Freshwater pearl mussel

195. Adult freshwater pearl mussel are confined to freshwater environments, and there is therefore no pathway for direct effects associated with this impact. However, there is potential for indirect impacts on the larval stage of freshwater pearl mussel if Atlantic salmon (their host species) are impacted. As detailed in paragraphs 193 and 194, underwater noise in the construction phase will not lead to significant mortality or injury to Atlantic salmon and is unlikely to result in barriers to migration. Therefore, it can also be concluded that there will be no indirect impact to freshwater pearl mussel.

Conclusion

196. Adverse effects on the qualifying Annex II diadromous fish features of the River South Esk SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraphs 78 to 80) are discussed in turn below in Table 5.15   Open ▸ .

Table 5.15: Conclusions Against the Conservation Objectives of the River South Esk SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

197. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the River South Esk SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

                        Tweed Estuary SAC

Sea lamprey

198. As for Atlantic salmon, the underwater noise modelling suggested that sea lamprey within close proximity to piling operations and UXO clearance may experience injury or mortality. However, sea lamprey are also highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that the at-sea behaviour and habitat use of sea lamprey is largely unknown). Therefore, this impact is unlikely to result in significant mortality or injury to sea lamprey. Further, as presented in Table 5.4   Open ▸ , the soft start piling procedures designed in measure will allow many individuals in close proximity to piling to move away from the ensonified area and will also reduce the overall acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and the potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
199. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these would extend out the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Conclusion

200. Adverse effects on the qualifying Annex II diadromous fish features of the Tweed Estuary SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraph 90 to 92) are discussed in turn below in Table 5.16   Open ▸ .

Table 5.16: Conclusions Against the Conservation Objectives of the Tweed Estuary SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

201. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the Tweed Estuary SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase the Array alone.

                        River Tweed SAC

Atlantic salmon

202. As outlined in paragraphs 163 to 175, Atlantic salmon within close proximity to piling operations may experience injury or mortality due to underwater noise from piling or UXO clearance. However, Atlantic salmon are highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that at-sea behaviour is largely unknown). Therefore, it is unlikely that this impact will result in significant mortality or injury to the Atlantic salmon feature of this SAC. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow individuals in close proximity to piling to move away from the ensonified area and reduce the total amount of acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
203. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these may occur out to a range in the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Sea lamprey

204. As for Atlantic salmon, the underwater noise modelling suggested that sea lamprey within close proximity to piling operations and UXO clearance may experience injury or mortality. However, sea lamprey are also highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that the at-sea behaviour and habitat use of sea lamprey is largely unknown). Therefore, this impact is unlikely to result in significant mortality or injury to sea lamprey. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow many individuals in close proximity to piling to move away from the ensonified area and will also reduce the overall acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
205. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these would extend out the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Conclusion

206. Adverse effects on the qualifying Annex II diadromous fish features of the River Tweed SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraphs 99 to 101) are discussed in turn below in Table 5.17   Open ▸ .

Table 5.17: Conclusions Against the Conservation Objectives of the River Tweed SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

207. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the River Tweed SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

                        River Tay SAC

Atlantic salmon

208. As outlined in paragraphs 163 to 175, Atlantic salmon within close proximity to piling operations may experience injury or mortality due to underwater noise from piling or UXO clearance. However, Atlantic salmon are highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that at-sea behaviour is largely unknown). Therefore, it is unlikely that this impact will result in significant mortality or injury to the Atlantic salmon feature of this SAC. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow individuals in close proximity to piling to move away from the ensonified area and reduce the total amount of acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
209. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these may occur out to a range in the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Sea lamprey

210. As for Atlantic salmon, the underwater noise modelling suggested that sea lamprey within close proximity to piling operations and UXO clearance may experience injury or mortality. However, sea lamprey are also highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that the at-sea behaviour and habitat use of sea lamprey is largely unknown). Therefore, this impact is unlikely to result in significant mortality or injury to sea lamprey. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow many individuals in close proximity to piling to move away from the ensonified area and will also reduce the overall acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
211. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these would extend out the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Conclusion

212. Adverse effects on the qualifying Annex II diadromous fish features of the River Tay SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraphs 113 to 115) are discussed in turn below in Table 5.18   Open ▸ .

Table 5.18: Conclusions Against the Conservation Objectives of the River Tay SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

213. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the River Tay SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

                        River Spey SAC

Atlantic salmon

214. As outlined in paragraphs 163 to 175, Atlantic salmon within close proximity to piling operations may experience injury or mortality due to underwater noise from piling or UXO clearance. However, Atlantic salmon are highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that at-sea behaviour is largely unknown). Therefore, it is unlikely that this impact will result in significant mortality or injury to the Atlantic salmon feature of this SAC. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow individuals in close proximity to piling to move away from the ensonified area and reduce the total amount of acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
215. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these may occur out to a range in the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Freshwater pearl mussel

216. Adult freshwater pearl mussel are confined to freshwater environments, and there is therefore no pathway for direct effects associated with this impact. However, there is potential for indirect impacts on the larval stage of freshwater pearl mussel if Atlantic salmon (their host species) are impacted. As detailed in paragraphs 214 and 215, underwater noise in the construction phase will not lead to significant mortality or injury to Atlantic salmon and is unlikely to result in barriers to migration. Therefore, it can also be concluded that there will be no indirect impact to freshwater pearl mussel.

Sea lamprey

217. As for Atlantic salmon, the underwater noise modelling suggested that sea lamprey within close proximity to piling operations and UXO clearance may experience injury or mortality. However, sea lamprey are also highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that the at-sea behaviour and habitat use of sea lamprey is largely unknown). Therefore, this impact is unlikely to result in significant mortality or injury to sea lamprey. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow many individuals in close proximity to piling to move away from the ensonified area and will also reduce the overall acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
218. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these would extend out the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Conclusion

219. Adverse effects on the qualifying Annex II diadromous fish features of the River Spey SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraphs 123 to 126) are discussed in turn below in Table 5.19   Open ▸ .

Table 5.19: Conclusions Against the Conservation Objectives of the River Spey SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

220. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the River Spey SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

                        Berriedale and Langwell Waters SAC

Atlantic salmon

221. As outlined in paragraphs 163 to 175, Atlantic salmon within close proximity to piling operations may experience injury or mortality due to underwater noise from piling or UXO clearance. However, Atlantic salmon are highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that at-sea behaviour is largely unknown). Therefore, it is unlikely that this impact will result in significant mortality or injury to the Atlantic salmon feature of this SAC. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow individuals in close proximity to piling to move away from the ensonified area and reduce the total amount of acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
222. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these may occur out to a range in the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Conclusion

223. Adverse effects on the qualifying Annex II diadromous fish features of the Berriedale and Langwell Waters SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraph 133) are discussed in turn below in Table 5.20   Open ▸ .

Table 5.20: Conclusions Against the Conservation Objectives of the Berriedale and Langwell Waters SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

224. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the Berriedale and Langwell Waters SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

                        River Teith SAC

Atlantic salmon

225. As outlined in paragraphs 163 to 175, Atlantic salmon within close proximity to piling operations may experience injury or mortality due to underwater noise from piling or UXO clearance. However, Atlantic salmon are highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that at-sea behaviour is largely unknown). Therefore, it is unlikely that this impact will result in significant mortality or injury to the Atlantic salmon feature of this SAC. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow individuals in close proximity to piling to move away from the ensonified area and reduce the total amount of acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
226. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these may occur out to a range in the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Sea lamprey

227. As for Atlantic salmon, the underwater noise modelling suggested that sea lamprey within close proximity to piling operations and UXO clearance may experience injury or mortality. However, sea lamprey are also highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that the at-sea behaviour and habitat use of sea lamprey is largely unknown). Therefore, this impact is unlikely to result in significant mortality or injury to sea lamprey. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow many individuals in close proximity to piling to move away from the ensonified area and will also reduce the overall acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
228. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these would extend out the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Conclusion

229. Adverse effects on the qualifying Annex II diadromous fish features of the River Teith SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraphs 140 to 141) are discussed in turn below in Table 5.21   Open ▸ . As stated in paragraphs 140 to 141), a CAP has not yet been published for the River Teith SAC, and therefore, only the overarching conservation objectives for all qualifying species features are presented in Table 5.21   Open ▸ for Atlantic salmon and sea lamprey combined. The assessment has therefore been undertaken with regard to the available conservation objectives for the site (NatureScot, 2015).

Table 5.21: Conclusions Against the Conservation Objectives of the River Teith SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

230. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the River Teith SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

                        River Oykel SAC

Atlantic salmon

231. As outlined in paragraphs 163 to 175, Atlantic salmon within close proximity to piling operations may experience injury or mortality due to underwater noise from piling or UXO clearance. However, Atlantic salmon are highly mobile, and may only use the fish and shellfish ecology study area to pass through during migration (noting that at-sea behaviour is largely unknown). Therefore, it is unlikely that this impact will result in significant mortality or injury to the Atlantic salmon feature of this SAC. Further, as presented in Table 5.4   Open ▸ , the designed in measure of soft start piling procedures will allow individuals in close proximity to piling to move away from the ensonified area and reduce the total amount of acoustic energy entering the marine environment. In addition, the designed in measure of low order UXO disposal will reduce the noise levels and their potential for injury in the vicinity of UXO clearance operations. Overall, these two designed in measures further reduce the likelihood of injury and mortality.
232. As outlined in paragraphs 176 et seq., underwater noise during piling would result in behavioural responses in the vicinity of the Array, although these may occur out to a range in the low tens of kilometres, and thus not represent a significant barrier to migration to and from the SAC, particularly in terms of the vast availability of habitat in the North Sea and distance between the coast and the site boundary ( Figure 5.2   Open ▸ and Figure 5.3   Open ▸ ). The behavioural disturbance modelling results are also highly precautionary as they were modelled against the maximum hammer energy, which will not realistically occur over the duration of the piling programme. Further, the potential underwater noise impacts will be short term and intermittent in nature during the construction phase (i.e. piling occurring over up to 602 days over eight years). As such, there is negligible risk of disruption to migration.

Freshwater pearl mussel

233. Adult freshwater pearl mussel are confined to freshwater environments, and there is therefore no pathway for direct effects associated with this impact. However, there is potential for indirect impacts on the larval stage of freshwater pearl mussel if Atlantic salmon (their host species) are impacted. As detailed in paragraphs 231 and 232, underwater noise in the construction phase will not lead to significant mortality or injury to Atlantic salmon and is unlikely to result in barriers to migration. Therefore, it can also be concluded that there will be no indirect impact to freshwater pearl mussel.

Conclusion

234. Adverse effects on the qualifying Annex II diadromous fish features of the River Oykel SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise during construction activities. Potential effects from these activities on the relevant conservation objectives (as presented in paragraphs 146 to 148) are discussed in turn below in Table 5.22   Open ▸ .

Table 5.22: Conclusions Against the Conservation Objectives of the River Oykel SAC from Underwater Noise Generated during Piling and UXO Clearance in the Construction Phase of the Array Alone

235. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the River Oykel SAC as a result of underwater noise generated during piling and UXO clearance with respect to the construction phase of the Array alone.

5.3.2. Effects due to EMFs from Subsea Electrical Cabling

236. The LSE2 assessment during the HRA Stage One process identified that during the operation and maintenance phase, LSE2 could not be ruled out for potential effects to Annex II diadromous fish from EMFs generated by subsea electrical cables. This relates to the following sites and relevant Annex II diadromous fish features:

• River Dee SAC;

–           Atlantic salmon; and

–           freshwater pearl mussel.

• River South Esk SAC;

–           Atlantic salmon; and

–           freshwater pearl mussel.

• Tweed Estuary SAC;

–           sea lamprey.

• River Tweed SAC;

–           Atlantic salmon; and

–           sea lamprey.

• River Tay SAC;

–           Atlantic salmon; and

–           sea lamprey.

• River Spey SAC;

–           Atlantic salmon;

–           freshwater pearl mussel; and

–           sea lamprey.

• Berriedale and Langwell Waters SAC;

–           Atlantic salmon.

• River Teith SAC; and

–           Atlantic salmon; and

–           sea lamprey.

• River Oykel SAC;

–           Atlantic salmon; and

–           freshwater pearl mussel.

237. The MDS considered for the assessment of EMF is shown in Table 5.23   Open ▸ . There are no designed in measures for the Array applicable to this impact.

Table 5.23: MDS Considered for the Assessment of Potential Impacts to Annex II Diadromous Fish due to EMFs during the Operation and Maintenance Phase of the Array Alone

                        Information to support the assessment

                        Background information on EMFs

238. Effects to Annex II diadromous fish may arise due to EMFs generated from the subsea electrical cables associated with the Array as outlined in Table 5.23   Open ▸ . The conduction of electricity through subsea power cables will result in emission of localised EMFs which could potentially affect the sensory mechanisms of diadromous fish species (Centre for Marine and Coastal Studies (CMACS (2003)). This assessment also considers the impacts of EMFs from the dynamic inter-array cables in the water column ( Table 5.23   Open ▸ ).
239. EMFs comprise both the electrical fields, measured in volts per metre (V/m), and the magnetic fields, measured in microtesla (µT), millitesla (mT), milligauss (mG) or gauss. Within the North Sea, background magnetic field measurements are approximately 50 μT, and background electric field measurements are approximately 25 μV/m (Tasker et al., 2010). Subsea cables are constructed using magnetic outer sheathing materials, which can partially block the direct electrical field (E-field), meaning that the only EMFs that are emitted into the marine environment are the magnetic field (B-field) and the resultant induced electrical field (iE-field). Dynamic cables are typically double armoured to increase stability and manage weight, which may inadvertently reduce losses of EMFs (Hervé, 2021). By design, AC and DC cables typically contain three and two conductor bundles, respectively, which are superimposed and twisted around each other. This design feature creates partial self-cancellation of the total B-field (CSA Ocean Sciences Inc and Exponent, 2019, Hervé, 2021).
240. The strength of the B-field (and consequently, induced E-fields) decreases rapidly horizontally and vertically with distance from source. At the seabed, cable burial and cable protection are common industry practice measures, which can reduce EMF levels at the seabed surface as a result of field decay with distance of the seabed from the cable (Chapman et al., 2023, CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2005, Gill et al., 2009). For example, a recent study by CSA Ocean Sciences Inc and Exponent (2019) found that inter-array and offshore export cables buried between depths of 1 m to 2 m reduced the B-field at the seabed surface four-fold. For cables that were unburied and instead protected by thick concrete mattresses or rock berms, the field levels were found to be similar to those of buried cables (CSA Ocean Sciences Inc and Exponent, 2019). The same study also demonstrated that B-field levels directly over live AC inter-array cables associated with offshore wind projects ranged between 65 mG at the seabed and 5 mG and 1 m above the seabed. At lateral distances from the cables, B-fields greatly reduced at the sea floor to between 10 mG and <0.1 mG (CSA Ocean Sciences Inc and Exponent, 2019).
241. Clear differences between AC and DC systems are also apparent. The flow of electricity associated with an AC cable changes direction (as per the frequency of the AC transmission) and creates a constantly varying E-field in the surrounding marine environment (ElectroMagneticWorks Inc, 2022, Huang, 2005). Conversely, DC cables transmit energy in one direction creating a static E-field and B-field. Average B- fields of DC cables are also higher than those of equivalent AC cables (ElectroMagneticWorks Inc, 2022, Huang, 2005).
242. Overall, EMF levels in the vicinity of subsea cables are influenced by a variety of design and installation factors, including distance between cables, cable sheathing, number of conductors, and internal cable configuration.
243. While the majority of cables will be buried beneath surface sediments to a minimum burial depth of 0.4 m, up to 116 km will be dynamic cables within the water column ( Table 5.23   Open ▸ ). However, the intensity of EMF from subsea cables decreases at approximately the inverse square/power of the distance away from the cable (Hutchison et al., 2021). This attenuation is the same for buried, unburied, and dynamic cables (Hutchison et al., 2021). So, whilst EMFs from dynamic cables will be considerably higher than compared to buried cables (i.e. due to the lack of surface sediments/protection upon these), EMF levels will return to the baseline level within a few metres distance from the cable, to a maximum of a few tens of metres. Therefore, as for the buried cables at the seabed, the area of effect is highly limited in extent, particularly in the context of the fish and shellfish ecology study area as a whole and wider migration route of diadromous fish species.

                        Sensitivity of Annex II diadromous fish species to EMFs

244. EMFs may interfere with the navigational ability of some diadromous fish species. Species for which there is evidence of a response to E and/or B-fields include Atlantic salmon, sea lamprey, river lamprey, and European eel Anguilla anguilla  (CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2005). During the marine phase of their life cycles, diadromous fish species may be exposed to EMFs from the dynamic cables in the water column. EMFs emitted from these dynamic cables are likely to only be detected within a matter of metres; beyond which, baseline levels will be established (see paragraph 243). As such, impacts from EMFs from the dynamic cables are highly localised. Lamprey species possess specialised ampullary electroreceptors that are sensitive to weak, low frequency electric fields (Bodznick et al., 1981, Bodznick et al., 1983), which are hypothesised to be used for prey-detection, although further research is required in this area (Tricas et al., 2012). Chung-Davidson et al. (2008) found that weak electric fields may play a role in the reproduction of sea lamprey and it was suggested that electrical stimuli mediate different behaviours in feeding-stage and spawning-stage individuals. This study showed that migration behaviour of sea lamprey was affected (i.e. adults did not move) when stimulated with electrical fields of intensities of between 2.5 mV/m and 100 mV/m, with normal behaviour observed at electrical field intensities higher and lower than this range (Chung-Davidson et al., 2008). It should be noted, however, that these levels are considerably higher than modelled induced electrical fields expected from AC subsea cables. There is currently no evidence of lamprey responses to B-fields (Gill et al., 2010).
245. Salmonids (including Atlantic salmon) have been found to possess magnetic material of a size suitable for magnetoreception, and can use the earth’s magnetic field for orientation and direction-finding during migration (CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2010). Research in Sweden on the effects of a High Voltage Direct Current (HVDC) cable on the migration patterns of a range of fish species, including salmonids, failed to find any effect  (Westerberg et al., 2007, Wilhelmsson et al., 2010). Research conducted at the Trans Bay cable, a DC undersea cable near San Francisco, California, found that migration success and survival of chinook salmon Oncorhynchus tshawytscha was not impacted by the cable (Kavet et al., 2016). However, behavioural changes were noted when these salmonids were near the cable with individuals appearing to remain around the cable for longer periods (Kavet et al., 2016). Similarly, Yano et al. (1997) investigated the role of magnetic compass orientation in oceanic migrating chum salmon, Oncorhynchus keta, off the coast of Japan. Four chum salmon were fitted with a tag which generated an artificial B-field which produced an alternating intensity of around 6 gauss, with polarity which reversed every 11.25 minutes. The authors did not observe any effects on horizontal or vertical movements of the chum salmon when the B-field was modified (Yano et al., 1997). Further, the effects of mains frequency (50 Hz) B-fields on behaviour of captive Atlantic salmon were investigated by Armstrong et al. (2015). They found that large Atlantic salmon (62 cm to 85 cm) demonstrated no significant differences in approach, traverse or departure times associated with coils emitting a B-field of 95 µT. Post-smolts (24 cm to 41 cm in size) were exposed to three 30 minute periods of B-fields at 1.3, 11.4 and 95 µT with 30 minutes of control conditions before each treatment. There was no evidence that the numbers of post-smolts passing through the coils depended on the sequence of intensity of the B-fields. There were also no observations of unusual behaviours in association with B-fields up to 95 µT (Armstrong et al., 2015). During their marine phase, Atlantic salmon are thought to use chemoreceptors in coastal waters to locate their natal river and EMFs during offshore migrations (Gill et al., 2010). However, as Atlantic salmon are a pelagic species, the effects would be mostly perceived in shallower waters (Snyder et al., 2019).
246. Although not an Annex II species, European eel have also been suggested to use the earth’s magnetic field for navigational purposes during migration (CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2010). Studies on European eel have highlighted some limited effects of subsea cables (Westerberg et al., 2008), with evidence of direct detection of EMF through its lateral line (Moore et al., 2009). Westerberg et al. (2008) demonstrated short term changes in European eel swimming speed during migration (i.e. tens of minutes) due to exposure to AC electric subsea cables, even though the overall direction remained unaffected. Ohman et al. (2007) concluded that any delaying effect (i.e. on average 40 minutes) were not likely to impact fitness over the species’ 7,000 km migration, with little to no impact on migratory behaviour noted beyond 500 m from wind farm development infrastructure. While the research summarised in this paragraph does not focus on the Annex II diadromous fish features of the SACs assessed in this Part of the RIAA, it indicates that behavioural effects in response to EMF are limited both temporally and spatially and do not cause barriers to migration for European eel. Reasonably, these assumptions can also be inferred to Atlantic salmon and sea lamprey. 
247. These studies demonstrate that while EMFs can result in altered patterns of fish behaviour, these changes are temporary and highly localised, and are therefore not likely to represent barriers to migration or impede population health. It should be noted that although there is limited information available in the literature on the impacts and sensitivities of shellfish species to EMFs, Annex II freshwater pearl mussel would not be directly impacted by EMFs produced by electrical cabling associated with the Array given that they are a freshwater resident species. There will be no electrical cabling associated with the Array installed in any freshwater habitats, as the Array is solely located within offshore waters.