9.10. Measures Adopted as Part of the Array
60. As part of the Array design process, several designed in measures have been proposed to reduce the potential for impacts on fish and shellfish ecology (see Table 9.18 Open ▸ ). They are considered inherently part of the design of the Array and, as there is a commitment to implementing these measures, these have been considered in the assessment presented in section 9.11 (i.e. the determination of magnitude and therefore significance assumes implementation of these measures). These designed in measures are considered standard industry practice for this type of development.
Table 9.18: Designed In Measures Adopted as Part of the Array
9.11. Assessment of Significance
61. Table 9.13 Open ▸ summarises the potential impacts arising from the construction, operation and maintenance and decommissioning phases of the Array, as well as the MDS against which each impact has been assessed. An assessment of the likely significance of the effects of the Array on the fish and shellfish ecology receptors caused by each identified impact is given below.
Temporary Habitat Loss and Disturbance
Construction phase
Magnitude of impact
63. The MDS accounts for up to a total of 40.41 km2 of temporary habitat loss and disturbance during the construction phase ( Table 9.13 Open ▸ ). The represents 4.71% of the total Array fish and shellfish ecology study area. The MDS has been based on the total temporary habitat loss and disturbance as a result of the following activities in the site preparation and construction phases:
- sandwave and boulder clearance/relocation;
- installation of inter-array and interconnector cables;
- footprint of temporary offshore wet storage;
- footprint of jack up vessels used for OSP installation; and
- installation of DEAs
64. Jack-up footprints associated with installation of OSPs will result in compression of seabed sediments beneath spud cans where these are placed on the seabed. These will infill over time, although may remain on the seabed for several years, as demonstrated by monitoring studies of UK offshore wind farms (BOWind, 2008; EGS, 2011). Monitoring at Lynn and Inner Dowsing offshore wind farm showed some infilling of the footprints, although the depressions (of the order of tens of centimetres) were still visible a two years post construction (EGS, 2011). In areas where mobile sands and coarse sediments are present such as in the majority of the fish and shellfish ecology study area (refer to volume 2, chapter 8), jack-up depressions are likely to be temporary features which will only persist for a period of months to a small number of years. In less dynamic areas, jack-up depressions may be more persistent, though will not affect fish and shellfish use of relevant habitats due to these shallow depressions usually being comprised of the same sediment types.
65. With respect to cable installation, following seabed clearance (e.g. boulder and sand wave clearance) cables will be installed beneath surface sediments using one of the cable burial methods set out in Project Description (refer to volume 1, chapter 3) (e.g. ploughing, jetting, trenching etc.). A report (RPS, 2019) commissioned by The Crown Estate reviewed the effects of cable installation on subtidal sediments and habitats, drawing on monitoring reports from over 20 UK offshore wind farms. Following cable installation, sandy sediments were shown to recover quickly, with little to no evidence of disturbance in the years following cable installation (RPS, 2019). Although there was some evidence that remnant cable trenches in coarse and mixed sediments were conspicuous for several years after installation, these shallow depressions were of limited depth (i.e. tens of centimetres) relative to the surrounding seabed, and spread over a horizontal distance of several metres and therefore did not represent a large shift from the baseline environment (RPS, 2019). In muddy and muddy sand seabed habitats, remnant trenches were observed years following cable installation, although these were relatively shallow (i.e. a few tens of centimetres) (RPS, 2019). Given that the seabed sediments within the fish and shellfish ecology study area are dominated by sands and sandy gravels, as set out in volume 2, chapter 8, the results of the RPS (2019) study suggest that disturbance to these sediments is likely to be reversible.
66. The maximum footprint of temporary wet storage is up to 250,000 m2 ( Table 9.13 Open ▸ ). Wet storage may be used to optimise delivery schedules during construction. Anchors or mooring chains may be placed on the seabed in the vicinity of their final installation location so the deliver vessel can return to port. The installation vessel will then move the equipment into their final position and install. Anchors, mooring lines and any ancillary weights may also be stored in the final turbine locations ready for the integrated turbines to be towed to site and installed within their final location. Temporary wet storage would occur within the site boundary. Impacts resulting from wet storage would be temporary in nature, and the seabed is expected to recover in the same manner as described in paragraph 65).
67. Finally, if DEAs are selected as an anchoring method for floating foundations (see Anchoring Option 2 and 3 in the Project Description, volume 1, chapter 3), it is assumed that these will be lifted from the installation vessel using a crane and positioned on the seabed. The DEAs will then be pulled using a heavy lift vessel or similar, in order to embed the anchor in the seabed. It is estimated that the anchor would be pulled between 30 and 60 m during the installation process subject to further ground investigations and anchor design. This process will be undertaken in a controlled manner to ensure that DEAs are installed at the correct position and to appropriate depth. There will be up to 1,590 DEAs installed in this manner in total ( Table 9.13 Open ▸ ).
68. Activities resulting in the temporary subtidal habitat loss/disturbance will occur intermittently throughout the construction phase. The offshore construction phase which includes activities resulting in temporary habitat loss/disturbance will occur over a period of up to eight years. Once construction in a local area has been completed, this area will not be disturbed further during the construction phase. This area will start to recover immediately following cessation of construction activities in the vicinity allowing mobile species, such as sandeel and other fish and shellfish species, to repopulate the areas of previous disturbance.
69. The impact is predicted to be of local spatial extent, medium term duration, intermittent and high reversibility. The magnitude is therefore considered to be low.
Sensitivity of the receptor
Marine fish and shellfish species
70. The fish and shellfish species within the fish and shellfish ecology study area likely to be most sensitive to temporary habitat loss are those which spawn on or near the seabed sediment (e.g. herring, sandeel and elasmobranchs). Other fish species identified as IEFs in Table 9.12 Open ▸ (particularly adults) are considered less vulnerable to temporary habitat loss as they can move away from impacted areas and recolonise quickly once construction operations have ceased in the relevant area of seabed, compared to species and life history stages (e.g. juveniles) which are less mobile.
71. As shellfish (with the exceptions of some squids) tend to be less mobile than finfish, they are usually more vulnerable to habitat loss and disturbance. For example, a mark and recapture study on berried European lobster in Norway which showed that 84% of berried female specimens remained within 500 m of their release site (Agnalt et al., 2007). However, evidence seems inconsistent; research on other stocks around the world reveal limited movement for some stocks and long-distance migrations for other stocks (e.g. Campbell and Stasko, 1985; Comeau and Savoie, 2002).
73. Nephrops spawning and nursery habitats overlap with the construction operations (including cable installation) within the fish and shellfish ecology study area (Coull et al., 1998; volume 3, appendix 9.1), though habitat type within the Array is unsuitable for Nephrops (Franco et al., 2022).
74. King scallop and queen scallop have been identified as being likely to be present within the site boundary (see Table 9.12 Open ▸ ). Scallop, whilst predominantly sessile, can swim as an escape mechanism, over limited (up to 30 m) distances (Marshall and Wilson, 2008). This was observed by Howell and Fraser (1984) during a tag and release study. This response may allow improved resilience to temporary habitat loss/disturbance than other sessile organisms, by being able to avoid areas of disturbance and relocate to areas nearby. Scallop tend to aggregate as hydrographic features dictate their larval distributions (Brand, 1991). Therefore, it can be assumed that scallop populations can spawn outside the fish and shellfish ecology study area, and within unimpacted areas of the Array, as well as within suitable habitat. It is likely that scallop will continue to be recruited into the fish and shellfish ecology study area and will recover well from any disturbance due to short term temporary habitat loss.
75. Fish and shellfish species may also be indirectly affected through feeding habitat and prey items. For example, crabs and other crustaceans and small benthic fish species (as well as other benthic species; see volume 2, chapter 8) are considered important prey species for larger fish. However, since this impact is predicted to affect only a small proportion of seabed habitats in the fish and shellfish ecology study area at any one time, with similar habitats (and prey species) occurring throughout the fish and shellfish ecology study area, these impacts are likely to be limited and highly reversible. Also, habitat disturbance during the construction phase will also expose benthic infaunal species from the sediment (see volume 2, chapter 8), potentially offering foraging opportunities to opportunistic scavengers immediately after completion of works. The implications of changes in fish and shellfish prey species are also discussed for higher trophic level receptors (i.e. marine mammals and birds) in volume 2, chapter 10 and chapter 11.
76. Most fish and shellfish ecology IEFs in the fish and shellfish ecology study area are deemed to be of low vulnerability, high recoverability and local to national importance. The sensitivity of the receptor is therefore, considered to be low.
Sandeel
77. Physical disturbance to sandeel habitats could lead to sandeel mortality if individuals cannot colonise viable sandy habitats in the immediate vicinity, or where habitats may be at carrying capacity (Wright et al., 2000), beyond which, intraspecific competition would lead to less dominant specimens being excluded from the habitat. The FeAST tool shows sandeel as having a high sensitivity to ‘sub-surface abrasion/penetration’ (Wright et al., 2000) and sandeel may also be particularly vulnerable during their winter hibernation period when they are less mobile, buried in the seabed substrates. The largest component for habitat loss and disturbance during the construction phase is through the installation of inter-array and interconnector cables (25,392,000 m2 of the total 40,408,548 m2 associated with the overall construction phase). The fish and shellfish ecology study area is located over low intensity spawning and low intensity nursery grounds for sandeel ( Figure 9.4 Open ▸ and Figure 9.5 Open ▸ ) and a mix of preferred, marginal and unsuitable habitat type, with the preferred habitat types in the north-west of the fish and shellfish ecology study area. Further, only a small proportion of this maximum footprint of habitat loss/disturbance will be occurring at any one time during the construction phase, with recovery of sediments, and sandeel populations into them.
78. Short and long term monitoring studies at the Horns Rev offshore wind farm in the Baltic Sea, Denmark, have shown that offshore wind farm construction (Jensen et al., 2004) and operation (van Deurs et al., 2012) has not led to significant adverse effects on sandeel populations. Further, recovery of sandeel occurred quickly following construction operations, so recovery of sandeel populations in the fish and shellfish ecology study area would be expected following construction operations, with the rate of recovery dependent on the recovery of sediments to a condition suitable for sandeel recolonisation. Specifically, Jensen et al., (2010) found that sandeel populations mix within fishing grounds to distances of up to 28 km; therefore, some recovery of adult populations is likely following construction operations, with adults recolonising suitable sandy substrates from adjacent un-impacted habitats. Recovery may also occur through larval recolonisation of suitable sandy sediments with sandeel larvae likely to be distributed throughout the fish and shellfish ecology study area during spring months following spawning in winter/spring (Ellis et al., 2012).
80. Sandeel (and other less mobile prey species) would be impacted by temporary habitat loss, although recovery of this species is expected to occur quickly as the sediments recover following installation of infrastructure when adults can return and also via larval colonisation of the sandy sediments.
81. Sandeel are deemed to be of high vulnerability, high recoverability and of national importance. The sensitivity of sandeel is therefore considered to be medium.
Herring
82. Based on site-specific survey data the habitats present within the site boundary are unsuitable for herring spawning ( Figure 9.2 Open ▸ ), Spawning grounds have been recorded outside the site boundary in the wider fish and shellfish ecology study area based on IHLS data ( Figure 9.2 Open ▸ and Figure 9.3 Open ▸ ). There is, however, a small overlap with the herring spawning habitat and the fish and shellfish ecology study area. However, the area of herring spawning grounds affected by this impact is expected to be very limited (being limited to the stie boundary only), in the context of available favourable sediments habitat outside and across the fish and shellfish ecology study area (see section 9.7.1).
83. Herring are deemed to be of high vulnerability, medium recoverability and of regional importance. However, the sensitivity of herring to this impact is considered to be low, given the limited suitability of herring spawning habitat within the site boundary (where temporary habitat loss/disturbance effects will occur; see section 9.7.1).
Diadromous species
84. As diadromous fish species are highly mobile, they are usually able to avoid areas subject to temporary habitat loss and are only likely to encounter the fish and shellfish ecology study area during migrations to and from natal rivers on the east coast of Scotland. Habitats within the fish and shellfish ecology study area itself are not likely to be important for diadromous fish species, so any habitat loss during the construction phase is not likely to cause any direct impact upon diadromous fish species, and is not likely to affect their migrations.
85. As with fish and shellfish, indirect impacts might exist for diadromous fish, due to impacts on prey species. For example, adult sea lamprey are parasitic and known to prey on a wide range of fish species and some cetacean species (Silva et al., 2014) and sea trout on sandeel. Like marine fish, most large species would be able to avoid habitat loss effects due to their greater mobility but would recover into the areas affected following cessation of construction.
Significance of the effect
Marine fish and shellfish species
88. For sandeel, the magnitude of the impact is deemed to be low and the sensitivity is considered to be medium. The effect will, therefore, be of minor adverse significance which is not significant in EIA terms. This is largely due to the area of unsuitable habitat for sandeel, that sandeel spawning grounds within the fish and shellfish ecology area is of low intensity and because modelling shows the abundance of buried sandeel to be very low.
For herring, the magnitude of the impact is deemed to be low and the sensitivity is considered to be low. The effect will, therefore, be of minor adverse significance which is not significant in EIA terms.
Diadromous species
Secondary mitigation and residual effect
90. No secondary fish and shellfish ecology mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Operation and maintenance phase
Magnitude of impact
91. Operation and maintenance activities within the fish and shellfish ecology study area may lead to temporary subtidal habitat loss/disturbance. The MDS is for up to 51,411,500 m2 of temporary habitat loss/disturbance during the operation and maintenance phase ( Table 9.13 Open ▸ ). This equates to 5.99% of the total site boundary and therefore this represents a relatively small proportion of the fish and shellfish ecology study area. It should also be noted that only a small proportion of the total habitat loss/disturbance is likely to be occurring at any one time over the 35-year operation phase of the Array.
92. Temporary habitat loss will occur as a result of the use of jack-up usage for operation and maintenance activities (10,500 m2 per year over the 35-year lifecycle), and also due to disturbance caused by reburial of inter-array and interconnector cables (1,222,400 m2 and 236,000 m2 per year, respectively).
93. The impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. The magnitude is therefore considered to be low.
Sensitivity of the receptor
94. The sensitivity of the fish and shellfish IEFs, for both marine and diadromous species, can be found in the construction phase assessment (see paragraph 70 et seq.), ranging from low to medium sensitivity.
Significance of the effect
Marine fish and shellfish species
95. Overall, the magnitude of the impact is deemed to be low and the sensitivity of most fish IEFs (including herring) is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
96. For sandeel, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
Diadromous species
97. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.
Secondary mitigation and residual effect
98. No secondary fish and shellfish ecology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.
Decommissioning phase
Magnitude of impact
99. Decommissioning activities within the fish and shellfish ecology study area may lead to temporary subtidal habitat loss/disturbance. The decommissioning activities include the use of jack up vessels, and inter-array and interconnector cable removal, which could give up to a total of 25,435,200 m2 of habitat loss/disturbance, representing 2.9% of the total site boundary. However, the removal of cables is likely to reverse the construction phase impacts in the longer term; that is, the seabed may return to its pre-construction state.
100. The impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. The magnitude is therefore considered to be negligible.
Sensitivity of the receptor
101. The sensitivity of the fish and shellfish IEFs, for both marine and diadromous species, can be found in the construction phase assessment (see paragraph 70 et seq.), ranging from low to medium sensitivity.
Significance of the effect
Marine fish and shellfish species
102. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of most fish IEFs (including herring) is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
103. For sandeel, the magnitude of the impact is deemed to be negligible and the sensitivity is considered to be medium. The effect will, therefore, be of minor adverse significance which is not significant in EIA terms.
Diadromous species
104. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptors is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
Secondary mitigation and residual effect
105. No secondary fish and shellfish ecology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.
Long term habitat loss and disturbance
106. Long term habitat loss and disturbance may arise due to the installation and operation of the wind turbines and associated anchors and mooring systems, OSP foundations, subsea junction boxes, and the placement and presence of scour and cable protection. This impact is relevant to the construction, operation and maintenance, and decommissioning phases of the Array and may cause indirect impacts to receptors. While this assessment considers long term habitat loss, in reality the impact will be represented not by a loss of habitat, but rather a change in a sedimentary habitat and replacement with hard artificial substrates (i.e. physical change to another seabed type, as defined by MarESA). The assessment also considers where impacts to the seabed may occur over a long period of time, for example, at the touchdown point of mooring lines and dynamic cables. At these locations the results of repeated disturbance are considered to be similar to habitat loss in that it may result in an area of seabed being unavailable to benthic species. however this does not represent a change in sedimentary habitat and replacement with artificial substrates (see paragraph 109).
107. The MDS comprises the following infrastructure, as detailed in Table 9.13 Open ▸ .
- mooring lines and anchors on the seabed, and associated scour protection;
- scour protection for all small OSP jacket foundations;
- inter-array and interconnector cable protection;
- inter-array and interconnector cable crossing protection;
- Inter-array junction boxes; and
- movement of the mooring lines.
Construction, operation and maintenance phases
Magnitude of impact
108. The presence of infrastructure associated with the Array within the fish and shellfish ecology study area will result in long term habitat loss. The MDS is for up to 19,270,958 m2 of long term habitat loss representing 2.25% of the total site boundary. A total area of up to 12,416,305 m2 will be lost due to mooring lines on the seabed (46,854 m2 per foundation). It is noted that some sections of these mooring lines or cables will be buried (e.g. mooring lines/chains associated with DEAs), which would not contribute to long term habitat loss or disturbance, though the proportion to be buried cannot be quantified at this stage. As such, the approach taken is considered to be precautionary, with the assessment based on the maximum possible habitat loss presented in the MDS. Anchors on the seabed will have a total footprint area of 25,288 m2 (based on 265 wind turbine foundations of 95 m2 each). Large OSP jacket foundations will have a footprint area of 2,163 m2 (based on three large OSPs with an area of up to 382 m2 each and 12 small OSPs at up to 85 m2 each), and a footprint area of 94,814 m² will occur due to small OSP jacket foundation scour protection. The inter-array cable protection will have a footprint area of 4,889,600 m2 due to all inter-array cable protection and 944,000 m2 for the interconnector cable protection. Up to 20% of inter-array cables and up to 30% of interconnector cables are expected to require protection, causing a potential long term habitat loss of up to 977,920 m2 for inter-array cables and up to 283,200 m2 for interconnector cables (see Table 9.13). A footprint area of up to 24,000 m2 will exist due to up to 24 inter-array and interconnector cable crossings requiring protection and the inter-array junction boxes will have a total footprint area of up to 41,040 m2, based on 228 boxes with up to 180 m2 footprint area each. For the inter-array junction box scour protection, a footprint area of up to 201,552 m2 is assumed.
110. The long term loss of subtidal habitat involves a change of sediment composition in affected areas (e.g. surrounding foundations and along sections of the Array) from soft sediment habitats (sands, gravels and muds) to hard structures (foundations, cable protection and scour protection). These areas of habitat loss will be discrete, either in the immediate vicinity of foundations (i.e. foundations, mooring lines, and scour protection), or for cable protection will be relatively small isolated stretches of cable within large areas of sediment which characterise the baseline environment (i.e. soft sediments). This translates into the loss of one type of habitat and the increase of a new habitat. The implications of this are discussed in the sensitivity section (paragraph 112 et seq.) and the potential colonisation of these new substrates is presented and discussed in later assessments of LSE1 presented in this chapter (paragraph 126 et seq.). Long term subtidal habitat loss impacts will occur during the construction phase and will be continuous throughout the 35-year operation and maintenance phase.
111. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility. The magnitude is therefore considered to be low.
Sensitivity of the receptor
Marine fish and shellfish species
113. As confirmed by desk based data sources, the fish and shellfish ecology study area coincides with fish spawning and nursery habitats including plaice, lemon sole, herring, sprat, whiting, cod, hake, ling, Norway pout, haddock, sandeel, mackerel, Nephrops and elasmobranchs (Coull et al., 1998; Ellis et al., 2012; Aires et al., 2014; see Table 9.10 Open ▸ and volume 3, appendix 9.1).
114. The fish species most vulnerable to habitat loss includes sandeel and herring. Both are demersal spawning species (species which lay their eggs on the seabed), which have specific habitat requirements for spawning (e.g. sandy sediments for sandeel and coarse, gravelly sediments for herring). Long term habitat loss and disturbance is identified by the FeAST tool as the pressure ‘Physical change (to another seabed type)’ which has identified that sandeel have high sensitivity to this impact (Wright et al., 2000). As well as utilising the seabed for laying eggs, sandeel also have specific habitat requirements throughout their juvenile and adult life history. Therefore, loss or disturbance of this specific type of habitat could represent an impact on this species. However, studies at other offshore wind farms indicate that the presence of operational offshore wind farm structures will not lead to significant adverse effects on sandeel populations in the long term. For example, monitoring studies at other offshore wind farms, including Horns Rev I, located off the Danish coast, found that the presence of offshore wind farm structures has not led to significant adverse effects on sandeel (van Deurs et al., 2012; Stenberg et al., 2011). Furthermore, initial results of a pre to post construction monitoring study at the Beatrice Offshore Wind Farm have reported that in some areas of the offshore wind farm, there was an increase in sandeel abundance (BOWL, 2021). This provides additional evidence that there is no adverse effect on sandeel populations from operational offshore wind farms and suggests that these structures could benefit sandeel populations. The fish and shellfish ecology study area is located over low intensity spawning and low intensity nursery grounds for sandeel ( Figure 9.4 Open ▸ and Figure 9.5 Open ▸ ) and a mix of preferred, marginal and unsuitable habitat type, with the preferred habitat types in the north-west vicinity of the site boundary (see volume 3, annex 9.1). As described in paragraph 108, the long term habitat loss in the Array equates to up to 19,270,958 m2. As a proportion of the total site boundary, this accounts for up to 2.25%, which is a relatively small proportion in the context of available habitat (including spawning and nursery habitats) in the fish and shellfish ecology study area.
115. Habitat within the site boundary is largely unsuitable for herring spawning; this aligns with desk based sources that note the presence of spawning grounds outside the site boundary to the north west ( Figure 9.2 Open ▸ and Figure 9.3 Open ▸ ). Therefore, the area of herring spawning grounds affected by this impact is expected to be very limited, in the context of available favourable sediments habitat outside the fish and shellfish ecology study area and across the wider northern North Sea.
116. Fish assemblages also have the potential to be impacted by long term habitat loss and disturbance as a result of the operations and maintenance of offshore wind farms. For example, monitoring at some Belgian offshore wind farms have reported slight, but significant increases in the density of some common soft sediment-associated fish species (common dragonet Callionymus lyra, solenette, lesser weever Echiichthys vipera and plaice) within the offshore wind farm (Degraer et al., 2020). There was also some evidence of increases in numbers of fish species associated with hard structures, including crustaceans (including edible crab), sea bass and common squid Alloteuthis ubulate. The authors suggested that these changes could indicate that the foundations structures were being used for egg deposition (Degraer et al., 2020). The authors also noted that these effects were site-specific and therefore may not necessarily be extrapolated to other offshore wind farms, although this does indicate the presence of offshore wind farm infrastructure does not lead to adverse, population wide effects. Therefore, it is unlikely that offshore wind farms cause any drastic changes to fish assemblages in the area (Degraer et al., 2020). For further information on the impact of colonisation of hard substrates, see paragraphs 137 et seq.
117. As described in paragraphs 72 and 73, several commercially important shellfish species inhabit the fish and shellfish ecology study area, including edible crab, European lobster, Nephrops, king and queen scallop and velvet swimming crab. As most shellfish species tend to be less mobile than finfish, they are usually more vulnerable to habitat loss and disturbance, however evidence seems inconsistent (see paragraph 72 for detail). Construction has the potential to directly damage the habitats inhabited by these species, but the potential is known to exist for recovery and increased maturity of the overall population due to decreased fishing pressure following completion of construction, with no significant change in resilience (Raoux et al., 2019). Long term loss of habitat directly around the Array infrastructure represents only a very small proportion of habitat within the fish and shellfish ecology study area, and so is unlikely to cause impacts on the wider shellfish populations.
118. Nephrops spawning and nursery habitats overlap with the locations of construction operations (including cable installation) within the fish and shellfish ecology study area (Coull et al., 1998), (see volume 3, appendix 9.1). However, Nephrops have been identified as being unlikely to be present in the site boundary based on their habitat preference of mud, which is shown to be absent in site-specific surveys).
119. Long term habitat loss is predicted to affect a relatively small proportion of the habitats within the site boundary (i.e. up to 2.25% of habitats within the site boundary; refer to Table 9.13 Open ▸ ). Lobster spawning and nursery habitats also have the potential to occur within the fish and shellfish ecology study area, though the proportion of lobster spawning and overwintering habitats affected is likely to be small in the context of the available habitats in this part of the fish and shellfish ecology study area.
120. Most fish and shellfish ecology IEFs in the fish and shellfish ecology study area (refer to Table 9.12 Open ▸ ) are deemed to be of low vulnerability, high recoverability and local to national importance. The sensitivity of the receptor is therefore, considered to be low.
121. Sandeel are deemed to be of high vulnerability, high recoverability and of national importance. The sensitivity of these fish is therefore considered to be medium.
122. Herring are deemed to be of high vulnerability, medium recoverability and of regional importance. However, the sensitivity of herring to this impact is considered to be low, due to the limited suitable spawning sediments overlapping with the site boundary and the core herring spawning ground being located outside the site boundary, though within the fish and shellfish ecology study area (see Figure 9.2 Open ▸ and Figure 9.3 Open ▸ ).
Diadromous species
123. Diadromous fish species are generally considered to be less sensitive to habitat loss than other fish species, as they are highly mobile and generally able to avoid areas subject to long term habitat loss and disturbance. Diadromous species that are likely to interact with the fish and shellfish ecology study area will do so during migrations between the North Sea and the rivers designated for diadromous fish species on the east coast of Scotland (see Table 9.11 Open ▸ and volume 3, appendix 9.1). As listed in Table 9.12 Open ▸ , the diadromous species likely to migrate through the site boundary includes Atlantic salmon, sea trout and European eel. The habitats within the fish and shellfish ecology study area are not expected to be particularly important for these species and therefore long term habitat loss and disturbance during the construction and operation and maintenance phase of the Array is unlikely to cause any direct impact to the scoped in diadromous fish species (refer to Table 9.12 Open ▸ ) and would not affect migration to and from rivers.
124. As with marine fish and shellfish IEFs (see paragraph 112), indirect impacts on diadromous fish species may occur due to impacts on prey species such as to sandeel for sea trout. As outlined previously for marine species, most large fish species would be able to avoid habitat loss effects due to their greater mobility but would recover into the areas affected following cessation of construction. Sandeel are more vulnerable to the effects of habitat loss and disturbance. However, they are expected to recover quickly as the sediments recover following installation of array infrastructure and adults recolonise and also via larval recolonisation of the sandy sediments. Therefore, the indirect impacts are not expected to impact diadromous species. The impacts associated with the creation of new hard structures are presented and discussed in later assessments of colonisation of hard structures (see paragraph 137 et seq.).