Draft Fisheries Assessment – North-West Orkney NCMPA: Fisheries management measures within Scottish Offshore Marine Protected Areas (MPAs)

3. Part B – 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 NCMPA and whether management measures may be needed for these fishing activities, 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 and pressures identified in Part A which have been included for assessment in Part B, are demersal trawls, demersal seines, boat dredges and anchored nets/lines and traps and creels, and the pressures 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); removal of target species, and smothering and siltation rate changes (light).

3.2 Fishing Activity Descriptions

3.2.1 Existing management of fishing activity within the North-west Orkney NCMPA

The NCMPA overlaps the sandeel Area 5 and 7 management units, for which a zero Total Allowable Catch (TAC) has been set and so no targeted sandeel fishery can currently take place within the region.

3.2.2 Fishing Activity within the MPA

The North-west Orkney NCMPA overlaps ICES rectangles 48E7, 48E6, 47E7, 47E6, 47E5 and sits within ICES Division 4a. The main gear types for UK vessels are traps, midwater trawls, demersal trawls and hooks and lines.

VMS-based estimates and ICES rectangle landings statistics indicate that vessels utilising static gear (traps/pots/creels) are the predominant UK vessels that operated within the site over the period 2015-2019.

For the over-12 m vessels, based on VMS data from 2015-2019, demersal trawls operate predominantly in the western part of the site, as well as along the north and eastern boundary.

3.2.3 Demersal Trawls

The aggregated gear method of demersal trawls includes the multiple gears that operated within the North-west Orkney NCMPA between 2015 and 2019. These include bottom otter trawls, multi-rig trawls, pair trawls, and other not specified bottom trawl types (Table 1).

The target species for these gear types are demersal fish, nephrops and molluscs. 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.

Based on the VMS, the highest intensity of demersal trawl activity within North-west Orkney NCMPA occurs within western edge of the site, with activity peaking at greater than 336 hours per year per grid cell between 2015-2019 (Figure 2). An area to the East of the site also showed higher level of fishing of 24-48 hours of fishing per year per grid cell between 2015-2019, as well as two small areas on the North and South side. The majority of the site has lower fishing intensity (less than 12 fishing hours per year).

Swept-Area Ratio (SAR) information averaged over the same time-period shows similar patterns of fishing intensity as the VMS data (Figure 2). The west edge of the site has the highest SAR values, being swept 5-10 times per year per grid cell between 2015-2019, and the north-east corner showing 1-5 times per year per grid cell (Figure 2). The majority of the rest of the site had low SAR values (cells swept less than once per year).

3.2.4 Demersal Seines

Both Scottish Seine, and Danish Anchor Seine were found to operate within the North-west Orkney NCMPA between 2015 and 2019 (Table 1). These seines target demersal fish. Similar pressures are exerted by the different gears used for demersal seine fishing, subsequently the aggregated gear type of ‘demersal seine’ was used to map activity across the site.

Based on the VMS, demersal seine activity within North-west Orkney NCMPA predominantly occurs in the south-west region of the site, up to a maximum of 48 hours per year per grid cell (Figure 3). There is a sparse distribution of activity occurring across the site of less than 12 hours per year per grid cell.

Swept-Area Ratio (SAR) information averaged over the same time period shows similar patterns of fishing intensity as the VMS data (Figure 3), with areas of low fishing intensity dispersed throughout the site, which were swept less than once between 2015-2019. The south-east corner of the site shows similar higher levels of activity, like the VMS, where SAR ratios show that the areas were swept two to five times between 2015-2019 and one cell in the north-east showing a SAR value of 1-2 times.

3.2.5 Boat Dredge

Fishing with the gear type towed dredge was identified during activity screening as an activity occurring within the site during the assessment period (2015-2019). Vessels utilising this gear were shown to target mollusc species.

The VMS data (Figure 4) showed that the majority of dredge activity occurred in the centre of the site and along the central southern boundary. The central region shows activity occurring predominantly at less than 12 hours per year per grid cell, with a maximum of 48 hours of activity per year per year per grid cell for some cells.

SAR information averaged over the same time period shows a similar distribution of activity, with all areas swept less than once.

3.2.6 Anchored nets/lines

Anchored net and line fishing were found to operate within the site during the assessment period (2015-2019) under gear types set gillnets and set longlines. These static gear types target demersal fish species. Similar pressures are exerted by the different gears, subsequently the aggregated gear type of ‘anchored nets/lines’ was used to map activity across the site.

VMS data (Figure 5.) shows that low levels of set net and line activity occurs within the eastern area of the site at levels of less than 12 hours per year per grid cell (average 2015-2019).

3.2.7 Traps and creels

Traps and creels were found to operate within the site during the assessment period (2015-2019). These static gear types target crustacean species.

VMS data (Figure 6) shows that the activity occurred across the majority of the site. The highest intensity of fishing, (up to an average of 168 hours per year per grid cell) was found to occur in the central region of the site. Lower levels were found across the rest of the site, and an average of less than 48 hours per year per grid cell found between 2015 and 2019.

3.2.8 Summary of fishing activity within North-west Orkney NCMPA

Fishing activities using demersal trawls, demersal seines, boat dredges, traps and creels and anchored nets/lines all occur within the North-west Orkney NCMPA.

The majority of activity undertaken is demersal static activity through traps and creels and demersal mobile through demersal trawl. Demersal trawl activity predominantly occurred at the western boundary of the site, with traps and creels in the eastern area.

Boat dredge, anchored nets and lines and demersal seine activity also occur, however these were at far lower levels than demersal trawl and traps and creels.

3.3 Fishing activity effects overview

The following sections explore the pressures associated with fishing activity (demersal mobile and demersal static) within the North-west Orkney NCMPA that were considered capable of impacting the sandeel. 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;
• Removal of target species;
• Changes in suspended solids (water clarity); and
• Smothering and siltation rate changes (light).

All five pressures, as exerted by mobile demersal fishing (trawls, seines, and boat dredges), were considered capable of impacting the sandeel feature. For static demersal fishing (anchored nets/lines and traps and creels), only abrasion/disturbance of the substrate on the surface of the seabed and removal of non-target species were considered capable of impacting the sandeel 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 feature are discussed under the aggregated fishing gear types of ‘mobile demersal gears’ and ‘static demersal gear’.

Information on the impacts of demersal trawls, demersal seines boat dredge and anchored nets/lines on the protected features is presented below and is informed by the JNCC PAD and FeAST, JNCC and NatureScot Fisheries Management Guidance document for Sandeels, and Management Options paper for North-west Orkney NCMPA.

3.3.1 Summary of impacts associated with demersal mobile gear on North-west Orkney NCMPA protected features

Demersal trawl, demersal seine and boat dredge are associated with 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; removal of target species and smothering and siltation rate changes (light) (Table 4). These are pressures to which sandeel are considered sensitive, or requiring further assessment.

In relation to the removal of target species, the Scottish Government has prohibited fishing for sandeel in all Scottish waters. The Sandeel (Prohibition of Fishing) (Scotland) Order 2024 came into force on 26 March 2024 ahead of the 2024 fishery season and will apply to all vessels (UK and EU) fishing within Scottish waters. There is little evidence regarding the sensitivity of sandeel to other demersal towed gears. The larger mesh trawl and Seine nets used to catch whitefish and nephrops do not generally catch sandeel and therefore are not expected to have any direct impact through removal of target species or abrasion/disturbance of the substrate.

There is some evidence that Scallop dredges can kill sandeel buried in the sediment (Eleftheriou & Robertson, 1992). Whilst the inshore species of sandeel explored in this study is a different species from the one on which sandeel fisheries are focused (Ammodytes marinus) and the results weren’t quantified, the authors highlighted the mortality should be taken into account when considering the possible effects that commercial dredging might have on sandeel fishing grounds. Further work from Marine Scotland Science has shown that even when equipped with a fine mesh net to sample sandeel, the efficiency is < 12% (MSS, unpublished data) and not therefore considered to pose a significant risk. Video evidence during tows shows that most sandeels escape the dredge, with the addition of the hood (fine mesh net) increasing catchability. However, there is potential for sandeels that escape dredges to be injured and subsequently die so levels of mortality could be different to levels of catchability.

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. Sandeels are reactive to disturbance near the seabed and will emerge from the sediment with the passing of fishing gear. A possible effect would be the energetic costs of repeated disturbance, i.e. from multiple fishing events, particularly during the overwintering period. This could result in effects on their survivability due to increased predation, reduced foraging, and lower reproductive success from higher energy outputs e.g. from increase burst swimming. Whilst empirical evidence is lacking, expert opinion supports this rationale.

Surface abrasion, and siltation can potentially impact sandeel indirectly. Sandeel are a burrowing species associated with sandy sediments, foraging over the sediments they inhabit. The sensitivity of sandeel to these pressures within the site relates to the species preference for sand ripple sediments, (Wright et al. 2000). The habitat within the North-west Orkney NCMPA is mixed ground type (areas of rough substrate within the areas of sediment). Data shows the site is largely comprised of offshore subtidal sands and gravels (JNCC, 2014).

Tien et al. (2017) used a model (GLMM) to examine the presence of three sandeel species A. tobianus, H. lanceolatus and A. marinus off the Dutch coast in relation to sediment characteristics (particle size), water velocity near the seabed, and to fishing effort of the beam trawl fishery targeting flatfish and shrimp. Beam trawls targeting flatfish use tickler chains which dig through the top layer of sediment to target the partially buried fish. The presence of all three species was found at lower levels of fishing effort and not at higher levels of intensity. Presence of A. marinus and A. tobianus was negatively correlated with flatfish fishing effort. This relationship was not found for the shrimp fishery for these two species and Tien et al. (2017) outline that that the shrimp fishery uses lighter gear that doesn’t dig into the seabed which may offer an explanation. No beam trawling activity was found to occur within the site and the targeted fishery for demersal trawl gear types was a mix of demersal and nephrops.

The siltation pressure identified with the demersal mobile gears within the site is classified as ‘light siltation’ (<5 cm). The predominant risk of pressure is that it may completely smother smaller species and habitats, particularly sessile organisms. As a comparatively larger, mobile species which routinely burrows 15-20 cm within sediment, it is not anticipated that sandeel will be adversely impacted from this level of siltation.

Sediment wave fields, sand banks and sand wave fields represent features under the Marine Geomorphology of the Scottish Shelf Seabed category, and are predominantly formed by the action of tidal currents. As long as current patterns and flow rates are maintained, these features are likely to be maintained over time, even if subject to physical disturbance, (Brooks, 2013). Accordingly, no impacts are associated with demersal mobile gear.

Given the evidence above, the impacts of 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; removal of target species and smothering and siltation rate changes (Light) from demersal mobile gear alone within North-west Orkney NCMPA at current activity levels would not hinder the conservation objectives for sandeel and sediment wave fields, sand banks and sand wave fields.

3.3.2 Summary of impacts associated with demersal static gear on North-west Orkney NCMPA protected features

The pressure ‘abrasion/disturbance of the substrate on the surface of the seabed’ was shown in Part A as occurring as a result of pots and trap fishing (creels) and static nets/lines, and also as pressure that the protected feature (sandeel) are sensitive to (Table 4). The pressure can result from surface disturbance caused by contact between the pots/traps or nets and any associated ground ropes and anchors. This occurs during setting of the pots/traps, or retrieval of nets and/or by movement of the gear over the seabed, for example during rough weather or during retrieval.

Surface abrasion can potentially impact sandeel indirectly. The sensitivity of sandeel to this pressure relates to the species preference for sand ripple sediment and so the pressure could impact habitat preferences and settlement, (Wright et al 2000). However, the habitat North-west Orkney NCMPA is mixed ground type (areas of rough substrate within the areas of sediment). Data shows this is largely offshore subtidal sands and gravels (JNCC, 2014) which is not considered to be sensitive to the level of abrasion caused by static demersal gear (JNCC, 2013).

Sediment wave fields, sand banks and sand wave fields represent features under the Marine Geomorphology of the Scottish Shelf Seabed category, and are predominantly formed by the action of tidal currents. As long as current patterns and flow rates are maintained, these features are likely to be maintained over time, even if subject to physical disturbance, (Brooks, 2013). Accordingly, as with demersal mobile gears, no impacts are associated with demersal static gear.

Given the evidence above, the impacts of abrasion/disturbance alone from demersal static gear within North-west Orkney NCMPA at current activity levels would not hinder the maintaining favourable condition for sandeel and sediment wave fields, sand banks and sand wave fields, so that 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 mobile gear (demersal trawl, demersal seine and boat dredge) and demersal static gear (set nets/lines and traps and creels) alone at current activity levels will not hinder the achievement of the conservation objectives for North-west Orkney NCMPA.

3.4 Part B Conclusion

The assessment of fishing pressures from demersal mobile (demersal trawl, demersal seine and boat dredge) and demersal static fishing (anchored net/line and traps and creels) activities at current level of activities on sandeel and sediment wave fields, sand banks and sand wave field features of North-west Orkney NCMPA has concluded that these will not hinder the achievement of the conservation objectives. This is supported by the JNCC and NatureScot Fisheries Management Guidance document for Sandeels, and Management Options paper for North-west Orkney NCMPA.

Scottish Minsters conclude that the fishing activities within the site, when considered in isolation and at current levels, will not hinder the achievement of the conservation objectives of North-west Orkney NCMPA. As such Scottish Ministers conclude that no further management measures are required within North-west Orkney NCMPA.