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 interbenchmark 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 (ICES 2018), including the tagging data. 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).

ICES advises that catches in 2019 should not exceed 770,348 metric tons, under an approach aimed at fishing in the long term at maximum sustainable yield (MSY). This advice, issued in May 2019 (ICES 2019), replaces the September 2018 advised 318,403 metric tons, which had represented a significant reduction to 2018's advised 550,948 metric tons, due to the 2018 assessment's finding of both a declining stock and a downwards revision of the previous assessed stock size, along with high fishing mortality and low recruitment (ICES 2018). Concerns over the influence of tagging data on the 2018 assessment results led to the development of an interbenchmark 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).

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).

Re-estimated 2019 assessment results indicate that the stock is above its MSY B_trigger point and precautionary and limit reference points (ICES 2019). The previous 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. Fishers had reported increases in mackerel numbers in recent years (ICES 2018), a contradiction with assessment results which had also occurred in past seasons. 

Fishing mortality is 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. 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 the information on abundance of younger fish, which has led to an upwards 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) but in 2019 the plan was not followed by its signatory countries, who set a TAC constrained by a maximum 20% reduction, even though the stock was at that point determined to be below its MSY trigger point, so the TAC constraint would not have applied under the plan. 

Summed quotas set by all fishing parties have continuously exceeded advised catch levels (ICES 2018). 

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 2018).

With the exception of 1994 and since 2009, 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.

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. Limited information is available on bycatch of marine mammals by the fishery but it has been documented in mackerel trawling off southwest Ireland (ICES, 2008c), although, apart from long-finned pilot whale whose status is unknown, it mostly affects non-endangered mammals (IUCN, 2009). Mackerel is an important food source for various marine mammals (ICES, 2008a), but no information could be obtained on the indirect effects of removal of a preferred prey species.

Nesting or overwintering seabirds may also be affected by the fishery on several levels: bycatch of seabirds may occur, though most often documented for longline fishing, and discarding in the fishery can have a considerable impact on the distribution of scavenging seabirds (ICES, 2008c) 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.

Overall, the bycatch of non-target species in the mackerel fishery is considered minimal (ICES, 2011a). 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 distribution of mackerel spawning areas has changed in recent years and mackerel is being fished in areas where it was not previously found (ICES, 2009b). A westerly shift in the distribution of the mackerel stock is suggested by survey data in 2009 (ICES, 2009b). Consequences of this change can be expected to be substantial and to impact on the future abundance, spawning, growth and recruitment of the stock (ICES, 2008a). High ocean temperatures appear to be influencing mackerel distribution and migration patterns, partly due to high zooplankton concentrations in the western Norwegian Sea (ICES, 2009b). Earlier spawning in the south and earlier migration to northern waters also appear to be a result of the warmer seas and are supported by changes in the timing of the southern fisheries (ICES, 2008a). An increase in the variability of recruitment has also become apparent in recent years (ICES, 2008b).

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

Last updated on 08 Nov 2012

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, the extension to marine areas of the EU Natura 2000 network of special conservation areas, under the Birds Directive 79/409/EEC and the Habitats Directive 92/43/EEC is currently underway and special fishery management measures may be applied.