Last updated on 5 July 2017
Improvement Recommendations to Catchers & Regulators
1. Provide data on discards and on the environmental impact of trawls.
2. Support biological data collection by all countries.
Recommendations to Retailers & Supply Chain
1. Contact your supplier and request that vessels provide data on discards and on the environmental impact of trawls.
2. Contact your national fisheries research institute and request that they collect biological data on this stock.
Stock assessment uses data from a triennial egg survey with catch-at-age data (ICES, 2009a). Different age-structured models are applied to the recent and historic periods and linked through a Separable-ADAPT VPA (SAD) model (ICES, 2009b). Not all countries with significant catches conduct biological sampling programmes. Although discard information is incomplete, discards and bycatch data from the main fleets are now included in the assessments; however discards for 2012 and 2013 were not included in the most recent assessment (ICES, 2014a). A fixed natural mortality of 0.15.year-1 is assumed for all ages and years (ICES, 2013a, 2013b).
There is uncertainty in the absolute estimates of Spawning Stock Biomass (SSB). The only fishery independent information is the triennial egg survey. If the assumption that fecundity at size is constant from year to year, the assessment results may be biased (ICES, 2013a). The landings sampling fraction has increase for 2013 (ICES, 2014a).
In 2010, ICES started a transition to a Maximum Sustainable Yield (MSY) approach where scientific advice will provide catch options according to the ICES MSY approach, the precautionary approach, and the management plan (ICES 2010c).
The western stock is considered a management unit and advised accordingly. The TAC is now set in accordance with the distribution of the stock although catches in IIIa are taken outside the TAC (ICES 2014b).
Western horse mackerel has been lightly exploited over its assessed history (average 1982–2013: F = 0.12). An interpretation of the Stock/Recruitment data shows high recruitment events at low Spawning Stock Biomass and no clear Stock/Recruitment relationship. Bloss is used as Bpa consistent with SGPRP (Further Development of the Precautionary Approach to Fisheries Management Study Group) logic on reference points (ICES, 2003b; ICES, 2014). There is a need to provide some biomass protection under the ICES MSY approach, and continued use of FMSY at low biomass may not be precautionary. Therefore, ICES uses Bpa as MSY Btrigger. In the present case this implies MSY Btrigger = Bloss.
As the management plan needs to be reviewed, the MSY approach has been used as basis for ICES advice. ICES’ MSY framework requires fishing mortality to be reduced to 0.12 in 2015, resulting in catches of less than 99,304 tons in 2015 (ICES, 2014a).
Fishing mortality at Maximum Sustainable Yield (FMSY) is defined as 0.13, and based on F0.1 from the Yield Per Recruit (YPR) analysis. Previously defined biomass reference points were considered not consistent with the state of the stock, exploitation rates and the evaluation of MSY reference points (ICES, 2010a). The target Fishing mortality (F) following the ICES MSY approach was determined as F=0.12 for 2015 (ICES, 2014).
The current status of the stock in regards to reference points is unknown, as there are no biomass reference points currently defined. Spawning stock biomass (SSB) is on a declining trend and is estimated to be at historical low levels, well below the long-term average and the previously defined Blim (ICES, 2013a). SSB is estimated to be at 772,334 tons in 2013 and is expected to decline below MSY Btrigger in 2014. Fishing mortality has been increasing since 2006 and it’s currently well above FMSY (= 0.13). Recruitment levels remain low since 2004 (ICES, 2014a).
Landings rose quickly from low levels (<100,000 tonnes) in the early 1980s to peak at 540,000 tonnes in the mid-90s but then declined back almost to late-80s levels. Since 2008, landings have been oscillating around 150-200 thousand tonnes. Fishing mortality decreased until 2006 from a peak in the late 90s, but has been increasing in recent years and is above FMSY since 2010. Since 2005, the fishery has been more directed toward younger fish (ages 1–3) than fish of ages 4 to 8. In 2012, fishing mortality on younger ages reached a record-high level (F=0.207). Recruitment is generally relatively low when compared to the extraordinarily strong year-classes which very occasionally occur. Spawning stock biomass has been decreasing since 2008 and is currently at historical low levels, well below the long-term average (ICES, 2013a).
A management plan was proposed by the Pelagic Regional Advisory Council in July 2007 with the aims of providing for the long-term sustainability of yields and for stability in TACs (ICES, 2010a). In its latest evaluation of the plan, in 2013, ICES concluded that “in its current configuration, the HCR is not consistent with the PA”. ICES stated however that through the introduction of a biomass trigger in the HCR, the management plan could be made consistent with the precautionary approach (PA) (ICES, 2013a).
In 2010, management areas for North Sea and Western Horse mackerel were rectified, so they would better reflect the distribution and fishing areas of the different horse mackerel stocks (ICES, 2010a). As a consequence, set TACs for Western horse mackerel are now divided in two parts: 1) Division VIIIc (13,572 tons); 2) EU waters of IIa, IVa, VI, VIIa-c, VIIe-k, VIIIa-e, EU and international waters of Vb, XII and XIV (85,732 tons), resulting a total TAC for 2015 set at 99.3 million tons, (EU 2014), in line with ICES advice (ICES, 2014a). However, the set TAC for 2015 was reduced in 26% in comparison with the previous year.
The minimum landing size of horse mackerel by the EU fleet is 15cm (10% undersized allowed in the catches). In Norwegian waters there is no quota for horse mackerel, but existing regulations on bycatch proportions as well as a general discard prohibition (for all species) apply (ICES, 2012b).
Historically, compliance by fishers with the set TACs was poor until the late-90s. Since 2000, compliance has oscillated, but for the majority of years catches still remained above TACs. The mismatch between management areas and ICES advice has also resulted in an overshoot of the advised catch levels prior to 2007 (ICES, 2013b). However since 2012 catches were below the agreed TAC (2012= 6%, catches 173,000 tons / agreed TAC 183,000 tons; 2013 =10%, catches 165,269 tons/ agreed TAC 183,000 tones) reflecting a best fishers compliance (ICES, 2013a; ICES, 2014).
Not all countries provide data on discards, but discards are considered negligible (at 3%) (ICES, 2014). Misreporting of juvenile catches is still an issue in some areas (ICES, 2013b).
The extent of the stock’s distribution region from northern Iberia northwards through the Celtic Sea and into the Norwegian Sea implies an overlap with many of the most populated seabird breeding and migrating grounds on European coasts. Rare species of elasmobranchs including large shark species are considered vulnerable in the Celtic Sea due to overfishing (ICES, 2008c).
In the past, cetacean bycatch has been reported has an issue for horse mackerel trawlers in the Celtic Seas, mainly for small cetaceans – white-sided, common, bottlenose and white-beaked dolphins, porpoises and smaller whales such as long-finned pilot whales and minke whales (Couperus, 1997; ICES, 2008c; Morizur et al., 1999). None of these are known to be endangered in the region (IUCN, 2013). To the north, fisheries bycatch of harbour porpoise and seals has been reported in the past (ICES, 2008c), but not recently (ICES, 2013c). Since 2005, the bycatch of five pilot whales was recorded in the midwater trawl fisheries in ICES area VIfghj (ICES, 2013c). Currently, however, cetacean bycatch is assumed to be very rare in the pelagic trawling for the small pelagic fish (ICES, 2013c).
Marine mammal interactions with purse-seine fisheries was recorded but compared with other fisheries, purse-seine fishing does not seem to be among the most damaging to marine mammals (Wise, et al., 2007; López et al, 2003). Purse-seines bycatch mainly occurred in shallower waters (<100 m) and according to fishers, animals encircled in purse-seines usually survived, either by escaping unaided or being helped to escape by the lowering of the corkline. (Goetz et al., 2013)
In terms of indirect effects of the fishery in PET species, Horse mackerel is part of the diet of several top predators in the southern region including cetaceans and seabirds (ICES, 2009b), but indirect effects of the fishery are not fully known. Fisheries may have a considerable influence on seabird populations through a supply of discards (e.g. Garthe et al., 1996; Granadeiro et al., 2013), but the lack of information on discarding in this fishery means effects are hard to estimate.
Bycatch reported by the Dutch fishery, the largest for horse mackerel, includes mackerel (Scomber scombrus) and, to a lesser extent, sardine (Sardina pilchardus) and blue whiting (Micromesistius poutassou) (Couperus, undated). Purse-seines have a low bycatch of non-target species (ICES, 2013). However, both bycatch and discards information is incomplete for this stock (ICES, 2011a).
Purse-seines have a low bycatch of non-target species (ICES, 2013). However, bycatch and discards information is incomplete for this stock (ICES, 2011a; ICES, 2014).
Horse mackerel is taken in a variety of fisheries, generally for the human consumption market, with the smallest sizes (juveniles) destined for the Japanese market and adult fish destined mostly for African markets (ICES, 2013a). Migrations are closely associated with the slope current, and horse mackerel migrations are known to be modulated by temperature (ICES, 2013b). Horse mackerel is a pelagic species but its behaviour is closer to a demersal species (ICES, 2009b). Although catches are mainly from pelagic trawl, it can also be taken by purse seine and bottom trawl, in either targeted or mixed fisheries. Bottom trawling is known to impact on benthic communities, and this has been observed in the Bay of Biscay, with a decrease in the mean trophic level of demersal and benthic fisheries and severe declines in some fish and crustacean species (ICES, 2008c).
The cold-water coral Lophelia pertusa is a recent subject of concern due to the diverse community found associated with it and the damage that is found to be caused by trawling (ICES, 2002). It is abundant in areas of the Bay of Biscay (ICES, 2002), the Celtic Sea (ICES, 2008d) and the Norwegian shelf, and several area closures to bottom trawling are in place to protect it (ICES, 2008c).
There are no areas specifically closed to this fishery (PRAC, 2007b) but it may be affected by closures to purse seining or bottom trawling that may be enforced seasonally or spatially by individual countries.
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. ICES’ reply to a request to evaluate possible fishery management measures for a proposed Natura 2000 site off Spain’s northern coast included a suggested extension of the area to cover the potential reef habitat and the exclusion of bottom trawling (ICES, 2008e).
Purse-seines are considered to have a little impact on the seabed since purse seiners operate in open waters (ICES, 2013).