1. Introduction

1. This Fish and Shellfish Ecology Technical Report provides a detailed baseline characterisation of the fish and shellfish ecology (e.g. species, communities and habitats) of the Array. The Array refers to the offshore components of Ossian, including infrastructure such as wind turbines, offshore substation platforms and inter-array/interconnector cabling. The offshore area in which the Array will be located is referred to as the ‘site boundary’. This baseline characterisation has been informed using site-specific survey data, data from third-party organisations, and the most recent desktop data and published literature available for fish and shellfish within the northern North Sea, where the site boundary is located.
2. The aim of the technical report is to provide a robust baseline characterisation of the fish and shellfish resources within a defined study area (refer to section 2) against which the potential impacts associated with the Array can be assessed. To support the impact assessment in the Environmental Impact Assessment (EIA) Report, the ecological information presented in this technical report has been used to identify a number of Important Ecological Features (IEFs). IEFs have been determined based on the conservation, ecological and commercial importance of each identified feature within the site boundary and within the fish and shellfish ecology study area, in line with published Ecological Impact Assessment guidelines (Chartered Institute of Ecology and Environmental Management (CIEEM), 2022) (refer to section 5.2).

2.             Study Area

2. Study Area

3. As fish and shellfish are spatially and temporally variable, a broad fish and shellfish ecology study area has been defined for the purposes of baseline characterisation.
4. The fish and shellfish ecology study area proposed is reduced compared to the fish and shellfish ecology study area presented in the Array EIA Scoping Report (volume 3, appendix 6.1). Consultation feedback received from Marine Directorate - Licensing Operations Team (MD-LOT, 2023) advised that though they were “broadly content with the proposed fish and shellfish ecology study area” presented in the Array EIA Scoping Report (hereafter referred to as 'Scoping Report'), “identifying a smaller study area using the recommended methods detailed in the NatureScot representation” was recommended. NatureScot advised in their Scoping Report response in relation to the fish and shellfish study area that they “advise that this is a very large area. The Applicant may wish to consider a smaller study area based on either International Council for the Exploration of the Sea (ICES) rectangles or modelled subsea noise and/or suspended sediment concentrations (SSCs) data, whichever extend furthest from the site” (MD-LOT, 2023). Therefore, the revised fish and shellfish ecology study area is based on a precautionary zone of influence of subsea noise (100 km), including the Firth of Forth, and is presented in Figure 2.1   Open ▸ .
5. The fish and shellfish ecology study area provides a wide context for the spatially and temporally variable species and populations, including diadromous fish, which are known to occur within and in the vicinity of the site boundary. This fish and shellfish ecology study area will ensure the characterisation of all fish and shellfish receptors within the area and is therefore large enough to consider all direct (e.g. habitat loss/disturbance within the site boundary) and indirect impacts (e.g. underwater noise over a wider area) associated with the Array on identified receptors.

Figure 2.1: Fish and Shellfish Ecology Study Area

3.             Baseline Methodology

3. Baseline Methodology

3.1.        Methodology

3.1. Methodology

6. A desktop review has been undertaken to inform the baseline for fish and shellfish ecology, including review of a number of peer-reviewed publications and reports from surveys undertaken to inform other project assessments. These provide information on the fish and shellfish assemblages within the fish and shellfish ecology study area. In addition, the benthic subtidal ecology site-specific survey undertaken within the site boundary in July 2022 has also been used to inform the baseline characterisation for fish and shellfish ecology. This survey is described in section 3.3.
7. The fish and shellfish ecology baseline has also been informed by the commercial fisheries baseline characterisation (volume 3, appendix 12.1) and the benthic subtidal ecology baseline characterisation (volume 3, appendix 8.1) in addition to consultation with relevant bodies.

3.2.        Desktop Study

3.2. Desktop Study

8. A detailed desktop review of existing studies and datasets was undertaken to gather information on fish and shellfish ecology within the fish and shellfish ecology study area. Table 3.1   Open ▸ summarises the studies and datasets used.

Table 3.1: Summary of Key Desktop Studies

3.3.        Site-Specific Surveys

3.3. Site-Specific Surveys

3.3.1.    Array

3.3.1. Array

9. Considering the studies and datasets available covering the site boundary and the wider northern North Sea, to characterise the baseline for fish and shellfish ecology no site-specific fish and shellfish ecology surveys have been carried out to inform the impact assessment for fish and shellfish specifically. However, Table 3.2   Open ▸ provides a summary of the 2022 site-specific benthic subtidal ecology survey, which has been used to inform the fish and shellfish ecology baseline characterisation. The sampling locations from the 2022 site-specific survey are presented in Figure 3.1   Open ▸ . Survey operations were conducted aboard the Motor Vessel (M/V) Northern Maria by Ocean Infinity; further information is available in volume 3, appendix 8.1, annex A.
10. The benthic subtidal ecology site-specific survey included combined grab and Drop Down Video (DDV) sampling at 80 sampling stations ( Figure 3.1   Open ▸ ), all within the site boundary (refer to volume 3, appendix 8.1). Samples from two stations were excluded from Particle Size Analysis (PSA) analysis, due to incomplete grab closure at S008 (meaning sample loss occurred), and a small sample recovered at S025 which was below the minimum acceptance criteria, despite multiple attempts to acquire an acceptable volume. Ten of the 80 grab stations were also sampled for sediment contaminants; full details are provided in volume 3, appendix 8.1. Site-specific epibenthic beam trawl sampling was conducted at ten of the 80 environmental stations across the site boundary ( Figure 3.1   Open ▸ ) to support characterising the epifaunal component of the benthos within the site boundary. The PSA and other sample data and observations have been used to support characterisation of the fish and shellfish ecology baseline, with the PSA data specifically informing the substrate suitability assessments for both herring Clupea harengus spawning and sandeel Ammodytidae spp. habitation. The results are presented in sections 4.1.2, 4.4.2 and 4.5.2.
11. The habitat suitability for herring and sandeel was characterised using PSA results from site-specific grab sampling and seabed imagery (supported by geophysical datasets) across the site boundary which characterised the seabed types and sediment composition (refer to volume 3, appendix 8.1). Further, species presence/absence records were also recorded from both grab samples and DDV sampling, although these should be noted as purely opportunistic and incidental data as surveys were not specifically designed to target fish and shellfish species.
12. For herring spawning habitat characterisation, samples were classified into preferred, marginal and unsuitable based on their suitability as spawning habitat using classifications from Reach et al. (2013). These classifications assigned each grab sample with a herring spawning suitability category based on the relative proportions of fines, sands and gravel. Additional data from the IHLS showing herring spawning intensity have been used, in line with the guidelines set out by Boyle and New (2018), to complement the characterisation of spawning habitats and activity for herring in the fish and shellfish ecology study area. The abundance of larvae ≤10 mm per m2 were plotted as heat maps for the years 2007 to 2016. These maps, combined with the PSA data from site specific grab sampling, were used to determine where key spawning habitats were located in the vicinity of the site boundary (refer to section 4.4, Figure 4.7   Open ▸ to Figure 4.12   Open ▸ ).
13. For sandeel habitat characterisation, a similar approach to herring was used to classify habitats into preferred, marginal and unsuitable categories within the site boundary based upon habitat suitability classifications derived from Latto et al. (2013). As for herring, these classifications are based on the proportions of fines, sand and gravel in the grab samples. Incidental sandeel observations were also collated from the site-specific benthic grab samples (refer to section 4.5, Figure 4.14   Open ▸ and Figure 4.15   Open ▸ ). Furthermore, the predicted distribution model for sandeels in the North Sea published by Langton et al. (2021) has been mapped in relation to the site boundary in order to determine areas where the probabilities of sandeel presence and density are high (refer to section 4.5, Figure 4.13   Open ▸ ).
14. Norway lobster Nephrops norvegicus (referred to as Nephrops hereafter) presence within the site boundary was assessed through abundance data collected from epibenthic trawls, as well presence/absence of individuals and/or burrows derived from DDV sampling (refer to section 4.8.6 for results).

Table 3.2: Summary of Site-Specific Surveys Undertaken to Inform Fish and Shellfish Ecology Baseline Characterisation

Figure 3.1: Site-specific Surveys Locations

3.3.2.    Fish and Shellfish Ecology Study Area

3.3.2. Fish and Shellfish Ecology Study Area

15. The results from site-specific surveys undertaken for other recent projects in the vicinity of the site boundary have also been used to inform the baseline characterisation for fish and shellfish assemblages within the fish and shellfish ecology study area. The methods engaged are summarised below and further detail is provided within the baseline characterisation in section 4 where appropriate.
16. Epibenthic beam trawl surveys were conducted in August 2020 across 15 locations within the proposed Berwick Bank Offshore Wind Farm, located 56.77 km to the south-west of the site boundary ( Figure 3.2   Open ▸ ) (SSER, 2022). In 2012, four otter trawl surveys were conducted across the Development Area for Inch Cape Offshore Wind Farm (86.90 km south-west of the site boundary) (Inch Cape Offshore Limited, 2018). In 2011, a total of 53 epibenthic trawls were conducted within the Seagreen Alpha and Seagreen Bravo Offshore Wind Farms (now referred to as Seagreen 1 Offshore Wind Farm and Seagreen 1A Project) (located 50.72 km to the south-west of the site boundary) (Seagreen Wind Energy, 2012). In 2009, a site-specific benthic survey was conducted for Neart na Gaoithe Offshore Wind Farm (located 105 km south-west of the site boundary). This benthic survey also recorded fish species within the Neart na Gaoithe study area (Mainstream Renewable Power, 2019).
17. These site-specific surveys provide useful information on the general seabed types, sediment suitability for fish spawning (specifically sandeel and herring) and/or habitat for benthic fish and shellfish species. These site-specific surveys also provide opportunistic records of small demersal fish and shellfish species present within the fish and shellfish ecology study area.

18. Site-specific data collected as part of Digital Aerial Surveys (DAS) for marine mammals and birds conducted monthly between March 2021 and February 2023 have the potential to record basking shark Cetorhinus maximus within and in the vicinity of the site boundary, however none were recorded during the survey programme therefore no data will be included within this baseline characterisation (refer to volume 3, appendix 8.1).

Figure 3.2: Location of Offshore Wind Developments with Site-Specific Data used to Characterise the Fish and Shellfish Ecology Baseline

4.             Baseline Characterisation

4. Baseline Characterisation

4.1.        Fish and Shellfish Ecology Study Area

4.1. Fish and Shellfish Ecology Study Area

4.1.1.    Desktop Study

4.1.1. Desktop Study

19. This section provides an overview of the fish and shellfish assemblages found within the fish and shellfish ecology study area. This review primarily covers fish species and communities from regional datasets including other offshore developments within the area, with some additional information on shellfish species and communities. A more detailed characterisation of key shellfish species in the fish and shellfish ecology study area, including species of commercial importance, is presented in section 4.8.
20. The fish and shellfish ecology study area is based upon a 100 km buffer zone around the site boundary within the northern North Sea, extending inshore to encompass the Firth of Forth. This area also includes much of the Forth and Tay and North East Scottish Marine Regions (SMRs); the Forth and Tay SMR is discussed in section 4.2.
21. The North Sea can be divided into three areas with associated fish assemblages defined by depths contours and broad biogeographical patterns: shelf edge and northern North Sea, central North Sea, and southern and south-eastern North Sea (Callaway et al., 2002). The northern North Sea and central North Sea fish assemblages differ significantly to the southern and south-eastern North Sea, largely due to the depth profile and water temperature differences (Teal, 2011).
22. Many fish and shellfish species of commercial importance are present within the North Sea and thus the fish abundances are dependent on fishing pressure. Many commercial and non-commercial species also hold high ecological value as prey items for other marine species (e.g. birds and marine mammals, and other fish species).
23. A range of biotic and abiotic factors are involved in the determination of fish distribution. Abiotic factors include water temperature, salinity, depth, local scale habitat features and substrate type, and biotic factors include predator-prey interactions, inter- and intra-specific competition and anthropogenic parameters such as marine and coastal infrastructure and commercial fishing intensity.
24. The site boundary is situated in ICES area IVb, and within the south-east of the northern North Sea (Marine Scotland, 2022d). The fish assemblage in the fish and shellfish ecology study area includes demersal, pelagic, diadromous and elasmobranch species. Demersal species in the area include cod Gadus morhua, haddock Melanogrammus aeglefinus, whiting Merlangius merlangus, plaice Pleuronectes platessa, lemon sole Microstomus kitt, ling Molva, saithe Pollachius virens and sandeel. Pelagic species include herring, mackerel Scomber scombrus and sprat Sprattus sprattus. Elasmobranchs (i.e. sharks, skates and rays) are also likely to be present in the vicinity of the site boundary and the wider fish and shellfish ecology study area. Species such as spotted ray Raja montagui, thornback ray Raja clavata, tope shark Galeorhinus galeus, small-spotted catshark Scyliorhinus canicula, spurdog Squalus acanthias, thorny skate Amblyraja radiata and cuckoo ray Leucoraja naevus, among others, have been observed in the fish and shellfish ecology study area (Coull et al., 1998; Daan et al., 2005; Baxter et al., 2011; Ellis et al., 2012).
25. Dominant shellfish species in the northern North Sea include pink shrimp Pandalus borealis, Nephrops, edible crab Cancer pagurus, king scallop Pecten maximus, European lobster Homarus gammarus, brown shrimp Crangon crangon, velvet swimming crab Necora puber, queen scallop Aequipecten opercularis, cockle Cerastoderma edule, mussel Mytilus edulis, common whelk Buccinum undatum (referred to as whelk hereafter), and squid (Loliginidae spp. and Ommastrephidae spp.). The distribution of lobster and crab species is highly dependent on habitat/substrate type due to habitat preferences and relatively low mobility.
26. The IBTS is a historic time series of trawl surveys in the north-east Atlantic and Baltic Seas. IBTS trawl data gathered between 2019 and 2023 have been interrogated to ascertain the most commonly recorded species and to identify whether major components of the species assemblage have shown variation within the last five years (ICES, 2022a). Data from IBTS survey area 3 have been used as they are the most spatially relevant to the fish and shellfish ecology study area ( Figure 4.1   Open ▸ ). The most commonly recorded relevant species (i.e. those considered fish and shellfish ecology receptors) between 2019 and 2023 during the IBTS were haddock, herring, whiting, common dab Limanda limanda, Norway pout Trisopterus esmarkii, sprat, Raitt’s sandeel Ammodytes marinus, lesser sandeel Ammodytes tobianus, grey gurnard Eutrigla gurnardus, European common squid Alloteuthis subulata and long rough dab Hippoglossoides platessoides (ICES, 2022a). At least nine of the overall top ten species listed above have comprised the top ten species within each survey year between 2019 and 2023, with mackerel replacing European common squid in 2022 and Nephrops replacing Raitt’s sandeel in 2023 (ICES, 2022a). These results, based on 712 hauls within the northern North Sea over a five year period, show a high level of temporal consistency for the major components of the targeted fish and shellfish assemblage, suggesting that these species are a good indicator of characteristic species within the fish and shellfish ecology study area.
27. IBTS data for 2021, 2022 and 2023 showed low abundances of cod, with only tens of individuals, mostly juveniles of age class 1 or 2, recorded per hour trawled. Plaice also showed low abundances within the northern North Sea, with IBTS data indicating abundances of tens individuals regularly recorded per hour of trawling (ICES, 2022a). No obvious differences in abundance associated with season or age distribution of individuals was observed in the 2021 to 2023 data.
28. Herring abundances within the IBTS are high, with thousands of individuals recorded per hour trawling. Herring abundance is also seasonal, with higher numbers of individuals evident in catches at the end of the year (Q3) than at the start of the year (Q1). The IBTS data showed a marked increase specifically in adult herring abundance during Q3, which supports existing literature on herring spawning seasons, as the influx of adult herring individuals in Q3 coincides with the spawning season (refer to section 4.4 for further information) (ICES, 2022a).
29. Average recorded abundances of mackerel were low during 2022 and 2023 Q1 in comparison with 2021 Q1, however higher abundances were recorded during Q3 (2022 only). This suggests that presence of mackerel in the northern North Sea can vary annually and can be sporadic, as shown by a particular haul capturing over 246,000 mackerel per hour trawled, with other hauls recording very few or no mackerel (ICES, 2022a).
30. Sandeel, which are a crucial forage fish for many other species, are one of the most abundant species in the North Sea, accounting for approximately 25% of fish biomass (Christensen et al., 2013). Raitt’s sandeel featured in the top ten species recorded between 2019 and 2022, although it’s worth noting that a full year of survey data for 2023 is not yet available, therefore the overall composition of most abundant species may change following further sampling in Q3 into Q4 (ICES, 2022a). Further information on sandeel is provided is section 4.5.
31. Sprat have relatively high abundance, where thousands of individuals were frequently recorded per hour trawled. However, similar to mackerel, the abundances recorded were found to be quite sporadic, with low numbers being recorded frequently. While there are no obvious differences in seasonal distribution of individuals recorded, a decrease in abundances of age five fish was recorded in 2021 and 2022 (ICES, 2022a).
32. Whiting are highly abundant within the northern North Sea. IBTS data for 2021, 2022 (Q1 and Q3) and 2023 (Q1) showed abundances as high as 8,000 individuals per hour trawled. Notably, juvenile whiting (up to two years old) were, on average, the highest abundances recorded in Q1 and Q3 trawls (ICES, 2022a). Whiting is one of the most widespread and numerous species found in the North Sea but is also found across the North-East Atlantic and other European seas (Cefas, 2001). Whiting are most commonly found in depths of 30 m to 100 m, predominantly on mud and gravel bottoms, but also on sand and rock where whiting feed on crustaceans, small fish and molluscs. After the first year, whiting migrate further offshore (FishBase, 2022a).
33. Many of these fish and shellfish species have high ecological value as prey species for marine mammals and seabirds (e.g. sandeel, herring, mackerel and sprat) as well as being of high importance for commercial fisheries (e.g. European lobster, edible crab, king scallop and squid) (refer to volume 3, appendix 8.1).

Figure 4.1: Areas Surveyed in the North Sea IBTS (Source: ICES, 2013)

4.1.2.    Site-Specific Surveys

4.1.2. Site-Specific Surveys

34. As outlined in section 3.3, epibenthic beam trawl sampling was conducted at ten locations within the benthic subtidal ecology survey area ( Figure 3.1   Open ▸ ).
35. A total of 16 fish species were observed in the epibenthic trawls, with long rough dab being the most abundant followed by plaice, common dab, Norway pout, Raitt’s sandeel, lemon sole and grey gurnard. Other species recorded in lower abundances were pogge Agonus cataphractus, poor cod Trisopterus minutus, haddock, cod, transparent goby Aphia minuta, sand goby Pomatoschistus minutus, scaldfish Arnoglossus laterna, Lotidae spp. and Argentinidae spp. (refer to volume 3, appendix 8.1, annex A). Other common species known to occur within the fish and shellfish ecology study area may not have been identified through site-specific surveys within the site boundary due to the sampling method. Epibenthic trawls do not target pelagic species or large demersal species due to their low headline height and ground contact, and slow towing speed, however these have been fully characterised via desktop data sources, including survey data from the IBTS. Shellfish recorded during site-specific surveys (including trawl surveys) are discussed in section 4.8.
36. Fish species observed in DDV or caught in grab samples within the site boundary are listed Table 4.1   Open ▸ .

Table 4.1: Notable Fish Species Recorded in DDV/Grab Samples

4.2.        Forth and Tay Scottish Marine Region

4.2. Forth and Tay Scottish Marine Region

37. The Forth and Tay SMR is located in the Firth of Forth 70.68 km south-west of the site boundary. Other offshore wind farm developments, either in construction or in planning stages, exist within and in the vicinity the Forth and Tay SMR, such as the Inch Cape, Neart na Gaoithe, Seagreen 1, Seagreen 1A Project and Berwick Bank Offshore Wind Farms ( Figure 3.2   Open ▸ ).
38. Several species of commercial and ecological importance are known to be present across and in the vicinity the Forth and Tay SMR including cod, lemon sole, herring, mackerel, plaice, sandeel, saithe, sprat, spotted ray, spurdog, tope shark and whiting. The Forth and Tay SMR hosts important populations of shellfish species including Nephrops, European lobster, edible crab, velvet swimming crab and squid.
39. An epibenthic beam trawl survey was undertaken within the Berwick Bank Offshore Wind Farm, located 56.77 km west of the site boundary and a total of 553 bony fish across 21 taxa were recorded. Common dab was the most abundant species (n=167), followed by long rough dab, lesser sandeel, pogge and gobies Pomatoschistus spp. In addition, cod, lemon sole, plaice, anglerfish and bearded rockling Enchelyopus cimbrius were also recorded at very low abundances (SSER, 2022).
40. An epibenthic trawl survey undertaken within the boundary of the Seagreen 1 Offshore Wind Farm and 1A Project, located 50.72 km west from the site boundary, recorded pogge, common dab, Lozano’s goby P. lozanoi, Norway goby P. norvegicus, lesser sandeel, butterfish Pholis gunnellus, Norwegian topknot Phrynorhombus norvegicus, reticulated dragonet Callionymus reticulatus, common dragonet C. lyra, lemon sole and bull rout Myoxocephalus scorpius in at least 50% of the trawls. Common dab, gobies and lesser sandeel were the most abundant species. Other species observed are smooth sandeel Gymnammodytes semisquamatus and greater sandeel Hyperoplus lanceolatus, one elasmobranch species, the cuckoo ray, and commercial species such as plaice, whiting, cod, and red gurnard Chelidonichthys cuculus (Seagreen Wind Energy Ltd., 2012; 2019).
41. Otter trawl surveys conducted in 2012 for Inch Cape Offshore Wind Farm (86.90 km from the site boundary) recorded 30 species of fish and 20 macro-invertebrates (Inch Cape Offshore Limited, 2018). Fish species included 1,194 sprat, 161 herring, and 15 cod (Inch Cape Offshore Limited, 2018). A site-specific benthic characterisation survey undertaken in 2009 for Neart na Gaoithe Offshore Wind Farm (105 km from the site boundary) recorded several fish species such as cod and flatfish (common dab, long rough dab, and plaice) (Mainstream Renewable Power, 2019).
42. The results of site-specific surveys presented in paragraphs 39 to 41 are consistent with observations from the benthic site-specific survey of the site boundary (section 4.1.2) and support the characterisation of fish and shellfish assemblages presented herein for the fish and shellfish ecology study area.
43. Due to the nature of the surveys undertaken, which capture only a snapshot of mobile species at the time of surveying, it is expected that further species will be present within both the site boundary and the fish and shellfish ecology study area, using the area for a variety of purposes including foraging, shelter, spawning and nursery. Information from the above desktop study has been used to support broader characterisation beyond the direct observations listed herein, and to ensure that a comprehensive and robust baseline is provided. Further information regarding the presence of mapped spawning and nursery grounds within the fish and shellfish ecology study area is presented in section 4.3.

4.3.        Spawning and Nursery Grounds

4.3. Spawning and Nursery Grounds

44. Spawning and/or nursery grounds for fish and shellfish species have been identified overlapping the fish and shellfish ecology study area. Coull et al. (1998) first spatially mapped the spawning/nursery areas of key fish and shellfish species in British waters based on larvae, egg and benthic habitat survey data and Ellis et al. (2012) reviewed it for a set of fin fish and elasmobranch species in the UK waters. Due to the age of the Coull et al. (1998) study, the updated areas of high and low intensity spawning and nursery grounds provided in Ellis et al. (2012) are used here unless data was not re-assessed. It is worth noting that the Ellis et al. (2012) spawning grounds are considered of lower resolution than those presented in Coull et al. (1998), due to being extrapolated as half ICES statistical rectangles rather than actual mapped densities. Additional information from Aires et al. (2014) was used to provide further understanding of nursery areas. This was evidenced by aggregations of “0 group fish” (fish in the first year of their lives) and confirmed by models of species distributions based on species observations and abundance along with environmental data (Aires et al., 2014). The outputs of this process are recommended for use as a guide for the most likely locations of aggregations of “0 group fish”.
45. Based on the above data sources, there is a spatial overlap between the site boundary and spawning grounds for seven species of fish and shellfish and nursery grounds of 16 species. It should be noted that mapped spawning and nursery grounds do not represent a fixed area within which spawning and nursery activities occur. The boundaries and ranges for such activities are continually changing and subject to spatial and temporal variation within and outside the mapped grounds and seasons.
46. Spawning grounds that are present within the fish and shellfish ecology study area and overlap with the site boundary include high intensity spawning grounds for sandeel, low intensity spawning grounds for cod, whiting and plaice and un-determined intensity spawning grounds for lemon sole, Norway pout and sprat ( Table 4.2   Open ▸ , Figure 4.2   Open ▸ to Figure 4.5   Open ▸ ). Mapped herring spawning grounds of unspecified intensity are also located 0.62 km from the north-west and 10.31 km from the south-west boundary of the site boundary ( Figure 4.3   Open ▸ ). The species with spawning and/or nursery grounds which overlap with the site boundary are summarised in Table 4.2   Open ▸ (spawning and nursery intensity is specified where available).
47. Mapped low intensity nursery grounds for 11 species are also found to overlap with the site boundary, including for anglerfish, blue whiting Micromesistius poutassou, European hake Merluccius merluccius, ling, mackerel, spotted ray and spurdog, and unspecified intensity nursery grounds are present for haddock, lemon sole, sprat, and Norway pout ( Table 4.2   Open ▸ , Figure 4.2   Open ▸ to Figure 4.5   Open ▸ ). Low intensity nursery grounds for tope shark and common skate Dipturus batis are also located a minimum of 10.31 km of the north-west boundary of the site boundary ( Figure 4.6   Open ▸ ).
48. Spawning and nursery habitats are often influenced by seabed substrate characteristics. As such, site-specific information on sediment composition can be useful to characterise spawning and nursery habitats and have been utilised to support characterisation of herring spawning and sandeel habitats in section 4.4 and section 4.5, respectively.
49. Subtidal benthic sediments across the site boundary were found to have limited variation and ranged from muddy sand to sandy gravel, with muddy sand (32% of samples), sand (24%) and slightly gravelly sand (18%) representing the three most common sediment types reported (refer to volume 3, appendix 8.1). Sediment samples with greater than 10% mud content were only found in the south-east section of the site boundary defined as areas of muddy sand and gravelly muddy sand. The sediments within the north-west of the site boundary were dominated by sand and slightly gravelly sand, with areas of gravelly sand.

Table 4.2: Key Species with Spawning and Nursery Grounds which Overlap with the Site Boundary[1]

50. The main spawning periods of key species which have spawning grounds overlapping the site boundary are presented in Table 4.3   Open ▸ .

Table 4.3: Main Spawning Periods for Key Fish Species with Spawning Grounds which Overlap with the Site Boundary[2]

Spawning periods are marked with an X, peak spawning periods marked with an O.

*Buchan stock

51. Anglerfish are commonly found in deeper waters along the continental shelf and slope with adults occurring offshore and juveniles occasionally occurring in coastal waters. Despite limited data on the spawning grounds of anglerfish, they are believed to spawn in deep waters along the continental slope’s edge (Hislop et al., 2000, 2001; Arkhipov and Mylnikov, 2002; Laurenson, 2006). Therefore, anglerfish are not expected to spawn within or in the vicinity of the site boundary. However, low intensity nursery grounds for anglerfish have been identified to overlap with the site boundary (Ellis et al., 2012) ( Figure 4.2   Open ▸ ) and the occurrence of nursery grounds are further supported by outputs from Aires et al. (2014) where the presence of “0 group” anglerfish was detected in the fish and shellfish ecology study area and in the vicinity of the site boundary.

52. While adult blue whiting and European hake have spawning grounds in the North Atlantic, juveniles have been recorded in the fish and shellfish ecology study area and mapped nursery grounds of low intensity are identified to overlap the site boundary for both species (Coull et al., 1998; Ellis et al., 2012) ( Figure 4.2   Open ▸ ). The presence of nursery grounds for European hake is further supported by Aires et al. (2014), however, these areas are not supported for blue whiting where the presence of “0 group” aggregations was not detected in the south of the northern North Sea.

53. Cod is a common species throughout the North Sea with widespread spawning areas of low intensity occurring between January and April with a peak in February and March. Widespread nursery grounds are also present throughout the North Sea with high intensity nursery areas mapped in coastal areas, including the Firth of Forth (Coull et al., 1998; Ellis et al., 2012). Therefore, the site boundary overlaps with mapped high intensity nursery grounds and low intensity spawning grounds ( Figure 4.2   Open ▸ ) for cod. Spawning behaviour involves courtship in demersal environments typically consisting of sandy sediments and boulders (Grabowski et al., 2012), followed by the release of buoyant eggs into the water column (Hutchings et al., 1999). The presence of nursery grounds for cod is further supported by Aires et al. (2014).
54. For haddock, no mapped spawning grounds overlap with the site boundary, however an unspecified intensity nursery ground does show overlap (Coull et al., 1998) ( Figure 4.3   Open ▸ ). Similar to cod, haddock have a demersal courting period followed by pelagic egg release and larval phases (Casaretto and Hawkins, 2012), feeding on plankton before juveniles move down towards the seabed to exploit demersal prey resources, including small crustaceans and fish. The presence of haddock nursery grounds is supported by outputs from Aires et al. (2014) and may suggest higher intensity nursery grounds within the site boundary and in its vicinity than specified by Coull et al. (1998).
55. The site boundary lies in low intensity nursery grounds for herring with higher intensity nursery grounds mapped in coastal waters, approximately 10.31 km west of the site boundary (Ellis et al., 2012) ( Figure 4.3   Open ▸ ). The locations and intensity of herring nursery grounds are further supported by Aires et al. (2014). Herring show temporal inter-population variation in spawning activities but generally the Buchan stock (which occurs within the fish and shellfish ecology study area) spawn between August and September in inshore waters with mapped grounds located 0.62 km to north-west boundary of the site boundary ( Figure 4.3   Open ▸ ). A further review of herring spawning is presented in section 4.4.
56. Ling have been found to spawn in the Irish Sea and Bristol Channel between March and July with their main nursery areas further offshore in the North Atlantic but not in the North Sea (Ellis et al., 2012). However, mapped low intensity nursery grounds overlap with the site boundary (Ellis et al., 2012) ( Figure 4.3   Open ▸ ). Primary nursery grounds are difficult to establish due to a lack of data and poor success with trawl surveys, therefore mapped nursery grounds relate to the presence of secondary nursery grounds, based on individuals of less than 49 cm in length which are widely considered immature (Ellis et al., 2012). The largest catches of immature ling are generally from deeper waters.
57. Spawning of lemon sole occurs between April and September, with no defined peak period (Smith, 2014), although evidence exists of spawning in October to November dependent on stock and location (Geffen et al., 2021), with lemon sole utilising their preferred benthic habitats for spawning (Hinz et al., 2006). There are mapped nursery and spawning grounds of unspecified intensity for lemon sole which coincide with much of the site boundary ( Figure 4.3   Open ▸ ).

58. Mackerel have low intensity nursery grounds which overlap with the site boundary (Ellis et al., 2012), with no spawning grounds identified within or in proximity to the site boundary ( Figure 4.4   Open ▸ ). Mackerel spawning behaviour involves the release of eggs into the water column, where fertilisation also occurs (Walsh and Johnstone, 2006), indicating a low level of reliance on sedimentary habitats for spawning. The presence of mackerel nursery grounds is not supported by outputs from Aires et al. (2014), with no modelled observations of “0 group fish” on the east coast of Scotland.
59. Mapped plaice spawning and nursery grounds of low intensity coincide with the site boundary (Ellis et al., 2012). Spawning activities take place over the winter with peak spawning in January and February and each female producing up to half a million eggs which drift passively in the plankton (Ruiz, 2007). Once the larvae reach a suitable size for settlement, they metamorphose into their asymmetric body shape. As juveniles, they inhabit mostly shallow water, including tidal pools (Schreiber, 2013). In their second year they move into deeper water and are mostly found in a depth range of 10 m to 50 m. Plaice use coastal and estuarine habitats as nurseries, and these low intensity nursery grounds overlap with the site boundary (Ellis et al., 2012) ( Figure 4.4   Open ▸ ). The presence of low intensity nursery grounds in inshore waters is further supported by Aires et al. (2014).
60. Sandeel spawn during winter months across the majority of the North Sea with nursery grounds spanning over a similar area due to the demersal egg stage and sediment preferences for habitation throughout their life cycle (Ellis et al., 2012). The site boundary coincides with low intensity spawning and nursery grounds ( Figure 4.4   Open ▸ ), however mapped high intensity spawning grounds are located 10.31 km north-west of the site boundary at the closest point. A further review of the potential distribution of sandeel grounds is presented in section 4.5.
61. Sprat nursery and spawning grounds of unspecified intensity partially overlap with the site boundary (Ellis et al., 2012), with the nursery areas coinciding with the north-west section of the site boundary and spawning grounds (occurring mostly from May to June but extending until August) encompassing the majority of the site boundary ( Figure 4.4   Open ▸ ). The presence of sprat nursery grounds is only slightly supported by outputs from Aires et al. (2014), with aggregations of “0 group fish” seemingly limited to areas further inshore, outside of the site boundary.
62. The site boundary is located in mapped whiting spawning grounds of low intensity and nursery grounds of high intensity ( Figure 4.6   Open ▸ ). Low intensity nursery areas overlap with the eastern tip of the site boundary (Coull et al., 1998; Ellis et al., 2012) ( Figure 4.6   Open ▸ ). Whiting spawn across multiple months from February to June with no peak in the spawning activities. Spawning is not thought to be substrate dependent as eggs are released into the water column. For example, a recent study demonstrated that this species showed high plasticity in spawning ground selection with extensive areas of the North Sea appearing suitable (González-Irusta and Wright, 2017). After the eggs hatch, the larvae drift in surface waters for a year, and then move closer to the seabed as juveniles. The presence of whiting nursery grounds is supported by outputs from Aires et al. (2014).
63. Norway pout spawn from January to May with a peak in February and March in the northern North Sea and off the west coast of Scotland, with the mapped nursery grounds spanning a similar area. Based on Coull et al. (1998) only, the site boundary overlaps with mapped low intensity spawning grounds and unspecified intensity nursery grounds ( Figure 4.5   Open ▸ ).
64. Two species of elasmobranch, the spotted ray and spurdog, have mapped low intensity nursery grounds which overlap the site boundary (Ellis et al., 2012) ( Figure 4.5   Open ▸ ). Although spawning activities are expected to broadly occur in similar areas as nursery grounds, spawning grounds have not been defined due to insufficient data (Ellis et al., 2012).
65. Mapped nursery grounds of low intensity for the common skate and tope shark, are located 10.31 km to the west of the site boundary (Ellis et al., 2012) ( Figure 4.6   Open ▸ ). Spawning grounds have not been defined due to insufficient data (Ellis et al., 2012), but tope shark, as a viviparous species, are thought to spawn throughout the year with gravid females captured year-round.
66. The spawning or nursery grounds of saithe do not coincide with the site boundary, although nursery grounds of unspecified intensity are located within the fish and shellfish ecology study area off the coast of Aberdeen, 48.13 km west from the site boundary ( Figure 4.6   Open ▸ ) (Coull et al., 1998).
67. Coincidental spawning and nursery grounds of unspecified intensity for Nephrops are located within the fish and shellfish ecology study area but do not overlap the site boundary ( Figure 4.6   Open ▸ ). Mapped grounds are located a minimum of 45.94 km to the north-west, west and south of the site boundary and extend along much of the coast of the Firth of Forth (Coull et al., 1998). Shellfish species are further discussed in section 4.8.

Figure 4.2: Spawning and Nursery Areas Overlapping with the Site Boundary: Anglerfish, Blue Whiting, Cod and European Hake (Source: Coull et al., 1998 and Ellis et al., 2012)

Figure 4.3: Spawning and Nursery Areas Overlapping with the Site Boundary: Haddock, Herring, Ling and Lemon Sole (Source: Coull et al., 1998 and Ellis et al., 2012)

Figure 4.4: Spawning and Nursery Areas Overlapping with the Site Boundary: Mackerel, Plaice, Sandeel and Sprat (Source: Coull et al., 1998 and Ellis et al., 2012)

Figure 4.5: Spawning and Nursery Areas Overlapping with the Site Boundary: Whiting, Norway Pout, Spotted Ray and Spurdog (Source: Coull et al., 1998 and Ellis et al., 2012)

Figure 4.6: Spawning and Nursery Areas in Proximity to the Site Boundary: Common Skate, Tope Shark, Nephrops and Saithe (Source: Coull et al., 1998 and Ellis et al., 2012)

4.4.        Herring

4.4. Herring

4.4.1.    Desktop Study

4.4.1. Desktop Study

68. Herring are a commercially important pelagic fish in the North Sea which are targeted in the vicinity of the site boundary. However, the herring stock collapsed entirely in the 1970s as a consequence of overfishing (Scottish Herring, 2023). Since then, stocks have shown signs of recovery supported by a herring recovery plan implemented for the North Sea in 1996 and a ban on discards for pelagic fisheries, including for herring, from 2015. Active management is however still required to avoid a recurrence of the collapse (Dickey-Collas et al., 2010).
69. Herring are listed on the Scottish Biodiversity List (SBL) and as a Scottish Priority Marine Feature (PMF) and are therefore considered a high priority species for conservation actions in Scotland (Fauchald et al., 2011; Casini et al., 2004). Herring also plays an important ecological role as they are a key prey species for numerous fish, marine mammals and birds.
70. Herring populations in the North Sea are divided into three stocks during the breeding season with their own spawning and nursery grounds and migration routes (Daan et al., 1990; Coull et al., 1998). The Buchan/Shetlands stock spawns off the Scottish and Shetlands coasts in August and September, the Banks/Dogger stock spawns in the central North Sea from August to October and Southern Bight/Downs stock spawns in the English Channel between November and January. The Buchan/Shetlands stock off the coast of Scotland is the closest to the site boundary and the fish and shellfish ecology study area. The stock’s spawning and nursery grounds are presented in Figure 4.3   Open ▸ .
71. Herring nursery grounds are widespread across the entire North Sea and the west coast of Scotland with higher intensity grounds occurring in coastal waters (Ellis et al., 2012) where post larval juveniles that are yet to reach sexual maturity remain to feed. Later, they migrate further offshore where they feed until reaching sexual maturity (ICES, 2006).
72. Spawning for herring usually takes place in shallow areas between approximately 15 m and 40 m depth. Female herring lay eggs once a year in a single batch, with inter-stock variations on number, size and weights of the eggs (Cefas, 2001). For example, a 28 cm female from the Buchan/Shetlands stock could produce approximately 67,000 eggs per year, whereas a similarly sized individual from the Southern Bight/Downs stock (English Channel) could produce approximately 42,000 (Barreto and Bailey, 2014). The sticky eggs are deposited on a variety of sediments from coarse sand and gravel to shells and small stones, although gravel has been suggested as their preferred spawning habitat. Muddy sediments are considered unsuitable for herring spawning as the fine particles can stick to the eggs and block the pores thus increasing egg mortality via asphyxiation, resulting from the prevention of oxygen transfer through the pores. After incubating for between one and three weeks (water temperature dependent), autumn-spawned herring larvae become pelagic and drift in the plankton from the western North Sea to the eastern North Sea using water currents (Dragesund et al., 1980). Larvae using the Moray Firth as a nursery ground originate from west Scotland and larvae using the Firth of Forth have unclear origins (Department of Energy and Climate Change (DECC), 2004). The pelagic larvae will feed on fish eggs, copepods, euphausiids and juvenile sandeels (Last, 1989). The specific substrates on which herring spawn make herring particularly sensitive to impacts from habitat loss and disturbance. In addition, herring are considered hearing specialists with an increased sensitivity to underwater noise and are therefore vulnerable to injury or disturbance from activities which generate underwater noise, such as pile driving (refer to volume 3, appendix 10.1).

4.4.2.    Site-Specific Surveys

4.4.2. Site-Specific Surveys

73. Herring spawning grounds are most accurately mapped using a combination of herring larval data and particle size data, as recommended by Boyle and New (2018). In order to characterise herring spawning habitats in the vicinity of the site boundary, these two factors have been considered to accurately determine where the key herring spawning ground for the Buchan stock are located, following the Boyle and New (2018) guidelines. That is, the area where herring are known to spawn most frequently, noting that there is some natural variability in spawning.

                        Particle size data

74. As outlined in section 3.3, site-specific survey data were collected in 2022 and, alongside desktop studies, were used to assess the extent of suitable spawning habitat for herring within the site boundary. PSA was undertaken on the sediment samples collected which allowed classification of the sediment types according to Reach et al. (2013), as described in Table 4.4   Open ▸ . These classifications were originally developed for the marine aggregates industry, drawing on work from Greenstreet et al. (2010a) investigating spatial interactions between the aggregate application areas and herring spawning habitat.

Table 4.4: Herring Potential Spawning Habitat Sediment Classifications Derived from Reach et al. (2013)

75. Habitat suitability classifications for herring spawning, based on site-specific data, illustrated that the overwhelming majority (95%) of the site boundary has unsuitable sediment composition for herring spawning. Just four stations out of 78 within the site boundary were considered suitable for herring spawning (two preferred and two marginal) ( Table 4.4   Open ▸ ). These stations were sparsely distributed in the north-west and centre of the site boundary (see volume 3, appendix 8.1).
76. Figure 4.7   Open ▸ illustrates site-specific survey data alongside EMODnet seabed substrate data. The EMODnet seabed substrate data can also be used to assign habitat suitability for herring spawning, showing sandy gravel (between 30% and 80% gravel and a sand:mud ratio above 9:1) and gravel (above 80% gravel) as preferred spawning habitat and gravelly sand (between 5% and 30% gravel and a sand:mud ratio above 9:1) as marginal spawning habitat. Where no shading is present in Figure 4.7   Open ▸ , the habitat in that area is unsuitable for herring spawning. Overall, the results from the site-specific surveys data align with EMODnet seabed substrate data with the site boundary being encompassed by unsuitable habitat for herring to spawn. Preferred habitats are located directly north of the site boundary, in line with spawning grounds from Coull et al., (1998).
77. It is worth noting that the EMODnet seabed substrate data is of lower resolution and accuracy than the results of the site-specific survey data, due to interpolation between known data points, but provides an overall broadscale picture of the surrounding substrate within the region.
78. Figure 4.7   Open ▸ also shows the wider area comprising the Buchan Stock spawning habitat. This shows more extensive areas of marginal spawning habitat to the north of the site boundary (0.62 km away), coinciding with the area mapped by Coull et al. (1998) and a smaller area towards the south (87.45 km away). These patterns in sediment composition are considered in the context of herring larval abundances, as discussed in paragraph 80.
79. Figure 4.8   Open ▸ expands on the site-specific data presented in Figure 4.7   Open ▸ , as it includes results of PSA conducted on sediment samples obtained from the OneBenthic Portal in the fish and shellfish ecology study area outside of the site boundary (Cefas, 2019a). Of the 669 samples obtained from the OneBenthic Portal, 559 were assessed as unsuitable, 53 as marginal, and 57 as preferred spawning habitat.

Figure 4.7: Herring Spawning Habitat Preference Classifications from EMODnet and Site-specific Survey Data

Figure 4.8: Herring Spawning Habitat Preference Classifications from EMODnet and Spawning Sediment Classifications from the Site-Specific Survey Data and from the OneBenthic Portal

                        International herring larvae survey data

80. Herring spawning grounds can also be identified through monitoring of herring larval abundances, alongside sediment composition data. The IHLS conducts monitoring programmes where larvae numbers are recorded around the UK coastline and throughout the North Sea. Herring larvae are identified as being recently hatched by their size, with small herring larvae assumed to have been hatched recently and in close proximity to the area where eggs were laid (ICES, 2006; 2022b). The IHLS present herring larvae counts by size per m2, with larvae <10 mm long used as a cut off point for recently hatched larvae (ICES, 2022b).
81. High abundances of herring larvae are a good indication of recent spawning activity local to where these were sampled. These data were plotted for each year from 2007 to 2016 in Figure 4.9   Open ▸ to Figure 4.11   Open ▸ showing the changing spatial distribution of herring spawning relative to areas of historic spawning grounds as identified by Coull et al. (1998), in line with guidance from Boyle and New (2018).
82. Due to lack of IHLS survey data between 2017 and 2018, and a change in reporting strategy from IHLS, since 2019, more recent herring larvae data were not available for analysis. However, an ICES scientific report (ICES, 2021) noted that IHLS data for 2019 to 2020 in the Buchan area was in the same order of magnitude as previous years, therefore, it can be assumed that there are no significant changes from the results presented for 2007 to 2016 outside of normal annual variations.
83. These data show that the spawning ground adjacent to the north-west of the site boundary identified by Coull et al. (1998) has recorded persistently high levels of spawning activity with relatively little variation from 2007 to 2016. The spawning area identified to the south-west of the site boundary has had variable spawning levels from 2007 to 2016. It is worth noting that spatial variability of larval densities may be a result of the timing of data collection and/or variation in ocean and tidal current speeds and direction, which may account for some of the variability shown to the south-west of the site boundary. Both spawning areas identified through Coull et al. (1998) and the IHLS heat maps are supported by habitat suitability data from EMODnet, as shown in Figure 4.7   Open ▸ and Figure 4.8   Open ▸ by the large patches of favourable and marginal spawning habitat directly to the north and further south-west of the site boundary, which corresponds with spawning areas identified through particle size data and IHLS larval data.
84. Each year of data were also presented cumulatively over the ten year period between 2007 and 2016 ( Figure 4.12   Open ▸ ) to gain an understanding of where the most common spawning grounds were over the time period. As per Figure 4.12   Open ▸ , a persistent hotspot of high larval density is present towards the north-west of the site boundary. It should be noted that this is consistent with Coull et al. (1998), which demonstrates its continued relevance when assessing spawning grounds. These data align with what was reported in the post-consent fish monitoring strategy report for Seagreen Alpha and Bravo (now referred to as Seagreen 1 Offshore Wind Farm and Seagreen 1A Project) (Seagreen Wind Energy Ltd., 2019).
85. No high intensity spawning grounds identified by Coull et al. (1998) directly overlap with the site boundary. This is supported by the habitat suitability data from both site-specific sampling effort and broadscale EMODnet seabed substrates (following classifications in Reach et al., 2013), as shown in Figure 4.7   Open ▸ . The large patches of gravelly sand and >5% mud content reported provide unsuitable spawning habitat throughout much of the site boundary, with only four discrete areas of marginal/preferred spawning habitat identified out of 78 stations.

Figure 4.9: Herring Larval Density from IHLS Data Sets from 2007 to 2010

Figure 4.10: Herring Larval Density from IHLS Data Sets from 2011 to 2014

Figure 4.11: Herring Larval Density from IHLS Data Sets from 2015 and 2016

Figure 4.12: Herring Cumulative Larval Density from IHLS Data Sets from 2007 to 2016

4.5.        Sandeel

4.5. Sandeel

4.5.1.    Desktop Study

4.5.1. Desktop Study

86. There are five species of sandeel present in the North Sea which display differences in dwelling areas and abundances (e.g. intertidal zone versus deeper waters). While Raitt’s sandeel is the most abundant species supporting a large fishery in the North Sea, this section refers to sandeel species collectively, unless specified otherwise. Two sandeel species, Raitt’s sandeel and lesser sandeel are Scottish PMFs.
87. The wider Forth and Tay SMR has been known historically to support important sandeel populations. The highest density of this population is focussed on the Wee Bankie (approximately 57 km west of the site boundary), however sandeel do range across much of the wider North Sea. In the early 1990s, there was a substantial industrial sandeel fishery on the Wee Bankie, Marr Bank and Berwick Bank sandbanks. By 1993, landings from this area had peaked at over 100,000 tonnes (Greenstreet et al., 2010b).
88. In 2000, this industrial sandeel fishery was closed in response to concerns that the fishery was having a deleterious effect on sandeel stocks within the Forth and Tay SMR. The sandeel closure within this region (precautionary closure — Article 29a from Council Regulation No 850/88) had the effect of limiting sandeel fishing on most of the Forth and Tay SMR sandeel grounds. The fishery remains closed and sandeel abundance is monitored by Marine Scotland and ICES.
89. In 2000, the first year of the closure of the Forth and Tay SMR sandeel fishery, high levels of recruitment, combined with a lack of any significant fishing activity resulted in an immediate and substantial increase in the biomass of sandeel on the Wee Bankie sandbank (Greenstreet et al., 2010b). However, between 2001 and 2010, sandeel biomass steadily declined to levels that were similar to those observed when the sandeel fishery was active (Greenstreet et al., 2010b). This was thought to be due to the absence of sustained recruitment, meaning that predation and other causes of natural mortality still exceeded population growth (Greenstreet et al., 2010b). More recently sandeel stocks have recovered leading to an increase in sandeel fishing adjacent to the closed area, however, ICES (2022c) recently stated “The escapement strategy [by which sandeel stocks are managed] is not sustainable for short-lived species unless the strategy is combined with a ceiling on fishing mortality”.
90. Sandeel act as an umbrella species linking primary productivity to higher trophic levels and impacts on sandeel can cascade through the food chain. Sandeel feed exclusively on phytoplankton and zooplankton in the water column during the daytime and are an important prey items for many fish, seabirds, and marine mammals (Freeman et al., 2004; Engelhard et al., 2008). At night and during winter months, sandeel bury in the sediments, and high level site fidelity has been evidenced which puts them under potential threat of direct habitat loss (Jensen et al., 2011; Latto et al., 2013). This behaviour limits the habitat that sandeel can occupy to areas of very specific sediment particle sizes, where penetration into the sediment is possible. During the days of spring and summer months, sandeel tend to actively feed in schools within 10 km of their burying grounds (Wright et al., 2019). This is an adaptation to conserve energy and to avoid predation.
91. Sandeel remain buried in the seabed between September and February with occasional emergence between December and February to spawn a single batch of demersal eggs that are deposited on the seabed (van der Kooij et al., 2008). Larvae hatch between February and April and drift with currents within the plankton for ten weeks (Wright and Bailey, 1996; Régnier et al., 2017; Proctor et al., 1998; Wright et al., 2019). After metamorphosis, juveniles return to the demersal environment and look for suitable areas of sand to inhabit. There are indications that the survival of sandeel larvae is linked to the availability of copepod prey in the early spring, especially Calanus finmarchicus, and that climate generated shifts in the Calanus species composition can lead to a mismatch in timing between food availability and the early life history of lesser sandeel (Wright and Bailey, 1996; van Deurs et al., 2009).
92. Studies in the laboratory (Wright et al., 2000) and in the natural environment (Holland et al., 2005) have focussed on identifying the sediment characteristics that define the seabed habitat preferred by sandeel. Both approaches produced similar results, indicating that sandeel preferred sediments with a high percentage of medium to coarse grained sand (particle size 0.25 mm to 2 mm), and avoided sediment containing >4% silt (particle size <0.063 mm) and >20% fine sand (particle size 0.063 mm to 0.25 mm). As the percentage of fine sand, coarse silt, medium silt and fine silt (particles <0.25 mm in diameter) increased, sandeel increasingly avoided the habitat; this finding was also supported by Wright et al. (2000) as reported by Mazik et al. (2015). Conversely, as the percentage of coarse sand and medium sand (particles ranging from 0.25 mm to 2.0 mm) increased, sandeel showed an increased preference for this substrate.
93. Work by Greenstreet et al. (2010a) draws on the research by Holland et al. (2005), to define four sandeel sediment preference categories, using hydro-acoustic seabed surveys and nocturnal grab surveys. This work merged fine sand, three silt grades and two coarser sand grades, to define two particle size classes, silt and fine sand and coarse sand, and then examined the combined effect of these two size grades of sediment particles on the percentage of grab samples with sandeel present. Latto et al. (2013) used this research, along with that described above by Wright et al. (2000) to produce four sandeel sediment preference categories, which were defined as: Prime, Sub Prime, Suitable and Unsuitable (refer to Table 4.5   Open ▸ ). To align with the Folk (1954) categories presented within the EUSeaMap seabed substrates layer, shown in Figure 4.14   Open ▸ to Figure 4.16   Open ▸ , these categories have been presented as preferred (prime and sub-prime), marginal (suitable) and unsuitable substrate classifications, taken from Latto et al. (2013).
94. Further work has been completed by Langton et al. (2021) where a predicted distribution model for sandeel was developed, producing predicted density and probability of occurrence for sandeel around the British coastline. This modelling was undertaken based on the dependence of sandeel on particular habitat types, with the four main explanatory variables within the model being silt, depth, sand and slope, and was supported by sandeel fisheries data (e.g. data from Jensen et al., 2011). The results from Langton et al., (2021) within the fish and shellfish ecology study area were mapped, highlighting areas of importance for sandeel populations in the North Sea. Figure 4.13   Open ▸ presents the outputs of the modelling within the site boundary and shows that the whole site boundary has extremely low probability of sandeel presence, with areas where predicted density is high closer to the coasts or towards the Firth of Forth. These areas also correlate to previous studies which identified where marine mammals and birds are known to congregate and feed on sandeels (Langton et al., 2021).

Figure 4.13: Model Derived Predictions of Density and Probability of Presence of Sandeel within the Site Boundary (Derived from Langton et al. (2021))

4.5.2.    Site-Specific Surveys

4.5.2. Site-Specific Surveys

95. As outlined in section 3.3, site-specific survey data were collected and reviewed alongside desktop studies to assess the extent of suitable sandeel habitat within the site boundary. Grab sampling was undertaken (refer to section 3.3) and PSA completed on the sediment samples collected in 2022 within the site boundary which allowed classification of the sediment types according to Latto et al. (2013), as described in section 3.3. These classifications were originally developed for the marine aggregates industry, drawing on work from Greenstreet et al. (2010) and Holland et al. (2005), investigating spatial interactions between the aggregate application areas and sandeel habitat.
96. Figure 4.14   Open ▸ illustrates the results of this site-specific analysis with sandeel habitat sediment preference classifications of preferred, marginal and unsuitable habitat denoted in Table 4.5   Open ▸ . The distribution of the habitat suitability shows that the site boundary is characterised by preferred (sub-prime; seven stations) and marginal habitat (37 stations), accounting for 56% of the site boundary, and the remaining 44% (34 stations) of sediments sampled were considered unsuitable for sandeel habitation. Excesses of mud prevent sandeel maintaining their burrows as the burrows are more likely to collapse and can reduce the ability of sandeel to respire due to fine particulate clogging gill tissues. The north-west section is mostly characterised by marginal and preferred habitats, while the south-east is covered by patches of unsuitable and marginal habitat.

Table 4.5: Sandeel Habitat Sediment Classifications Derived from Latto et al. (2013)

97. Figure 4.14   Open ▸ illustrates the site-specific survey data alongside EMODnet seabed substrate data which can also be used to assign broadscale habitat suitability for sandeel. For the purposes of considering sandeel habitat suitability across the site boundary and surrounding areas, gravelly sand (between 30% and 5% gravel), slightly gravelly sand (between 5% and 1% gravel) and sand (under 1% gravel) in the EMODnet substrate data were classified as preferred habitat and sandy gravel (between 30% and 80% gravel) as marginal habitat. The substrates classified as preferred and marginal habitats all have a sand to mud ratio of nine to one or higher. Where no shading is present, the habitat in that area is considered unsuitable for sandeel.
98. Overall, results from the site-specific surveys do not align completely with the EMODnet seabed substrate data; this is generally to be expected when comparing broadscale data with site-specific or point source information. The EMODnet seabed substrate data is of lower resolution and accuracy than the results of the site-specific survey and is based upon a high degree of interpolation, and so should be interpreted with caution due to not accounting well for local scale variance. Regardless, this data is a useful tool to support a broadscale regional characterisation of the general surrounding substrate. While the site-specific survey data shows the north-west portion as preferred and marginal habitat and south-east as a mosaic of unsuitable and marginal habitat, EMODnet data suggests that the whole site boundary is covered by slightly gravelly sand which is a preferred habitat for sandeel. These data highlight a degree of fine-scale variation that is not possible to resolve when working with broadscale data alone, and highlights the patchy nature of sandeel habitat within the site boundary.
99. Further site-specific survey results from grab samples and epibenthic trawls have provided incidental data on the presence of sandeel within the site boundary; one grab sample and two beam trawl samples captured low numbers of sandeel (stations S058, BT001 and B002, see Figure 3.1   Open ▸ ) (see volume 3, appendix 8.1, annex A). These are shown in Figure 4.15   Open ▸ with records in grab samples shown as presence/absence and trawl data shown as abundances per 200 m trawled. The abundance data collected indicates higher abundances of sandeel in the north-west section of the site boundary which aligns with the composition of the sediments, which is less muddy and sandier compared to the south-east of the site boundary. However, it should be noted that neither grab sampling nor epifaunal trawling target sandeel specifically, therefore these results should be regarded as opportunistic. Conversely, whilst these opportunistic data may indicate higher abundances in specific areas (with regards to higher catchability due to higher density of burrows), it cannot be interpreted as low abundance or absence of sandeel where individuals were not recorded, due to the lack of specificity of sampling methods for sandeels. The site-specific survey data and desktop data indicate that sandeels are likely to be present across the site boundary, specifically in the north-west section, although almost half of the habitats recorded within the site boundary were assessed to be unsuitable or marginal grounds.

100. As in section 4.4.2 for herring, Figure 4.16   Open ▸ expands on the site-specific data presented in Figure 4.14   Open ▸ , as it includes results of PSA conducted on sediment samples obtained from the OneBenthic Portal in the fish and shellfish ecology study area outside of the site boundary (Cefas, 2019a). Of the 669 samples obtained from the OneBenthic Portal, 335 were assessed as unsuitable, 162 as marginal, and 172 as preferred spawning habitat.

Figure 4.14: Sandeel Habitat Preference Classification from EMODnet and Site-specific Survey Data

Figure 4.15: Sandeel Habitat Preference Classification with Site-specific Abundance Data

Figure 4.16: Sandeel Habitat Preference Classification from EMODnet and Spawning Habitat Classifications from the Site-Specific Survey Data and the OneBenthic Portal

4.6.        Elasmobranchs

4.6. Elasmobranchs

4.6.1.    Desktop Study

4.6.1. Desktop Study

101. Elasmobranchs are a group of cartilaginous fish encompassing sharks, rays and skates. Species reported to occur within the fish and shellfish ecology study area include basking shark, spotted ray, thornback ray, tope shark, small-spotted catshark, spurdog, common skate, thorny skate and cuckoo ray (Coull et al., 1998; Daan et al., 2005; Baxter et al., 2011; Ellis et al., 2012). There are no specific fisheries for these species, however most of these species have commercial value, but not locally to the site boundary. Some of these species have nursery grounds within the fish and shellfish ecology study area (Ellis et al., 2012) and were further discussed in section 4.3.
102. Basking shark may migrate throughout the fish and shellfish ecology study area and therefore have the potential to be encountered within the site boundary. Basking shark are large, filter feeding fish that are predominantly solitary, but may also occur in aggregations where there is dense zooplankton abundance (Speedie, 1999). Their unique feeding strategy dominates all aspects of their ecology and life history; the basking shark is an obligate ram filter feeder whereby the flow of water across gill rakers within the mouth is controlled by swimming speed (Sims, 1999; Sims, 2008).
103. Mating has not been observed in basking shark and most likely occurs in deep water with courtship-like behaviour as the precursor, particularly where individuals aggregate in food rich waters (Sims, 2008). Individuals are thought to pair and mate in early summer (Sims et al., 2000) and gestation has been estimated over a range of 12 to 36 months (Parker and Stott, 1965; Sims et al., 2008). As an ovoviviparous species, basking shark bear live young, hatched from eggs within the uterus of the female. Basking shark are a slow growing species with late maturation (at 12 to 20 years of age) and a relatively low fecundity (producing litters of around six pups; Sund, 1943). These characteristics suggest that basking shark would be vulnerable to environmental changes and the population would be slow to recover from any major losses. With a long history of exploitation, this species is listed as Vulnerable on the IUCN Red List globally (Fowler, 2009), and on the European Red List for cartilaginous fish as Endangered (IUCN, 2023). Basking shark are a Scottish PMF.
104. Basking shark migration routes cover large distances from north Africa to Scotland, using both the continental shelf and oceanic habitats in the upper 50 m to 200 m of the water column (Doherty et al., 2017). Distribution has been shown to be influenced by a range of environmental conditions (Austin et al., 2019). Surface sightings of basking sharks are typically reported where sea surface temperatures range between 15°C and 17.5°C (Skomal et al., 2004; Cotton et al., 2005) where thermal fronts are present (Sims and Quayle, 1998; Jeewoonarain et al., 2000) and where zooplankton is in its greatest abundance (Sims and Quayle, 1998; Sims, 1999). Basking shark have a north to south migration and may be expected to occur within and surrounding the site boundary during August to October and during the return migration in March to June (Doherty et al., 2017).
105. Twenty-eight basking sharks tagged off Scotland and the Isle of Man in summer months over four years showed an average migration distance of 1,057 km with movements starting in October (Doherty et al., 2017), however, none of the tagged basking sharks migrated to the east coast of Scotland. Due to the migratory behaviour of basking sharks and routes through Scottish waters, basking sharks have the potential to be present within the fish and shellfish ecology study area, however, the majority of basking shark sightings in UK waters are located on the west coast of Scotland (NBN Atlas, 2021).
106. Common skate are a Critically Endangered demersal elasmobranch (Ellis et al., 2021) found in the North-East Atlantic between 100 m and 1000 m on the continental shelf and slope and around seamounts (FishBase, 2022b). Their large size and life history traits (slow growth, late maturity and low fecundity) has caused them to be highly susceptible to overfishing (Griffiths et al., 2010), with significant decreases in population sizes and distribution range. Their widespread range historically extended from Iceland to north Africa, including the Mediterranean Sea, however, it has been reduced to the British Isles up to Iceland and its presence in the Mediterranean Sea has not been confirmed since records have been attributed to a separate distinct species: the flapper skate Dipturus intermedius (Mendez et al., 2022). Most recently, the majority of sightings around the British Isles were along the west coast of Scotland, the Irish Sea and the English Channel (NBN Atlas, 2021). This is supported by the two distinct populations highlighted in Griffiths et al. (2010), with one occurring in waters off the southern British Isles and around Rockall, and the other occurring in shelf waters along the west coast of Scotland. However, the nursery grounds located in the vicinity of the site boundary suggest that common skate could be present around the site boundary intermittently throughout spring and summer when common skate mate and lay egg capsules, respectively ( Figure 4.6   Open ▸ ; FishBase, 2022b).
107. Spotted ray are widely distributed across the eastern Atlantic from Morocco to the Shetlands Isles and Norway and were assessed as Least Concern according to the IUCN Red List (Stehmann and Burkel, 1984; Bauchot, 1987; Ellis et al., 2007). The populations in the North-East Atlantic show preferences for inshore waters and shallow continental shelf waters between 8 m and 283 m (Ellis et al., 2005) with higher abundances in shallow waters (up to 100 m). Spotted ray show generational segregation, with juveniles commonly occurring on sandy sediments closer inshore where they feed on small crustaceans and adults occurring further offshore on sand and coarse sand-gravel sediments predating on larger crustaceans and fish (Ellis et al., 2007). Individuals are known to bury themselves to avoid predation and to ambush prey. Sightings of spotted ray concentrate in the Irish Sea and in the southern North Sea (NBN Atlas, 2021). However, with low intensity nursery grounds overlapping the site boundary ( Figure 4.5   Open ▸ ) and records in the fish and shellfish ecology study area, spotted ray are likely to be present within and in the vicinity of the site boundary.
108. Sightings of spurdog have been recorded around the British Isles with most data from the Irish Sea (NBN Atlas, 2021). Spurdog are listed as Vulnerable on the IUCN Red List (Finucci et al., 2020) and they are a Scottish PMF with a known global distribution in boreal and temperate waters (Ebert et al., 2013). Spurdog dwell in a wide range of habitats both inshore and offshore waters from the surface down to 2,000 m (Cox and Francis, 1997). This species has been targeted and caught as bycatch in artisanal, industrial, and recreational fisheries as its distribution overlaps with intensive fishing activities (Finucci et al., 2020). The population decrease has been accentuated by their aggregation behaviour mostly between pregnant females (ICES, 2018). However, the large scale fishing pressure that targeted spurdog has largely diminished with retention bans implemented in European Union (EU) waters, and the stock was able to recover considerably. Nonetheless, incidental catches continue, and post-release mortality remains high (i.e. 39% for gillnet fisheries) (Rago and Sosebee, 2014; da Silva et al., 2015; Ellis et al., 2017; ICES, 2018). Spurdog are likely to be found within or in the vicinity of the site boundary, especially within the nursery grounds that overlap with the site boundary over the winter months when pups are born (Pawson and Ellis, 2005; Figure 4.5   Open ▸ ).
109. Tope shark is a species of shark with a global distribution in temperate waters (Compagno, 2005) but is listed as Critically Endangered (Walker et al., 2020). Tope shark is a benthopelagic species occurring on continental shelves and the upper half of continental slopes from shallow inshore to offshore waters up to 826 m (Walker et al., 2006; Wiegmann, 2016; Thorburn et al., 2019). Tope shark often gather in schools, partially segregating by size and sex and sometimes migrate between shallow waters at night to deep waters during the day (Walker et al., 2008). Tope shark is targeted globally for the shark flesh and fins and is caught as by-catch in various fisheries (i.e. industrial, small-scale, demersal, pelagic, gillnet, longline, trawl and hook-and-line) (ICES, 2019; Walker et al. 2020). In addition, tope shark’s low fecundity and late maturity has led to significant stock reductions (e.g. reduction of 76% of the North-East Atlantic subpopulation over 79 years). Implementation of management measures in Europe, including the mandatory release of line-caught tope shark in EU waters has helped maintain the North-East Atlantic population as stable in recent years but extensive movements remain within subpopulations. However, uncertainties remain for the correct identification of tope shark in trawl survey data which can be confused with smooth-hound Mustelus spp. (ICES, 2019). Tope shark have pupping and nursery grounds in shallow waters, protected bays and estuaries where juveniles may remain up to two years (Stevens and West, 1997, Walker, 1999, Walker et al., 2006, Bovcon et al, 2018, McMillan et al., 2018). Figure 4.6   Open ▸ shows the presence of nursery grounds for tope shark adjacent to the site boundary and tope shark are therefore likely present in the vicinity of the site boundary.
110. Among the other species of elasmobranchs likely to be present within the fish and shellfish ecology study area, angel shark Squatina squatina (Critically Endangered) (Morey et al., 2019) have been observed in the Firth of Forth but are likely to be vagrant, with the majority of sightings in the Irish Sea (NBN Atlas, 2021). The cuckoo ray is widely distributed throughout the North-East Atlantic and Mediterranean Sea. Cuckoo ray, a small bodied species of ray that typically occurs offshore on the continental shelf and slope at depths of 20 m to 500 m and the thorny skate, a Vulnerable demersal species that occurs on the continental shelves and slopes, have been observed in multiple locations in the northern North Sea (NBN Atlas, 2021). Small-spotted catshark and thornback ray are commonly recorded around the British Isles with lower occurrences in the northern North Sea (NBN Atlas, 2021) and porbeagle Lamna nasus, a large pelagic shark species occurring mostly offshore, have been sighted within the fish and shellfish ecology study area.

4.6.2.    Site-Specific Surveys

4.6.2. Site-Specific Surveys

111. No basking shark were recorded during the 24 months of aerial surveys undertaken for marine mammals and birds for the site boundary (refer to volume 3, appendix 11.1, annex D).
112. No elasmobranch species were recorded during the 2022 site-specific survey (grab/DDV or epibenthic beam trawls) within the site boundary (refer to volume 3, appendix 8.1, annex A). In the wider fish and shellfish study area, a single cuckoo ray was recorded during a 2011 epibenthic trawl for the Seagreen Alpha and Bravo project (now referred to as Seagreen 1 and Seagreen 1A) (Seagreen Wind Energy Ltd., 2012).

4.7.        Diadromous Fish

4.7. Diadromous Fish

113. Diadromous fish are species that migrate between freshwater and seawater. These are grouped into anadromous species, which live in the sea and migrate to freshwater to breed, and catadromous species which live in freshwater and migrate to sea to breed. On the east coast of Scotland, there is potential for diadromous fish to migrate through the fish and shellfish ecology study area to reach or to leave Scottish rivers. During migration, diadromous fish may migrate through the site boundary during certain times of the year (NBN Atlas, 2021).
114. The northern North Sea is home to diadromous fish species which move between the sea and freshwater at different stages of their life cycle. Atlantic salmon and sea trout are two commercially important diadromous fish species found in the North Sea. Sea lamprey Petromyzon marinus, river lamprey Lampetra fluviatilis, European eel Anguilla anguilla, allis shad Alosa alosa, twaite shad Allosa fallax and sparling Osmerus eperlanus are also known to occur in the region. Brook lamprey Lampetra planeri are also recorded in the fish and shellfish ecology study area, although as a purely freshwater species, this species migrates between downstream river habitat to upstream areas to spawn and are therefore not considered further in this report as they are unlikely to interact with the Array.
115. No site-specific surveys have been undertaken within the site boundary to support the impact assessment on diadromous fish species, nor were they undertaken at other offshore wind projects in the fish and shellfish ecology study area (Berwick Bank, Seagreen 1 and 1A, Neart na Gaoithe, or Inch Cape Offshore Wind Farms). Therefore, a precautionary approach has been taken when characterising the baseline for diadromous species. It has been assumed that the eight species mentioned in paragraph 114 may be present within the fish and shellfish ecology study area during key migration periods. Due to uncertainties in the migration routes and foraging areas and times for diadromous fish, it is also assumed that all relevant species have the potential to occur within the area year-round.
116. All species described in paragraph 113 are considered individually below with their likely presence within the site boundary defined and whether they are considered as IEFs for the fish and shellfish ecology assessment of effects. For example, some species (e.g. river lamprey) remain coastal during their time in the sea and are unlikely to migrate through the site boundary. Diadromous species presence in the fish and shellfish ecology study area and within the site boundary will vary throughout the year with presence likelihoods dependent on the key migration periods presented in Table 4.6   Open ▸ .

Table 4.6: Overview of Life Histories for Diadromous Fish Relevant to the Fish and Shellfish Ecology Study Area

4.7.1.    Atlantic Salmon

4.7.1. Atlantic Salmon

117. Atlantic salmon are an Annex II species under the Habitats Directives and are designated as a qualifying feature of Special Areas of Conservation (SACs) including European sites in Scotland, with some European sites located within the fish and shellfish ecology study area (such as the River Dee SAC and the River Tay SAC). Atlantic salmon are also defined as a PMF in Scotland for the marine life cycle and an Annex III species under the Bern Convention (for the freshwater life cycle). Atlantic salmon populations have seen a rapid decline across Scotland in the last 25 years (Youngson et al., 2002).
118. Atlantic salmon are of considerable cultural and conservation importance (Hindar et al., 2010). Atlantic salmon are subject to many pressures in Europe both in marine and freshwater environments, including pollution, the introduction of non-native salmon stocks, physical barriers to migration, exploitation from netting and angling, physical degradation of spawning and nursery habitat, and increased marine mortality (ICES, 2017; Cefas, 2019b).
119. Since 2016, as a result of the Salmon Conservation Regulations, Atlantic salmon caught in coastal waters have to be released. This was implemented to prevent the killing of Atlantic salmon in coastal waters and estuaries to protect stocks that were in poor conservation status.
120. Atlantic salmon are considered a Priority Species under the UK Post-2010 Biodiversity Framework. The species is known to be a relatively large bodied fish that can be encountered in clean and healthy rivers throughout the UK. Like other salmonid species, the Atlantic salmon spends most of its life at sea, returning to spawn in the same stretch of river or stream in which they was born (natal river).
121. Adult Atlantic salmon spawn in Scottish east coast rivers and after the ova mature to fry and then parr, the smolts migrate to the sea. After one to three years at sea, adults migrate, usually, to their native river. Various cues are involved during their return migration; in earlier phases, sun position and Earth’s magnetic field seem to play a role in oceanic orientation (Hansen and Quinn, 1998). Tidal phase and time of day have also been suggested as important factors for their upstream migration (Smith and Smith, 1997). Migration upstream of estuaries have also been observed to be nocturnal, occurring during ebb tides (Smith and Smith, 1997). In the final phase of the upstream migration, olfactory cues direct Atlantic salmon up the river (Hasler and Scholz, 1983). For smolts migrating downstream, migratory activity has been identified to be associated with night time while daytime was utilised more for prey detection and predator avoidance (Hedger et al., 2008). East coast Scotland post-smolts, once in the North Sea, are transported by water currents towards northern Norway and then into the Norwegian Sea (Holst et al, 2000; Jonsson et al., 1993). Further evidence from Scottish Atlantic salmon (i.e. from Aberdeenshire Dee, Tay and North Esk rivers) recaptured in Greenland and Faroe Islands waters showed that smolts emigrated west to feed and grow (Malcolm et al., 2010).
122. This is further supported by recent evidence from the Moray Firth (Newton et al., 2017; Newton et al., 2019; Gardiner et al., 2018a) which suggests that smolts migrating from their rivers in the Moray Firth head directly across the North Sea relatively rapidly. It is thought that this route, rather than moving in a coastal direction upon leaving their natal rivers, allows them to take advantage of east flowing currents which cross the North Sea. This fast progress away from the coast limits exposure to predators occurring close to the coast; it also reduces the potential for interaction with marine renewables developments (including offshore wind). Similar evidence of a rapid easterly migration out into the North Sea has also been shown for the River Dee in Aberdeenshire (Gardiner et al., 2018b). Therefore, it could be assumed that smolts from other east coast rivers (e.g. Tay, Forth and South Esk) would move in a similar fashion.
123. Malcolm et al. (2015) used metadata to assess the timing of smolt emigration across Scotland. This suggested that most fish leave rivers between mid-April and the end of May. These results do not include the period spent by smolts in the coastal environment after leaving their native rivers. There was also evidence that smolt emigration is becoming earlier (by around 1.5 days per decade over a period of around 50 years).
124. Migration of Atlantic salmon smolts through the Cromarty Firth and into the Moray Firth was tracked in a study undertaken for Beatrice Offshore Windfarm Ltd. by Glasgow University (BOWL, 2017). The study results indicated an eastwards migration of the tagged fish along the southern coast of the Moray Firth. Results also showed the majority of fish to remain predominantly within the upper 1 m of the water column during migration. Mortality of smolts was considered mainly attributable to predation and there was a strong relationship between group survival, early migration and group size.
125. Between 2018 to 2021, a tagging study was conducted on juvenile Atlantic salmon and sea trout migrating from the River Dee and River Don, which are located in Aberdeenshire (in the north of the fish and shellfish ecology study area) (River Dee Trust and MSS, 2023). Atlantic salmon were found to travel at an average speed of 0.45 m/s from the river mouths to around 4 km offshore, before dropping to 0.24 m/s between 4 to 20 km offshore (River Dee Trust and MSS, 2023). Individuals mostly swam within the top 3 m of the water column and swam in an easterly direction in the first 4 km, before following a south-easterly trajectory. This pattern was consistent over the three years of the study, suggesting that this is a regular migratory route and that Atlantic salmon must make a northerly course adjustment at some point in their migration to reach higher latitude feeding grounds in the Norwegian Sea (River Dee Trust and MSS, 2023). The authors concluded that this easterly and south-easterly migratory trajectory suggests that Atlantic salmon could be present in offshore areas of the North Sea (River Dee Trust and MSS, 2023).
126. The wild Atlantic salmon total catch from rod fishing reported 42,204 individuals in 2022, the fourth lowest record since the start of the statistics on salmon fisheries in Scotland by Marine Scotland in 1952 (Scottish Government, 2023). This is an increase from the 35,693 recorded in 2021 (Marine Scotland, 2022a), but still supports the population declines of Atlantic salmon in Scotland. Most of the catch data (97%) in 2022 are salmon caught by rod fisheries with 95% of the catches released. Other fishing methods (e.g. net and coble or fixed engine fisheries) accounted for 2% or less (Scottish Government, 2023). For retained catch data, rods accounted for around 74% while net and coble fisheries accounted for 26%. Historically, between 1952 and 2022, total rod catches of Atlantic salmon increased until its peak in 2010 and sharply declined since then to the current historic low.
127. Using rod catch data from relevant Scottish east coast rivers (Marine Scotland, 2022a), trends in Atlantic salmon populations in the fish and shellfish ecology study area can be highlighted. Data from 2021 on the number of fish caught in each of the following rivers have been collated in Figure 4.17   Open ▸ for the Tweed, Teith, Tay, South Esk, and Dee. It should be noted that data for 2022 were not available at the time of writing. The five year average between 2017 and 2021 of Atlantic salmon caught by rods has also been provided. Figure 4.17   Open ▸ demonstrates that Atlantic salmon migrate to and from east coast Scottish rivers. Therefore, migrating smolts or returning adults are likely to pass through the site boundary during migration periods. This is consistent with assumptions made for Seagreen 1 and 1A and Berwick Bank Offshore Wind Farms (Seagreen Wind Energy Ltd., 2012, SSER, 2022).
128. During their oceanic phase, Atlantic salmon are thought to use chemoreceptor in coastal waters to locate their natal river and electromagnetic fields (EMFs) during offshore migrations (Gill and Bartlett, 2010). However, Atlantic salmon being a pelagic species, the effects would be mostly perceived in shallower waters away from the location of the site boundary (Snyder et al., 2019).
129. Atlantic salmon and sea trout are host species for the freshwater pearl mussel Margaritifera margaritifera during their larval stage from late summer before they settle on the riverbed. Freshwater pearl mussel are strict freshwater species and have seen population declines. Amongst the factors that threaten their populations is the decline in salmonid stocks. Therefore, the impacts to Atlantic salmon and sea trout can directly affect the populations of freshwater pearl mussel.

Figure 4.17 Marine Scotland Catch Data for Rod Caught Atlantic Salmon (2017 to 2021)

4.7.2.    Sea Trout

4.7.2. Sea Trout

130. Sea trout are known to be found in rivers, streams and lakes, often preferring cold and well oxygenated waters. Sea trout spawn in rivers and streams that have swift currents, which are usually characterised by the downward movement of water into gravel, favouring large streams and mountainous areas that have adequate cover resulting from submerged rocks, undercut banks, and overhanging vegetation (Fishbase, 2021a). While there is limited information regarding sea trout migration patterns, the information available suggests preferences are primarily limited to inshore and local waters within the marine environment (Malcolm et al., 2010). Sea trout are listed as a Scottish PMF during the marine part of their life cycle.
131. The wild sea trout total catch from rod fishing reported 14,509 individuals in 2022 the fourth lowest record since the start of the statistics on sea trout fisheries in Scotland by Marine Scotland in 1952 (Scottish Government, 2023). This is an 11% increase upon the 12,636 individuals recorded in 2021 (Marine Scotland, 2022b). Most of the catch data (91%) in 2022 are sea trout caught by rod fisheries with 87% of the catches released. Other fishing methods (e.g. net and coble or fixed engine fisheries) accounted for 5% or less per method. For retained catch data, rods accounted for around 64% while net and coble fisheries accounted for 13% and 23% respectively. Historically, between 1952 and 2022, total rod catches of sea trout showed a general decreasing trend (Scottish Government, 2023).
132. Using rod catch data from relevant Scottish east coast rivers (Marine Scotland, 2022b), trends in sea trout populations within the fish and shellfish ecology study area can be highlighted. Data from 2020 on the number of fish caught in each of the following rivers have been collated in Figure 4.18   Open ▸ : Tweed, Tay, South Esk, and Dee. It should be noted that these are the most recent available data at the time of writing. The five year average between 2016 and 2020 of sea trout caught by rods has also been provided. Figure 4.18   Open ▸ demonstrates that sea trout migrate to and from east coast Scottish rivers. Therefore, migrating smolts or returning adults are likely to pass through the site boundary during migration periods. This is consistent with assumptions made in Seagreen 1 and 1A and Berwick Bank Offshore Wind Farms (Seagreen Wind Energy Ltd., 2012: SSER, 2022).
133. However, as described in paragraph 125, a recent tracking study provides insight into migratory routes for juvenile sea trout from the River Dee and the River Don (River Dee Trust and MSS, 2023). In this study, between 2018 and 2021, sea trout remained in the nearshore environment to a greater extent than Atlantic salmon and exhibited a range of different migration strategies. These included freshwater migration only (potamodromous; 18% of individuals), from freshwater to estuaries (semi-anadromous; 37%), and migration from freshwater to marine environments (anadromous; 45%) (River Dee Trust and MSS, 2023). Anadromous sea trout tended to stay between 4 km from the shore, and within the top 3 m of the water column. The authors suggested that sea trout from the River Dee and River Don are less likely to be present offshore than Atlantic salmon (River Dee Trust and MSS, 2023).

Figure 4.18: Marine Scotland Catch Data for Rod Caught Sea Trout (2016 to 2020)

4.7.3.    European Eel

4.7.3. European Eel

134. European eels are classified as Critically Endangered (IUCN, 2023) and are a Scottish PMF during the marine part of their life cycle. European eel dwell in a range of benthic habitats from streams to shores, rivers, lakes, and ultimately migrate to the Sargasso Sea to spawn. Eel larvae are brought to European waters by the Gulf Stream and transform into glass eel, followed by elvers which migrate up estuaries around the Scottish coast, colonising rivers and lakes. Sexually mature eels leave the river and migrate to sea, covering great distances during their spawning migration (5,000 km to 6,000 km) (Fishbase 2021b). European eel may migrate in the vicinity of or through the site boundary and therefore, given their critically endangered status, will be considered as an IEF.

4.7.4.    Sea Lamprey

4.7.4. Sea Lamprey

135. Sea lamprey are anguilliform (or eel-like) jawless fish found primarily in estuaries and easily accessible rivers, and are parasitic on a number of fish species and other marine fauna. Sea lamprey is the largest of the lamprey species found in the UK. Sea lamprey are anadromous (JNCC, 2021a) and spend most of their adult life at sea. Like other lamprey species, sea lamprey requires clean gravel for spawning, preferably in warm waters, and marginal silt or sand for the burrowing of juveniles (ammocoetes). Spawning of sea lamprey coincides with the warmer spring temperatures in Scottish rivers (refer to Table 4.6   Open ▸ ) (JNCC, 2021a).
136. Sea lamprey’s natural range has declined in the UK due to river pollution and barriers to migration (such as dams and weirs) but they remain widespread in UK rivers up to Scotland with a northern limit at the Great Glen (JNCC, 2021a). Sea lamprey are Annex II species on the Habitats Directive and are the primary reason or qualifying features for some designated sites on the east coast of Scotland (refer to section 4.7.8). They are also listed as a Scottish PMF during the marine part of their life cycle. However, there is limited information on the distribution and behaviour of sea lamprey in marine waters (Hume, 2017). While it is possible that migration routes may overlap with the site boundary, considering the distance to the nearest SAC (i.e. 128.58 km to Tweed Estuary SAC), the presence of sea lamprey within or in the vicinity of the site boundary is unlikely and sea lamprey are not considered as IEFs.

4.7.5.    River Lamprey

4.7.5. River Lamprey

137. The river lamprey has a similar body shape to the sea lamprey and inhabit coastal waters, estuaries, and accessible rivers. While some populations reside permanently in freshwater, the species is normally anadromous, and pollution or obstacles can hinder their migration (JNCC, 2021b). River lamprey live on hard bottoms or as parasites attached to larger fish such as cod and herring with spawning taking place in pre-excavated pits in riverbeds. River lamprey are widespread in UK rivers up to Scotland with a northern limit at the Great Glen and the populations in the UK are considered of conservation importance at European level (Hume, 2017). Like sea lamprey, river lamprey are also listed as Scottish PMFs during the marine part of their life cycle. Due to their preference for estuarine and nearshore coastal waters, it is unlikely that river lamprey will be found within the site boundary and are therefore not considered as IEFs.

4.7.6.    Allis and Twaite Shad

4.7.6. Allis and Twaite Shad

138. The two shad species are very similar in appearance and are hard to distinguish. They both belong to the herring family (Clupeidae) and the only reliable way of differentiating the two species, apart from allis shad being usually bigger, is the number of gill-rakers (JNCC, 2021c).
139. The habitat requirements of twaite shad are not decisively understood, however they are known to return to rivers from the sea to spawn in spring ( Table 4.6   Open ▸ ). On the River Usk and the River Wye, twaite shad are known to spawn at night shallow areas near deeper pools, in which the fish congregate. The eggs are released into the water column, sinking into the interstices between coarse gravel/cobble substrates (JNCC, 2021c). Recruitment yield is usually greater during warm years. The majority of adults (75%) generally die after spawning, and pollution, overfishing and migration obstacles have caused population declines (JNCC, 2021c). No spawning stocks of twaite shad are found in Scotland.
140. The allis shad also has poorly understood habitat requirements in freshwater. It grows in coastal waters and estuaries, spending most of its adult phase in the marine environment, but migrates into rivers to spawn, swimming up to 800 km upstream in continental Europe. Adults spawn at night with the eggs released into the current where they settle among gaps in gravelly substrates. Shallow gravelly areas adjacent to deep pools are thought to represent optimal spawning habitat (JNCC, 2021d). The majority of the adults die after spawning and migration obstacles are a major cause of population declines as well as pollution and overfishing. There is no clear spawning site in Scotland but there is probably a spawning population in the Solway Firth (Maitland and Lyle, 2001).
141. Both species have limited research surrounding their freshwater life cycle phases which has subsequently resulted in scarce understanding of their spatial ecology during the species marine life-phases (Davies et al., 2020). These species are considered unlikely to be found in significant numbers within the vicinity of the site boundary, however they are considered as IEFs to ensure a precautionary approach.

4.7.7.    Sparling (European Smelt)

4.7.7. Sparling (European Smelt)

142. Sparling or European smelt are known to inhabit estuaries and large lakes, spending much of their life in the estuarine zone, with short incursions into the littoral zone. Sparling have been evidenced to enter rivers to spawn on both sandy and gravelly substrates, predominantly in fast flowing waters of lake tributaries or shallow shores of lakes and rivers (Fishbase, 2021c). Sparling are listed as Scottish PMFs during the marine phase of their life cycle. Due to their preference of inhabiting estuarine waters upon entering the marine environment, it is unlikely that sparling will be found within and in the vicinity of the site boundary and are therefore not considered as IEFs.

4.7.8.    Freshwater Pearl Mussel

4.7.8. Freshwater Pearl Mussel

143. The freshwater pearl mussel is an endangered species of freshwater mussel and is included with diadromous fish as per standard EIA approach due to its reliance on salmonids during the first year. Freshwater pearl mussels are similar in shape to common marine mussels but grow much larger and live far longer. They can grow as large as 20 cm and live for more than 100 years, making them one of the longest- lived invertebrates (Skinner et al., 2003). These mussels live on the beds of clean, fast flowing rivers, where they can be buried partly or wholly in coarse sand or fine gravel. Mussels have a complex life cycle, living on the gills of young Atlantic salmon or sea trout, for their first year, without causing harm to the fish (Skinner et al., 2003). Freshwater pearl mussel is fully protected under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended) and is also listed on Annexes II and V of the Habitats Directive and Appendix III of the Bern Convention. The conservation status of the species is reflected in its listing as Endangered on the IUCN Invertebrate Red List. While there is no potential for direct impacts on this species from the site boundary (as this is an entirely freshwater species), indirect impacts may occur due to effects on their host species (i.e. Atlantic salmon and sea trout) during their marine phase.

4.8.        Shellfish

4.8. Shellfish

144. Shellfish is a colloquial and fisheries term that generally refers to exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms but also includes cephalopods. Note that species such as horse mussel Modiolus modiolus and ocean quahog Arctica islandica, along with other non-commercial species of shellfish and habitats created by shellfish species (such as mussel beds) are considered benthic species and are characterised within volume 3, appendix 8.1. Shellfish communities contribute to the biodiversity of the benthic ecosystem and are an important link in the food chain, both as predators and prey. The population structure of shellfish stocks around the UK is not fully understood, with assessments largely based on previous fishing and landings data and sometimes surveys (e.g. Nephrops) (Mesquita et al., 2016). Only a limited number of species have a stock assessment undertaken regularly (i.e. edible crab, velvet swimming crab, European lobster, Nephrops and scallops) (Marine Scotland, 2013), therefore, commercial landings data in the area provides an overview of species likely to be present.
145. As described previously, there are a number of commercially important shellfish species within the fish and shellfish ecology study area. Commercial landing data can be used as a proxy for identifying species present in the fish and shellfish ecology study area and in the vicinity of the site boundary, which include Nephrops, edible crab, European lobster, velvet swimming crab, king scallop, whelks and squid, as described in volume 3, appendix 12.1. There are consistently high landings of Nephrops, and medium to low landings of European lobster, edible crab, velvet swimming crab, king scallop, whelks, razor clam Solenidae spp., squid, and octopuses (between 2009 and 2015: Mesquita et al., 2016, 2017, and 2020 to 2021: Marine Scotland, 2021; 2022c). Occasionally caught species include green crab, northern stone crab Lithodes maja, spiny lobster Palinurus elephas, common prawn Palaemon serratus and queen scallop (Marine Scotland, 2021).
146. Site-specific DDV and epibenthic beam trawl surveys for Berwick Bank Offshore Wind Farm recorded Nephrops, edible crab and king scallop, albeit in low abundances (SSER, 2022). Shellfish found in high abundances in epibenthic trawls included brown shrimp and other shrimp species (Pandalidae spp.), however, these are not a key target of commercial fisheries within the area.
147. Site-specific surveys for Seagreen Alpha and Seagreen Bravo (now referred to as Seagreen 1 and 1A) (Seagreen Wind Energy Ltd., 2012) also reported edible crab, velvet swimming crab and king scallop in epibenthic beam trawls.

4.8.1.    King and Queen Scallop

4.8.1. King and Queen Scallop

148. Scallops show a preference for areas of clean firm sand, fine or sandy gravel and may occasionally be found on muddy sand. Distribution of these species is invariably patchy (Carter, 2009; Marshal and Wilson, 2009) but the areas with greatest abundance tend to be areas of little mud and with good current strength.
149. King scallop achieve reproductive maturity between three to five years, live upwards of 15 years and are evidenced to be most abundant in depths of 20 m to 70 m (Howarth and Stewart, 2014; Salomonsen et al., 2015; Cappell et al., 2018). Queen scallop are usually found on sand or gravel to depths up to 100 m but also occur amongst horse mussel beds (MarLIN, 2023).
150. Key physical differences between king and queen scallop are illustrated as queen scallop possessing two distinctive curved shells, while the king scallop’s upper shell is predominantly flat and are typically larger overall. Queen scallop stocks are known to be more highly mobile than king scallops, especially within the summer months when queen scallops are more actively swimming.
151. In Scottish waters, scallops spawn for the first time in the autumn of their second year, and subsequently spawn each year in the spring or autumn. After settlement, scallops grow until their first winter, during which growth usually ceases. Thereafter, growth resumes each spring and ceases each winter, causing a distinct ring to be formed on the external surface of the shell (Scottish Government, 2012).
152. King scallop are targeted commercially through dredge fisheries in the fish and shellfish ecology study area, although not within the site boundary. Within the fish and shellfish ecology study area, the majority of the activity, albeit moderate, is concentrated within ICES rectangles outside of the site boundary (refer to volume 3, appendix 12.1). Queen scallop were recorded during the site-specific benthic surveys across the site boundary (refer to volume 3, appendix 8.1, annex A).

4.8.2.    European Lobster

4.8.2. European Lobster

153. European lobster can be found from Scandinavia to north Africa and throughout the British coasts on rocky substrata, down to depths of 60 m. After moulting in summer, European lobster mate and larvae will remain planktonic for up to four weeks before settling onto the seabed in solitary shelters (Cefas, 2020a). They are usually relatively sedentary with some inshore to offshore migration recorded in some locations (Cefas, 2020a). European lobster are actively fished, mostly in inshore waters, with low landings recorded for the ICES rectangles that overlap with the site boundary (41E9, 42E9, 42F0) (refer to volume 3, appendix 12.1).

4.8.3.    Edible Crab

4.8.3. Edible Crab

154. Edible crab are a relatively long-lived species that is found on all coasts around Britain from the intertidal zone down to depths of 100 m. They live on rocky, gravelly substrate within which they bury into. Following spawning there is a larval dispersal phase of around 30 to 50 days. Stock boundaries are not well defined and edible crabs move over large areas. Females have been found to travel long distances from spawning areas (Cefas, 2020b). For females carrying eggs, there is an inactive brooding period in winter. The eggs hatch in spring and summer and larvae remain in the plankton for about five weeks. Edible crab mating activity peaks in summer and spawning follows later in autumn or during winter (Cefas, 2020b). Like European lobster, there are low landings of edible crab within the ICES rectangles that overlap with the site boundary (41E9, 42E9, 42F0) (refer to volume 3, appendix 12.1).

4.8.4.    Velvet Swimming Crab

4.8.4. Velvet Swimming Crab

155. Velvet swimming crab can be found around the coast of Britain and are found on stony/rocky substrate intertidally and down to depths of 100 m (Howson and Picton, 1997). Velvet swimming crab are targeted by commercial fisheries with higher commercial values available in continental Europe and they are often caught alongside European lobster and edible crab (refer to volume 3, appendix 12.1).
156. Velvet swimming crab were also recorded within the Berwick Bank Offshore Wind Farm (SSER, 2022) and therefore can be assumed to be present in the vicinity of the site boundary.

4.8.5.    Squid

4.8.5. Squid

157. Loliginid squid species are reported to be found over sand and muddy bottoms (Wilson, 2006) and are mostly demersal in nature, therefore are often captured as bycatch in demersal fisheries (Bellido et al., 2001). Ommastrephid squid species however are pelagic and are therefore often under-represented in trawl survey data and fisheries statistics. Research on squid indicates that they are probably batch spawners, however, this can vary depending on species, with some species utilising hard substrate for spawning purposes (Guerra and Rocha, 1994). Squid are typically short-lived species, with some loliginids recorded to live between 12 and 16 months (Guerra and Rocha, 1994). Many squids are semelparous, meaning that they will only spawn once and die shortly after (Hendrickson and Hart, 2006). In Scottish waters, squid exhibit a distinct seasonal migration pattern, travelling up to 500 km from the west coast of Scotland to the east coast in the winter months (Hastie et al., 2009). Squid are targeted by commercial fisheries, although main areas of fishing activity are within coastal waters and do not directly overlap the site boundary (refer to volume 3, appendix 12.1).

4.8.6.    Nephrops

4.8.6. Nephrops

                        Desktop study

158. Nephrops, known variously as the Norway lobster, Dublin Bay prawn, langoustine or scampi, are slim, orange pink lobsters which grows up to 25 cm long, and are considered to be the most commercially important crustacean in Europe (Bell et al., 2006). Nephrops are exploited throughout their geographic range, from Icelandic waters to the Mediterranean Sea and the Moroccan coast.
159. Nephrops are opportunistic predators, primarily feeding on crustaceans, molluscs and polychaete worms. They inhabit muddy seabed sediments and show a strong preference for sediments with more than 40% silt and clay (Bell et al., 2006). They build and spend significant amounts of time in semi-permanent burrows which vary in structure and size but typically range from 20 cm to 30 cm in depth (Dybern and Hoisaeter, 1965). Due to strong habitat preferences, distribution patterns of Nephrops are determined by the presence of suitable habitats, with higher abundances found on more favourable substrates.
160. Female Nephrops usually mature at three years of age and reproduce each year thereafter. After mating in early summer, Nephrops spawn in September and carry eggs under their tails (described as being 'berried') until they hatch in April or May. The larvae develop in the plankton before settling to the seabed six to eight weeks later (Coull et al., 1998). Within the fish and shellfish ecology study area, unspecified intensity nursery and spawning grounds for Nephrops are present within the south-west (56.57 km from the site boundary) and northern sections (45.94 km from the site boundary) but neither grounds coincide with the site boundary itself ( Figure 4.6   Open ▸ ).

                        Site-specific surveys

161. As discussed in paragraph 159, Nephrops display a strong preference for muddy sediments (silt and clay), therefore with the majority of the site boundary characterised as sandy substrata, this area is considered unsuitable for Nephrops. No observations were made of Nephrops during the site-specific epibenthic trawl survey or combined grab and DDV sampling conducted within the site boundary. The biotope that Nephrops are typically associated with (sea pen and burrowing megafauna communities) (JNCC, 2021e) was not found to be present across the site boundary. As such, the site boundary is unlikely to be an important area for Nephrops.

4.8.7.    Whelk

4.8.7. Whelk

162. Common whelk are an opportunistic carnivorous species, distributed throughout the north Atlantic Ocean. This species will typically inhabit subtidal areas, although they have been recorded on all types of seabed substratum including gravel, sand, mud and rock (Haig et al., 2015).
163. They are commercially exploited in UK waters, with much of the catch exported to East Asia (Eastern Inshore Fisheries and Conservation Authority (IFCA), 2020). They are vulnerable to exploitation as they are slow-growing and slow to reach sexual maturity (Eastern IFCA, 2020). Furthermore, recent studies have demonstrated that whelk show local differences in growth rates, suggesting that they are caught and landed before reaching sexual maturity in some areas (Haig et al., 2015; McIntyre et al., 2015).

4.9.        Designated Sites

4.9. Designated Sites

164. With the exception of sea trout, European eel and sparling, all the migratory fish discussed in section 4.7 are listed as Annex II qualifying features under the Habitats Directive (Council Directive 92/43/EEC) which provides them with protection and ensures their populations and habitats are maintained or restored through the designation of a SAC. Only Atlantic salmon and both lamprey species are qualifying features of SACs within the regional fish and shellfish ecology study area ( Table 4.7   Open ▸ ). Other non-migratory fish and shellfish species that are qualifying features of designated sites have been considered for the fish and shellfish assessment where applicable to this topic ( Table 4.7   Open ▸ , Figure 4.19   Open ▸ ). Further details on the assessments against the conversation objectives of each European site (i.e. SAC) and each qualifying feature is presented in the Report to Inform the Appropriate Assessment (RIAA).

Table 4.7: Designated Sites with Fish and Shellfish Qualifying Features within the Fish and Shellfish Ecology Study Area

Figure 4.19: Designated Sites with Fish as Qualifying Features

5.             Summary

5. Summary

165. The following sections provide a summary of the fish and shellfish baseline characterisation and detail the resultant IEFs to be considered in the Array EIA Report.

5.1.        Baseline

5.1. Baseline

166. The fish assemblage within the site boundary is typical of the northern North Sea. This is confirmed through site-specific survey and baseline data available from other developments in vicinity of the site boundary, with a mix of demersal and pelagic species. There are known overlapping spawning and nursery grounds for 16 species with the site boundary, including spawning grounds for cod and sandeel. Herring spawning grounds were further investigated and the results showed that there is some spawning activity which occurs adjacent to the site boundary with the majority of herring spawning occurring directly to the north with some further activity to the south of the site boundary. The site-specific PSA data supports very low proportions of the site boundary being suitable for herring spawning activity with only four sites described as either preferred or marginal habitat out of 78 sampled for PSA. Habitat suitability for sandeel was also assessed, with more than half of the site boundary having marginal and, in some areas, preferred habitat for sandeel habitation and spawning.
167. Eight species of diadromous fish were identified as having the potential to be present within fish and shellfish ecology study area, of which Atlantic salmon, sea trout, European eel and allis and twaite shad were deemed to have the potential to occur within the site boundary. Six SACs and one SSSI designated for diadromous fish species (and freshwater pearl mussel) are present (or with the potential to be present, however remote) within the fish and shellfish ecology study area. There was also one Nature Conservation MPA designated for sandeel present within the fish and shellfish ecology study area.
168. Shellfish in the fish and shellfish ecology study area and within the site boundary include Nephrops, king and queen scallop, European lobster, edible crab, velvet swimming crab and squid, which are targeted by commercial fisheries in the locality. Nephrops habitat was assessed using combined outputs from underwater imagery, grab sampling and epifaunal trawling alongside desktop data, which concluded that no favourable habitat was present within the site boundary.

5.2.        Important Ecological Features

5.2. Important Ecological Features

169. IEFs are habitats, species, ecosystems and their functions/processes that are considered to be important and potentially impacted by the Array. Guidance from the CIEEM was used to assess IEFs within the area (CIEEM, 2022). IEFs can be attributed to individual species (such as plaice) or species groups (for example other flatfish species). Each IEF is assigned a value or importance rating which are based on commercial, ecological and conservation importance, including PMF and features of SACs. PMFs are those species most threatened, in greatest decline, or where Scotland hold a significant proportion of the world’s total population in some cases. Therefore, they are considered to be marine nature conservation priorities. Table 5.1   Open ▸ details the criteria used for determining IEFs and Table 5.2   Open ▸ applies the defining criteria to specific species, providing justifications for importance rankings.

Table 5.1: Defining Criteria for IEFs

Table 5.2: IEF Species and Representative Groups to be taken forward to the Assessment

*Based on likelihood of presence in study area

6.             References

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[*] Ammodytes marinus described herein as Raitt’s sandeel.

[1] Adapted from Coull et al. (1998) and Ellis et al. (2012)

[2] Adapted from Coull et al. (1998) and Ellis et al. (2012)