atlantic mackerel range, creating some bycatch issues for the vessels targeting mackerel in this area (ICES, 2009b; ICES, 2011b). The other non-target species in this fishery are herring and horse mackerel but together represent less than 1% of the total catch (Hough et al. 2016).

From 2019 onwards the EU landings obligation is generally effective which bycatch and discards are expected to remain at low levels. There are specific exemptions (de minimis) for mackerel caught in bottom-trawl fisheries in the North-Western Waters and in the North Sea. A general discard ban is already in place for Norwegian, Faroese and Icelandic fisheries (ICES 2019).

Slipping (i.e. the release of unwanted catch still in the water) is not allowed in Faroese waters (Kiseleva et al. 2016). The slipping of small pelagic species like mackerel can lead to high rates of mortality (Marçalo et al. 2019).

Most fleets target mackerel with pelagic gear (midwater trawl), where direct effects on the habitat and seabed are not thought to be significant (Kiseleva et al. 2016), but demersal trawls are used by Spanish fleets and are known to damage benthic communities besides having a larger rate of discarding (ICES, 2008c).

Several areas in NE Atlantic waters where defined to protect vulnerable marine environments (VME) such as coldwater corals and sponges (ICES 2019). See VME map here.  

The south-west mackerel box, an area off the coast of Cornwall in Southern England, was set up in 1981 in order to protect juvenile mackerel in a known nursery area, at a time when fishing effort was particularly high and discarding of small mackerel a major issue. The area was further expanded in 1989 and is closed to mackerel fishing with the exception of handliners. The fishery is also closed in Divisions IIIa and IVb,c on a permanent basis in order to protect the North Sea component and Western juveniles and in Division IVa during the first half of the year (ICES, 2012a).

In addition, in EU waters there are marine areas of the EU Natura 2000 network of special conservation, under the Birds Directive 79/409/EEC and the Habitats Directive 92/43/EEC in place. 

Northeast Atlantic mackerel is a widely distributed species from Iberian waters to North Norway, Iceland, and Greenland. The spatial distribution of mackerel changed in the last decade influenced by several environmental factors, as the water temperature (Nikolioudakis et al. 2019), starting to be fishing in northern areas (Jansen et al. 2016). This also implied changes in the fishing season for mackerel, for example, occurring early in the Cantabrian Sea reflecting changes in mackerel behavior migration in response to climate change effects (ICES 2018).

This species is crucial for the ecosystem, as predator and prey: mackerel feeds on zooplankton and larval and juvenile stages of small fish and mollusks and is prey by other fish species, seabirds, and marine mammals. Mackerel, herring and blue whiting might be strong competitors in certain areas (Trenkel et al. 2014). There are other important species interactions: cannibalism and interspecific predation (e.g. herring) (ICES 2019).

ICES Working Group (WGWIDE) recommends more studies on the ecosystem implications of this widely distributed species, including the NE Atlantic mackerel, Norwegian spring-spawning herring, blue whiting and horse mackerel (ICES 2019).