Draft Fisheries Assessment – West Shetland Shelf NCMPA: Fisheries management measures within Scottish Offshore Marine Protected Areas (MPAs)

3. Part B Assessment – Fisheries Assessment

3.1. Fisheries assessment overview

Part B of this assessment considers if there would be a risk of the fishing activities identified in part A, at the levels identified in the relevant date range, hindering the achievement of the conservation objectives for the MPA. This is in order to consider whether, and if so, which, management measures might be appropriate for the MPA, taking into account all relevant statutory obligations incumbent upon the Scottish Ministers.

The fishing activities identified in Part A which have been included for assessment in Part B are mobile demersal fishing (trawls, seines, and boat dredges) and static demersal fishing (traps/creels and anchored nets/lines). The pressures associated with these fishing activities that have been included in Part B are abrasion/disturbance of the substrate on the surface of the seabed; penetration and/or disturbance of the substrate below the surface of the seabed, including abrasion; changes in suspended solids (water clarity); smothering and siltation rate changes (light); and the removal of non-target species.

3.2. Fishing activity descriptions

3.2.1. Existing management within West Shetland Shelf NCMPA

The Technical Conservation Regulation 850/98 delineated an area closed to mobile fishing gears known as the 'Windsock' which overlapped the West Shetland Shelf NCMPA, offering some protection to the benthic features of this site. However, new Technical Conservation Regulations (Regulation (EU) 2019/1241) were introduced in 2019, lifting the Windsock restrictions as of 14 August 2019. Since lifting these restrictions, the fishing industry have put in place voluntary measures to manage mobile/static gear conflict. In 2020, the fishing industry agreed voluntary measures across the site which resulted in a split between static and mobile gears and a shared area, with the areas for each gear type being switched on a regular basis. These voluntary measures are to continue until the implementation of fisheries management measures (Section 5), at which point the rotation of access will then apply to the three zones open to mobile gear.

No other fisheries management measures or other fisheries restrictions were identified within the site.

3.2.2. Fishing activity within West Shetland Shelf NCMPA

The West Shetland Shelf NCMPA overlaps ICES rectangles 47E3, 47E4, 47E5, 48E3, 48E4, 48E5 and 48E6 in both the West of Scotland (ICES Division 6a) and Northern North Sea (ICES Division 4a), in the North Scotland Coast region. The aggregated gear methods used in West Shetland Shelf NCMPA by UK vessels are demersal trawls, demersal seines, traps/creels, and anchored nets/lines; boat dredges are used by foreign vessels (Table 1, in Section A). Pelagic fishing (mid-water trawls) was not considered capable of affecting the subtidal sands and gravels feature of West Shetland Shelf NCMPA as there is no contact with the seabed, and so this fishing activity is not considered further. Demersal trawls, demersal seines, boat dredges, traps/creels, and anchored nets/lines are considered in more detail in the following sections.

In addition to UK activity, vessels from Ireland (43 vessels), Faroes (38 vessels), France (24 vessels), Norway (13 vessels), Spain (10 vessels), Denmark (9 vessels), Netherlands (8 vessels), Germany (6 vessels), Sweden and Lithuania (number of vessels cannot be disclosed) may also operate in the site, based on VMS data from 2015-2019. However, it is not clear what gear types these vessels operate, nor whether they were actively fishing at the time.

3.2.3. Demersal trawls

The aggregated gear method of demersal trawls includes multiple gears that operated within the West Shetland Shelf NCMPA between 2015 and 2019. These include bottom otter trawls, multi-rig trawls, pair trawls, Nephrops trawls, and unspecified bottom trawls. Similar pressures are exerted by the different gears used for demersal trawling, subsequently the aggregated gear type of 'demersal trawl' was used to map activity across the site.

According to the VMS intensity averaged over 2015 to 2019, demersal trawling is concentrated in the central-southern part of the site (48 – 168, 24 – 48, and 12 – 24 fishing hours per year per grid cell), with small additional areas of increased intensity along the site boundaries (24 – 48 and 12 – 24 fishing hours per year per grid cell). The remainder of the site has lower fishing intensity (less than 12 fishing hours per year per grid cell) with demersal trawling activity absent from pockets in the eastern and western parts of the site (Figure 2).

Swept-Area Ratio (SAR) information averaged over the same time period shows similar patterns of fishing intensity as the VMS data (Figure 2). The highest SAR values are in the central-southern part of the site (cells swept 2 – 5 or 1 – 2 times per year per grid cell), with small additional areas of higher SAR values along the site boundaries (cells swept 2 – 5 or 1 – 2 times per year per grid cell). The rest of the site had low SAR values (cells swept less than once annually) with demersal trawling activity absent from pockets in the eastern and western parts of the site (Figure 2).

3.2.4. Demersal seines

The only demersal seine activity within the site between 2015 and 2019 was conducted using Scottish fly/seine gear. Fishing with this gear is referred to as the aggregated gear type of 'demersal seines' in the following sections to align with the approach taken for the rest of the assessment.

According to the VMS intensity averaged over 2015 to 2019, demersal seine activity is very low within the site. The only locations with demersal seine activity (less than 12 fishing hours per year per grid cell) are generally restricted to small areas in the eastern and central-southern parts of the site (Figure 3).

Swept-Area Ratio (SAR) information averaged over the same time period shows similar patterns of fishing intensity as the VMS data (Figure 3), with low levels of demersal seine activity (cells swept less than once annually) in the eastern and central-southern parts of the site.

3.2.5. Boat dredges

The only boat dredge activity within the site between 2015 and 2019 was conducted using foreign vessels, hence the specific boat dredge gear type operating within the West Shetland Shelf NCMPA is unknown. Fishing with this gear is referred to as the aggregated gear type of 'boat dredges' in the following sections to align with the approach taken for the rest of the assessment.

According to the VMS intensity averaged over 2015 to 2019, boat dredge activity is very low within the site. The only locations with boat dredge activity (less than 12 fishing hours per year per grid cell) are in the central-southern part of the site (Figure 4).

Swept-Area Ratio (SAR) information averaged over the same time period shows similar paters of fishing intensity as the VMS data (Figure 4), with low levels of boat dredge activity (cells swept less than once annually) in the central-southern part of the site.

3.2.6. Traps/creels

The only gear within the aggregated traps/creels gear type operating within West Shetland Shelf NCMPA between 2015 and 2019 was pots/creels. Fishing with this gear is referred to as the aggregated gear type of 'traps/creels' in the following sections to align with approach taken for the rest of the assessment.

According to VMS intensity averaged over 2015 to 2019, trap fishing is concentrated in the northwestern part of the site (24 – 48, and 12 – 24 fishing hours annually), with additional areas of higher intensity in the southeastern and southwestern areas (12 – 24 fishing hours per year per grid cell). The remainder of the site has lower fishing intensity (less than 12 fishing hours per year per grid cell) (Figure 5). Swept-Area Ratio information is not available for static fishing, such as traps/creels.

3.2.7. Anchored nets/lines

The aggregated gear method of anchored nets/lines includes multiple gears that operated within the West Shetland Shelf NCMPA between 2015 and 2019. These include set longlines and longlines (not specified). Fishing with these gears is referred to as the aggregated gear type of 'anchored nets/lines' in the following sections to align with the approach taken for the rest of the assessment.

According to the VMS intensity averaged over 2015 to 2019, anchored nets/lines activity is very low within the site. The only locations with anchored nets/lines activity (less than 12 fishing hours per year per grid cell) are two small areas in the northeastern and southwestern part of the site (Figure 6). Swept-Area Ratio information is not available for static fishing, such as anchored nets/lines.

3.2.8. Fishing activity summary

Fishing activities using demersal trawls, demersal seines, boat dredges, traps/creels, and anchored nets/lines all occur within the West Shetland Shelf NCMPA.

Demersal trawling activity occurs at higher intensity in the central-southern part of the site, high intensity along the site boundaries, and lower intensity elsewhere except for some areas in the eastern and western parts of the site where demersal trawling is absent. Demersal seine and boat dredge activities are very low within the site and are restricted to small areas in the eastern or central-southern parts of the site. Traps/creels are concentrated in the northwestern, southeastern, and southwestern parts of the site. Anchored nets/lines activity is also very low within the site and is restricted to the northeastern and southwestern part of the site.

Given that the offshore subtidal sands and gravels feature spans the entirety of the West Shetland Shelf NCMPA, there is overlap between the areas exposed to demersal trawls, demersal seines, boat dredges, traps/creels, and anchored nets/lines, and the subtidal sands and gravels feature.

3.3. Fishing activity effects overview

The following sections explore the pressures associated with fishing activity (demersal trawls, demersal seines, and traps/creels) within the West Shetland Shelf NCMPA that were considered capable of impacting the offshore subtidal sands and gravels feature. The pressures considered in the following sections are:

• Abrasion/disturbance of the substrate on the surface of the seabed;
• Penetration and/or disturbance of the substrate below the surface of the seabed, including abrasion;
• Changes in suspended solids (water clarity);
• Smothering and siltation rate changes (light); and
• Removal of non-target species.

All five pressures, as exerted by mobile demersal fishing (trawls, seines, and boat dredges), were considered capable of impacting the subtidal sands and gravels feature. For static demersal fishing (traps/creels and anchored nets/lines), only abrasion/disturbance of the substrate on the surface of the seabed and removal of non-target species were considered capable of affecting the offshore subtidal sands and gravels feature.

Given the similarity between 'abrasion/disturbance of the substrate on the surface of the seabed' and 'penetration and/or disturbance of the substrate below the surface of the seabed', these two pressures are considered together in the text below. 'Smothering and siltation rate changes (light)' and 'changes in suspended solids (water clarity)' are also considered together. All pressures considered capable of impacting the protected feature are discussed under the aggregated fishing gear types of 'mobile demersal gears' and 'static demersal gear'.

In the absence of a detailed JNCC Advice on Operations spreadsheet for this site, the detailed pressure information for this section is based on information from the Management Options Paper for West Shetland Shelf (2014), JNCC PAD and FeAST. The West Shetland Shelf NCMPA offshore subtidal sands and gravels protected feature encompasses a range of sub-components including the EUNIS Level 4 habitats circalittoral coarse sediments, circalittoral mixed sediments, and circalittoral sands (JNCC, 2014). Within FeAST, the equivalent features are continental shelf coarse sediments, continental shelf mixed sediments, and continental shelf sands. These three features were used to determine the sensitivity of the offshore subtidal sands and gravels feature to fishing activity.

3.3.1. Impacts of mobile demersal gear (trawls, seines and boat dredges) on Offshore subtidal sands and gravels

As detailed in the JNCC Marine Pressures-Activities Database (PAD) v1.5 2022, abrasion/disturbance of the substrate on the surface of the seabed and penetration and/or disturbance of the substrate below the surface of the seabed, including abrasion, occur where gear makes contact with the seafloor. The area affected is determined by the footprint of the gear and the amount of movement across the seabed. The different gear components will make variable contributions to the total physical disturbance of the seabed and its associated biota, and hence the pressure will vary according to factors such as gear type, design/modifications, size and weight, method of operation (including towing speed) and habitat characteristics (e.g. topography) (Lart, 2012; Polet & Depestele, 2010; Suuronen et al., 2012). Towed bottom fishing gears are used to catch species that live in, on or in association with the seabed and therefore are designed to remain in close contact with the seabed. That interaction with the seabed can lead to disturbance of the upper layers of the seabed, direct removal, damage, displacement or death of the benthic flora and fauna; short-term attraction of scavengers; and the alteration of habitat structure (Kaiser et al., 2003; Gubbay & Knapman, 1999; Sewell & Hiscock, 2005; Collie et al., 2000; Kaiser et al., 2002).

Benthic seines are generally of lighter construction as there are no trawl doors or warps, resulting in less disturbance of the seabed than trawling (Polet & Depestele, 2010; Donaldson et al., 2010; Suuronen et al., 2012). As a relative comparison of gear types, otter trawls tend to have less physical impact on the seafloor than beam trawls (and dredges) with the heavy thicker chains of beam trawls able to penetrate up to 8 cm into the seabed, although the doors of an otter trawl do create recognisable scour of the seabed (Hinz et al., 2012; Polet & Depestele, 2010; Lart, 2012; Paschen et al. 2000). The magnitude of the immediate response to fishing disturbance, cumulative effects and recovery times varies significantly according to factors such as the type of fishing gear and fishing intensity, the habitat and sediment type, and levels of natural disturbance and among different taxa (Collie et al., 2000; Boulcott et al., 2014; Kaiser et al., 2006; Hinz et al., 2009; Kaiser et al., 2001). Due to their penetrative nature and close contact with the seabed, scallop dredges cause substantial physical disruption to the seafloor by ploughing sediments and damaging organisms. The Newhaven dredges used by the UK king scallop fishery are likely to be one of the most damaging types of scallop dredge due to the effect of their long teeth, which can penetrate 3 – 10 cm into the seabed (Howarth & Stewart, 2014; Hinz et al., 2012).

Subtidal coarse sediments have a range in sensitivity to surface abrasion from not sensitive to high; subtidal sands have a range in sensitivity from not sensitive to medium; and subtidal mixed sediments have a medium sensitivity (Tillin et al., 2010). For sub-surface abrasion/penetration, subtidal coarse sediments have a range in sensitivity from low to medium; subtidal sands have a range in sensitivity from low to medium; and subtidal mixed sediments have high sensitivity (Tillin et al., 2010). The degree to which particular examples of the habitat are sensitive to surface abrasion and sub-surface abrasion/penetration will be dependent on the species present.

Changes in suspended solids (water quality) and siltation rate changes (light), including smothering, may result from physical disturbance of the sediment, along with hydrodynamic action caused by the passage of towed gear, leading to entrainment and suspension of the substrate behind and around the gear components and subsequent siltation (Sewell et al., 2007; Gubbay & Knapman, 1999; Lart, 2012; Kaiser et al., 2002; Riemann & Hoffmann, 1991; O'Neill et al., 2008; Dale et al., 2011; O'Neill & Summerbell, 2011). The quantity of suspended material, its spatial and temporal persistence and subsequent patterns of deposition will depend on factors associated with the gear (such as type/design, weight, towing speed), sediment (particle size, composition, compactness), the intensity of the activity, and the background hydrographic conditions (Sewell et al., 2007; Connor et al., 2004; Dale et al., 2011; O'Neill et al., 2008). Turbid plumes can reduce light levels and smother feeding and respiratory organs. Sediment remobilisation and deposition can affect the settlement, feeding, and survival of biota through smothering of feeding and respiratory organs. Prolonged exposure of an area to these pressures may result in changes in sediment composition, including through suspension and transport of finer material. There are also concerns over resuspension of phytoplankton cysts and copepod eggs (Kaiser et al., 2001; Sewell et al., 2007; Gubbay & Knapman, 1999; Kaiser et al., 2002; O'Neill & Summerbell, 2011).

Subtidal coarse sediments and subtidal sands are not sensitive to water clarity changes, whilst subtidal mixed sediments have a range in sensitivity to water clarity changes from not sensitive to medium (Tillin et al., 2010). For siltation rate changes (light), subtidal coarse sediments have a range in sensitivity from sensitive to medium; subtidal sands have a low sensitivity; and subtidal mixed sediments are not sensitive (Tillin et al., 2010). Where the habitat type is considered sensitive to water clarity changes or siltation rate changes (light), the degree to which particular examples of the habitat is sensitive to the pressure will be dependent on the species present.

Bycatch is associated with almost all fishing activities and is related to factors such as gear type and its design (i.e. its selectivity), the target species and effort. There are significant concerns over the impacts of bycatch on marine ecosystems including changes in population abundance and demographics of affected species and altered species assemblages and food web structures (Alverson et al., 1994; Kaiser et al, 2001). As with other benthic towed gears, discarding of fish species from demersal seine net fisheries can be significant (Polet & Depestele, 2010; ICES, 2011). These are relatively few studies of the non-fish bycatch composition for demersal seines, however, it is probably similar to that of demersal trawls e.g. crustaceans and other invertebrates, etc., although quantities of such bycatch are likely to be lower than that of other gear types such as beam trawls (Suuronen et al., 2012; ICES, 2011; Donaldson et al., 2010; Walsh & Winger, 2011). Mixed-species and shrimp/prawn demersal trawl fisheries are associated with the highest rates of discarding and pose the most complex problems to resolve (Alverson et al., 1994; Feekings et al., 2012; Catchpole et al., 2005). Benthic trawls most frequently result in bycatch of fish crustaceans and other invertebrates and less frequently turtles and birds (Gubbay & Knapman, 1999; Sewell & Hiscock, 2005; ICES, 2013; Pierpoint, 2000; Bergmann & Moore, 2001; Catchpole et al., 2005; Tulp et al., 2005). Dredging can result in bycatch of fish, crustaceans and other invertebrates, turtles, and even marine mammals (Gubbay & Knapman, 1999; Sewell & Hiscock 2005; NOAA Fisheries, 2012; Hinz et al., 2012; Craven et al., 2013). Of all the fishing gears, scallop dredges are considered to the most damaging to non-target benthic communities (MESL & NE, 2013).

Subtidal coarse sediments and subtidal sands have a range in sensitivity to removal of non-target species from not sensitive to medium, whilst subtidal mixed sediments have medium sensitivity (Tillin et al., 2010). The degree to which particular examples of the habitat is sensitive to the pressure will be dependent on the species present. In high energy locations the associated fauna tends to be well adapted to disturbance and as a result are more tolerant of fishing-related disturbance (Dernie et al., 2003; Hiddink et al., 2006). However, stable gravels often support a 'turf' of fragile species which are easily damaged by trawling and recover slowly (Collie et al., 2005; Foden et al., 2010; Hall et al., 2008).

There is a risk that abrasion/disturbance of the substrate on the surface of the seabed, sub-surface abrasion/penetration, changes in suspended solids (water quality), siltation rate changes (light), and removal of non-target species caused by mobile demersal gear (trawls, seines, and boat dredges) may not help the maintenance of favourable condition for the subtidal sands and gravels feature within West Shetland Shelf NCMPA. Even if the impacts across gear types vary, mobile demersal fishing gears are likely to have negative impacts on biological communities across the West Shetland Shelf NCMPA and these gears are not considered compatible with maintaining favourable condition for the subtidal sands and gravels feature.

Through physical impacts from gear interacting with the seabed, mobile demersal gear carries the risk of hindering the maintenance of favourable condition for the subtidal sands and gravels feature, so that extent is stable or increasing; and structure, function, quality, and the composition of characteristic biological communities are such as to ensure they remain in a condition which is healthy and not deteriorating. Accordingly, Scottish Ministers conclude that demersal trawls, seines, and boat dredges alone at current activity levels would or might hinder the conservation objectives for the West Shetland Shelf NCMPA.

3.3.2. Impacts of static demersal gear (traps/creels and anchored nets/lines) on Offshore subtidal sands and gravels

As detailed in the JNCC Marine Pressures-Activities Database (PAD) v1.5 2022, abrasion/disturbance of the substrate on the surface of the seabed can result from surface disturbance caused by contact between the pots/traps/creels and any associated ground ropes and anchors. This occurs during setting of the pots/traps/creels and/or by movement of the gear over the seabed, for example during rough weather or during retrieval. In line and set (fixed) net fishing, surface abrasion can also result from surface disturbance caused by contact between the lines or nets themselves and any footropes and anchors. This is most likely to happen during retrieval of the gear if it is dragged along the seabed before ascent, although disturbance of the seabed can occur while the gear is fishing if movement (particularly of any anchors) occurs during rough weather, for example, or otherwise. Such physical disturbance can result in epifauna, especially emergent species such as erect sponges and coral, being dislodged (including snagged on the pot, line, or net) or damaged, although there are limited studies of such effects (Lart, 2012; Polet & Depestele, 2010; Walmsley et al., 2015; Gubbay & Knapman, 1999; Sewell & Hiscock, 2005; Coleman et al., 2013; Suuronen et al., 2012; Auster & Langton, 1999). The individual impact of a single fishing operation may be slight but cumulative damage may be significant (Eno et al., 2001; Foden et al., 2010). It was recently suggested that pot fishing at lower pot densities did not have negative impacts on seafloor communities, although negative effects did occur at higher pot densities (e.g. where pot densities exceeded 15 – 25 pots per 0.25 km²: Rees et al. 2021).

Subtidal coarse sediments to have a range in sensitivity to surface abrasion from not sensitive to high; subtidal sands to have a range in sensitivity from not sensitive to medium; and subtidal mixed sediments to have a medium sensitivity (Tillin et al., 2010). The degree to which particular examples of the habitat are sensitive to surface abrasion will be dependent on the species present. Subtidal coarse sediments, subtidal sands, and subtidal mixed sediments are not considered to be sensitive to the level of abrasion caused by static demersal gears (Tyler-Walters et al., 2009).

Bycatch (i.e. discarded catch) is associated with almost all fishing activities and is related to factors such as the gear type and its design (i.e. its selectivity), the targeted species and effort. There are significant concerns over the impacts of discards on marine ecosystems, including changes in population abundance and demographics of affected species and altered species assemblages and food web structures (Alverson et al., 1994; Kaiser et al., 2001). Whilst generally considered one of the most selective gear types, pots/traps/creels are associated with bycatch, including of non-target crustaceans (berried females of target species are also considered bycatch in some fisheries, for example), fish, mammals (e.g. seals in cod pots) and potentially some bird species (ICES, 2013; Sewell & Hiscock, 2005; Königson et al., 2015). Bycatch survival rates are generally higher for pots than other fishing gear types (Suuronen et al., 2012; Seafish, 2014). However, the associated ropes can also result in entanglement of turtles and mammals (Sewell and Hiscock, 2005; Pierpoint, 2000). Although highly selective for the larger pelagic fish, longlines can cause by-catch of large and frequently long-lived species including invertebrates (Hall et al., 2000; Gubbay & Knapman, 1999; Sewell & Hiscock, 2005; Dayton et al., 1995). Anchored nets, including gill and trammel nets, can result in the entanglement and bycatch of a range of fauna including mammals, turtles, fish, elasmobranchs, crustaceans and other invertebrates and birds (Gubbay & Knapman, 1999; ICES, 2013; WWT, 2012; Žydelis et al., 2009; Pierpoint, 2000; Oliver et al., 2015), the consequences of which can be significant to species and populations (Reeves et al., 2013; Furness, 2003; Tasker et al., 2000). Ghost fishing has also been associated with lost lines and anchored nets gear (Matsuoka et al., 2005).

Subtidal coarse sediments and subtidal sands have a range in sensitivity to removal of non-target species from not sensitive to medium, whilst subtidal mixed sediments have medium sensitivity (Tillin et al., 2010). The degree to which particular examples of the habitat is sensitive to the pressure will be dependent on the species present. In high energy locations the associated fauna tend to be well adapted to disturbance and as a result are more tolerant of fishing-related disturbance (Dernie et al., 2003; Hiddink et al., 2006).

Considering the current levels of static demersal trap fishingand static demersal anchored nets/lines within the site, and information on the impacts of abrasion/disturbance of the substrate on the surface of the seabed and removal on non-target species, trap fishing is not considered to hinder the conservation objective for the sands and gravels feature of West Shetland Shelf NCMPA.

Given the evidence above, the impacts of abrasion/disturbance of the substrate on the surface of the seabed and removal of non-target species from demersal static gear (traps/creels and anchored nets/lines) alone within West Shetland Shelf NCMPA at current activity levels would not hinder conservation objectives for the subtidal sands and gravels feature, so that extent is stable or increasing; and structure, function, quality and the composition of characteristic biological communities are such as to ensure they remain in a condition which is healthy and not deteriorating. Accordingly, Scottish Ministers conclude that demersal static gear (traps/creels and anchored nets/lines) alone at current activity levels will not hinder the achievement of the conservation objectives for the West Shetland Shelf NCMPA.

3.4. Part B Conclusion

The assessment of the impact of fishing pressures at current activity levels on the subtidal sands and gravels feature of West Shetland Shelf NCMPA has indicated that mobile demersal fishing activities would or might hinder the achievement of the conservation objectives for the site. As such Scottish Ministers conclude that management measures to restrict mobile demersal gears are required within West Shetland Shelf NCMPA. Section 5 contains further details on potential measures.

Scottish Ministers conclude that the remaining static demersal fishing activities (traps/creels and anchored nets/lines), when considered in isolation and at current levels, will not hinder the achievement of the conservation objectives for the West Shetland Shelf NCMPA.