2. Study Area

  1. Marine mammals are spatially and temporally variable, therefore for the purposes of the marine mammal baseline characterisation, two study areas have been defined ( Figure 2.1   Open ▸ ):
  • Proposed Development marine mammal study area: this is an area encompassing the Proposed Development array area and the Proposed Development export cable corridor plus a (approximate) 16 km buffer, including the area to the north and south of the proposed landfall location. This combined area was surveyed by the 2019 to 2021 aerial surveys ( Figure 4.3   Open ▸ Figure 2.1   Open ▸ ). It should be noted that the Proposed Development marine mammal study area has been defined based on the Proposed Development array boundaries at the time of the Scoping phase (SSER, 2021a). The Proposed Development array area has been subsequently amended; however, as the refinements resulted in a reduction of the Proposed Development array area, the Proposed Development marine mammal study area is considered to remain representative and conservative for the current assessment. Given that the Proposed Development marine mammal study area has not been realigned to the current Proposed Development boundary, the buffer encompassing the Proposed Development array area may be equal to or greater than 16 km in some locations, including to the north-west, south-west and south-east of the Proposed Development array area.
  • Regional marine mammal study area: marine mammals are highly mobile and may range over large distances and therefore, to provide a wider context, the desktop review considers the marine mammal ecology, distribution and density/abundance within the wider northern North Sea. The boundaries of the northern North Sea are closely aligned with those of Marine Natural Areas (Wildlife Trusts, 2021). The regional marine mammal study area has informed the screening of internationally designated sites and is also the area within which cumulative projects were defined.
    1. In accordance with advice received during consultation where population level effects were considered for a given species-impact pathway these were informed by species Management Units (MUs). The Inter-Agency Marine Mammal Working Group (IAMMWG, 2015) provided advice on cetacean MUs and the Special Committee on Seals (SCOS) provided advice on seal MUs (SCOS, 2021). Whilst these MUs provided reference populations for each species it was agreed during consultation that, where MUs for a given species extended over a very large scale (e.g. minke whale Balaenoptera acutorostrata and white-beaked dolphin Lagenorhynchus albirostris MUs extend over the Celtic and Greater North Sea (CGNS)), the assessment will also consider effects over a smaller scale; within Small Cetacean Abundance in the North Sea (SCANS) III Block R (noting that this is not an ecologically defined area).

Figure 2.1:
Marine Mammal Study Areas

Figure 2.1:  Marine Mammal Study Areas

3. Consultation

  1. A summary of the key issues raised during consultation activities undertaken to date specific to marine mammals is presented in Table 3.1   Open ▸ . Consultation was undertaken with key stakeholders to discuss baseline data sources and any further information sources of relevance.


Table 3.1:
Summary of Key Consultation Undertaken of Relevance to Marine Mammal Baseline Characterisation

Table 3.1: Summary of Key Consultation Undertaken of Relevance to Marine Mammal Baseline Characterisation


4. Methodology

4.1. Desktop Study

4.1.1.    Regional Data Sources

  1. Information on marine mammals within the regional marine mammal study area was collected through a detailed desktop review of existing studies and datasets. These are summarised at Table 4.1   Open ▸ .


Table 4.1:
Key Sources of Information for the Marine Mammal Baseline Characterisation

Table 4.1: Key Sources of Information for the Marine Mammal Baseline Characterisation


4.2. Surveys

  1. A number of surveys have been conducted over the Proposed Development. This section provides an overview of each of these surveys with a summary given in Table 4.2   Open ▸ .


Table 4.2:
Summary of Survey Data

Table 4.2: Summary of Survey Data


4.2.2.    TCE Aerial Surveys for the Forth and Tay Offshore Wind Developers Group (FTOWDG) Region (Historical)

  1. Visual aerial surveys of the Scottish territorial waters (within 12 nm) and Firth of Forth and Tay Round 3 sites were commissioned by TCE (Grellier and Lacey, 2011). The transect design was based on parallel lines with equal spacing in both inshore (up to 12 nm) and offshore (greater than 12 nm) areas (Macleod and Sparling, 2011). Surveys were carried out during 24 days between May and August 2009 (summer) and November 2009 and March 2010 (winter) ( Figure 4.1   Open ▸ ). Between five and 48 sections of transects were flown in any one survey day and observed track length varied from 341 km to 1,116 km.

Figure 4.1:
Summer (Top) and Winter (Bottom) Survey Tracks Flown Within and Beyond the 12 nm Boundary in May to August 2009 and November 2009 to March 2010 (Source: Macleod and Sparling (2011))

Figure 4.1: Summer (Top) and Winter (Bottom) Survey Tracks Flown Within and Beyond the 12 nm Boundary in May to August 2009 and November 2009 to March 2010 (Source: Macleod and Sparling (2011))

4.2.3.    Seagreen Firth of Forth Round 3 Boat-Based Surveys (Historical)

Visual boat-based surveys for marine mammals and seabirds, undertaken to inform the Environmental Impact Assessments (EIAs) for Seagreen Wind Energy Limited (hereafter referred to as Seagreen) were carried out by ECON Energy. The survey area comprised the Firth of Forth Round 3 Zone, which is approximately 2,850 km2 and its boundary lies approximately 25 km offshore of the Firth of Forth. Encounter rates and distribution of sightings of marine mammals from the 19 surveys which took place between May 2010 and November 2011 were analysed and reported by SMRU Ltd (Sparling, 2012). The survey was carried out each month and followed transect lines distributed 3.7 km apart across four different routes (east, west, north and south), spaced at 300 m from each other ( Figure 4.2   Open ▸ ). The four routes were rotated with each route used once per season (i.e. every four months) to maximize coverage of the zone. Over the 19 surveys, a total of 17,017 km of survey effort was conducted. Data were analysed by DMP Statistical Solutions UK Limited using a model-based approach to estimate densities and abundances of key species (harbour porpoise Phocoena phocoena, white-beaked dolphin and minke whale) within the survey area (Mackenzie et al., 2012).

Figure 4.2:
Seagreen Firth of Forth Round 3 Survey Area (Source: Sparling (2012))

Figure 4.2: Seagreen Firth of Forth Round 3 Survey Area (Source: Sparling (2012))


4.2.4.    Seagreen Boat Based Surveys (Historical)

  1. Surveys for birds only were undertaken for what was previously known as the Seagreen Alpha/Bravo project area (and known since 2018 as ‘Seagreen’) in summer 2017 (May to August inclusive). Incidental recordings of marine mammal presence were recorded during these surveys (hereafter ‘the Seagreen boat-based surveys’), where sea state ranged between one (excellent) and four (average). A summary of the marine mammal incidental sightings was reported in the Seagreen Marine Mammal Baseline Technical Report (Seagreen, 2018).

4.2.5.    Digital Aerial Surveys (2019 to 2021)

Survey approach

  1. Aerial digital surveys of seabirds and marine mammals commenced in March 2019 and continued monthly until April 2021 with an additional survey undertaken in May 2020 and April 2021 to cover delayed surveys in April 2019 and April 2020. The surveys were conducted by HiDef from an aircraft equipped with four HiDef Gen II cameras with a set resolution of 2 cm ground sample distance (GSD) and at an altitude of 550 m above sea level (ASL). The transects followed the routes shown in Figure 4.3   Open ▸ , flying at an operational speed of 220 km per hour (equivalent to 120 knots). Position data for the aircraft were recorded using a Garmin Global Positioning System (GPS) Map 296 receiver with differential GPS to give 1 m accuracy and allowed recording updates at one second intervals to match to bird and marine mammal observations.
  2. A total of 37 transects were spaced 2 km apart across the aerial survey area, which encompasses the Proposed Development array area plus a ~16 km buffer area (hereafter referred to as ‘aerial survey area’). The aerial survey area covered a total area of 4,980 km2 ( Figure 4.3   Open ▸ ). Transects were flown to cover a total length of approximately 2,490 km each month, and data from two cameras (0.25 km combined width) were subsampled to provide a minimum target of 10.0% coverage of the total survey area and an optimum coverage of 12.5% of the total survey area (approximately 620 km2 each month). Table 3.1 in Annex A presents details of the survey effort across the survey area.
  3. Data from these surveys have been used to provide current information on species presence, distribution and abundance/densities within the survey area. Full details of the survey methodology, data processing and data analyses are provided in Annex A.

Figure 4.3:
Strip Transects at 2 km Spacing for Digital Aerial Surveys Across the Proposed Development Aerial Survey Area (March 2019 to April 2021)

Figure 4.3: Strip Transects at 2 km Spacing for Digital Aerial Surveys Across the Proposed Development Aerial Survey Area (March 2019 to April 2021)

4.3. Assumptions and Limitations

4.3.1.    Marine Mammal Observers

  1. Boat-based surveys rely on marine mammal observers to record number of marine mammals and accurately identify the individuals to the species level. Ideally, a survey team, following a standard distance sampling approach, should consist of one observer to monitor the track line, a second to monitor over distance and a third person as a scribe. The team would then be rotated to reduce the possibility of observer fatigue. The historical boat surveys (Sparling, 2012) adopted the use of only a single marine mammal observer which could potentially lead to under recording. The potential for under-recording was not an issue with the DAS as all observations within the transect strip length were recorded.

4.3.2.    Survey Tracks

  1. The historical boat-based survey data (Sparling, 2012) supplied for analysis of the marine mammal data included the start and end points for each transect covered on a given day. Positions of some sightings across the surveys suggested that the boat had deviated from a straight line (designed tracks) on occasion. Since the effort is calculated as the distance over the straight line between start and end points, it may result in a slight underestimate of the length of the survey compared to actual boat tracks and therefore a slight overestimate of encounter rates.
  2. During the DAS, there were some months when not all transects could be flown (e.g. due to technical issues or weather conditions). When this was the case, remedial action was taken to improve the effort by analysing data from additional cameras along those transects nearest to the ones that had been missed.

4.3.3.    Weather Conditions

  1. Boat based surveys are typically carried out for collecting bird and marine mammal data simultaneously. Seabird surveys are generally carried out in sea states of up to four, whilst marine mammals are surveyed only in in sea states of up to three. Therefore, it is possible that encounter rates may be biased downwards if portions of the survey were carried out in sea states above three. Harbour porpoise in particularly are difficult to record and sea states of up to two are often recommended.
  2. Sea state is less problematic for aerial surveys and surveys can effectively be carried out in sea states of up to four for both marine mammals and birds (HiDef, pers comm).

4.3.4.    Bias In Data

  1. Availability bias (where an animal is underwater and therefore not available for detection) is corrected for using an estimate of the probability that an animal is on the surface at any randomly chosen instant. The resulting correction factor is then used to estimate the total number of animals that may be present within the survey area. In the case of aerial digital surveys, animals are available for detection if they are on the surface or just below the surface (depth of detectability is dependent on water clarity).
  2. Perception bias (where an animal is on the surface but the detection is missed) is less of a limiting factor since the high definition video aerial survey captures all animals on the surface and the detection is not influenced by the ability of an observer to detect an animal.
  3. The data from all surveys provided a count of the relative numbers of each species (or species group) within the transects, however, there were no site-specific data on availability bias from any of the surveys. Therefore, published correction factors, where considered to be appropriate, were applied to data to correct for bias in data to approximate absolute numbers. Correction factors were applied to the Proposed Development aerial digital survey data and are described in Annex A.
  4. Some species are known to actively avoid vessels of any kind, either by moving away or by diving, introducing unquantifiable bias into the data collected during boat-based surveys (Palka and Hammond, 2001). It is also troublesome to record wide ranging or cryptic species, especially when making the snapshot count.

4.3.5.    Species indentification

  1. During both historical aerial (Grellier and Lacey, 2011) and boat-based (Sparling, 2012) surveys, identification to species level can be challenging, especially when an individual is submerged. On the aerial shots collected during aerial surveys only part of the animal was above the surface and on some occasions, it was not possible to distinguish between species. In the case of DAS (Annex A), given the prevalence of grey seal in this area, all unidentified seals were classed as grey seals. Similarly, unidentified cetaceans were assigned to harbour porpoise. This may lead to overestimated numbers of most abundant species and underestimation of species which were not identified.

4.3.6.    Survey Timings

  1. The aerial surveys for Firth of Forth and Firth of Tay were collected across two seasons between May 2009 and March 2010 (summer and winter) on 24 days only. The boat-based data for the Seagreen Firth of Forth Round 3 were collected on a monthly basis between May 2010 and November 2011. These data are now more than ten years old and it is possible that there may have been changes in the distribution and abundance of marine mammals in the vicinity of the Proposed Development.
  2. DAS have been conducted monthly between March 2019 and April 2021. Due to constraints outwith the control of Hi-Def, the April surveys were delayed (April 2019 and April 2020) and therefore two surveys were undertaken in May 2020; one in early May (05 May 2020) and one later in May (16 May 2020) (see section 2.5 in Annex A). It represents a snapshot over a single survey day on each month (except May 2020 as two days were covered). This survey method was agreed with stakeholders and despite it having some limitations, it is a standard practice to collect data on a single day throughout the two-year time span. Changes in sightings rates may be influenced by environmental conditions, however it has not been possible to explore this over short time frame (one day) of data collection. Therefore, whilst differences in sighting rates between months may be due to seasonal changes, environmental conditions also have the potential to influence these results.

4.4. Other Studies and Data Sources

4.4.1.    Small Cetaceans in the European Atlantic and North Sea (SCANS) Surveys

  1. The main objective of SCANS surveys was to estimate small cetacean abundance and density in the North Sea and European Atlantic continental shelf waters. The SCANS I surveys were completed in 1994, SCANS II in July 2005 and SCANS III in July 2016 and all comprised of a combination of vessel and aerial surveys. Both aerial and boat-based survey methodologies were designed to correct for availability and detection bias and allow the estimation of absolute abundance.
  2. The Proposed Development is located in the SCANS II survey area V and SCANS III survey area R, surveyed by boat and air respectively. The ship surveys in SCANS II covered a total transect length of 3,022 km and an area of 160,517 km2 (Burt et al., 2006). In 2016 the SCANS III aerial survey total search effort was 51,286.7 km and covered the surface area of 1,208,744 km2 (Hammond et al., 2021). The original SCANS III data was published in the Hammond et al. (2017) report, which has been revised following the discovery of some analytical errors and the updated version Hammond et al. (2021) is used for the purpose of this study.

4.4.2.    Joint Cetacean Protocol (JCP) Phase III Analysis

  1. The JCP Phase III analysis included 38 data sources with data from at least 542 distinct survey platforms (ships and aircraft) conducted to estimate spatio-temporal patterns of abundance of seven species of cetacean over a 17-year period (1994 to 2010) over a 1.09 million km2 prediction region from 48° N to c. 64° N and from the continental shelf edge west of Ireland to the Kattegat in the east.
  2. Species of cetaceans included in the study are harbour porpoise, minke whale, bottlenose dolphin Tursiops truncatus, short-beaked common dolphin Delphinus delphis, Risso’s dolphin Grampus griseus, white-beaked dolphin and Atlantic white-sided dolphin Lagenorhynchus acutus. Density surface models were used to predict species density over a fine scale grid of 25 km2 resolution for one day in each season in each survey year. The data are divided into regions for which seasonal estimates of abundance for winter (January to March), spring (April to June), summer (July to September) and autumn (October to December). The Proposed Development is situated within the “Firth of Forth area of commercial interest”, covering the area of 14,241 km2.

4.4.3.    JNCC Report 544: Harbour Porpoise Density

  1. Heinänen and Skov (2015) conducted a detailed analysis of 18 years of survey data on harbour porpoise around the United Kingdom (UK) between 1994 and 2011 held in the JCP database. The goal of this analysis was to try to identify “discrete and persistent areas of high density” that might be considered important for harbour porpoise with the ultimate goal of determining Special Areas of Conservation (SACs) for the species. The approach involved constructing predictive models using corrected sightings rates analysed with respect to topographic, hydrodynamic and anthropogenic covariates and then generating predicted distribution maps of density estimates for the waters around the UK. The analysis grouped data into three subsets: 1994 to 1999, 2000 to 2005 and 2006 to 2011 to account for patchy survey effort and analysed summer (April to September) and winter (October to March) data separately to explore whether distribution patterns were different between seasons.
  2. Due to the uneven survey effort over the modelled period, there was a large degree of uncertainty in modelled distributions. Additionally, the analysis presented in Heinänen and Skov (2015) relied on extensive extrapolation of survey data over space and time. Any such extrapolation is sensitive to the covariates used in models and makes the assumption that these relationships hold outside of the surveyed areas.

4.4.4.    Special Committee on Seals (SCOS)

  1. Under the Conservation of Seals Act 1970 and the Marine (Scotland) Act 2010, the Natural Environment Research Council (NERC) provides scientific advice to government on matters related to the management of seal populations through the advice provided by the SCOS. SMRU provides this advice to SCOS on an annual basis through meetings and an annual report. The report includes advice on matters related to the management of seal populations, including general information on British seals, information on their current status, and addresses specific questions raised by regulators and stakeholders. The most recent publicly available SCOS report is SCOS (2020) which presents the data collected up to 2019.

4.4.5.    SMRU Seal Surveys

  1. SMRU carries out surveys of harbour and grey seals in Scotland and on the east coast of England to contribute to the NERC’s statutory obligation under the Conservation of Seals Act 1970 through provision of scientific advice on matters related to the management of seal populations to the UK Government. SMRU surveys, as well as surveys by a number of other organisations (including NatureScot, Natural England, the Countryside Council for Wales, the National Trust and the Lincolnshire Wildlife Trust) form the routine monitoring of seal populations around the UK.
  2. Seals are widely distributed around the UK coast and most surveys are carried out from the air by either light aircraft or helicopter. All surveys are of seals that are hauled out on shore. On account of differences in the breeding behaviour of harbour and grey seals, the two species are surveyed at different times in their annual cycle.
  3. A SMRU report was commissioned to support the baseline assessment for the Proposed Development. The report provided a detailed account of grey and harbour haul outs within the vicinity of the Proposed Development based on recent surveys (Annex B). A brief account of the survey methods for each seal species is provided in the following sections.

Harbour seals

  1. Surveys of harbour seals are carried out during the summer and early autumn months. There are two types of surveys conducted: breeding counts and moult counts.
Harbour seal breeding counts
  1. Breeding seals are surveyed in June and July in a small number of areas. Breeding season surveys are carried out annually in the Moray Firth and, in recent years, in Lincolnshire and Norfolk. A very limited number of breeding season surveys have been carried out on behalf of NatureScot in areas designated as SACs for harbour seals in Scottish waters and there were no breeding surveys carried out for the colonies in the vicinity of the Proposed Development marine mammal study area. Therefore, no data was available for haul out sites considered within this report.
Harbour seal August moult counts
  1. The main population surveys are carried out when harbour seals are hauled out onshore to moult, during the first three weeks of August. To maximise the numbers of seals onshore and to reduce the effects of environmental variables, surveys are restricted to within two hours either side of afternoon low tides on days with no rain.
  2. Harbour seals inhabiting rocky shores are surveyed during the moult using a helicopter equipped with a thermal imaging camera that can detect seals on land at a distance of up to 3 km. Seals on sandbanks in the east coast estuaries (including annual counts of the Firth of Tay and Eden Estuary SAC) are usually surveyed from a fixed wing light aircraft using conventional, oblique photography.
  3. The moult counts obtained represent the number of harbour seals that were onshore at the time of the survey and are an estimate of the minimum size of the population. They do not represent the total size of the local population since a proportion of the population would have been at sea at the time of the survey.

Grey seals

  1. Grey seals aggregate in the autumn to breed at traditional colonies. Their distribution during the breeding season is very different to their distribution at other times of the year.
  2. Grey seals are surveyed during their breeding season (August to December). Most breeding colonies are surveyed by SMRU by fixed wing aerial vertical photography (Hebrides, Orkney, north Scotland the north-east Scotland, and most of the Firth of Forth) while others are surveyed by ground count by other organisations (Shetland, Inchcolm in the Firth of Forth and England). The last major survey for which data has been processed and is available is 2016, where 67 colonies were counted. The most recent complete grey seal pup production survey (covering Orkney, Inner and Outer Hebrides and the North Sea colonies) was conducted in 2019. However, data from these surveys have not been processed at the time of writing and so have not been included in this report.
  3. Grey seals are also counted during SMRU’s harbour seal August moult surveys. However, counts of grey seals during the summer months can be highly variable and, although these counts are not used as a population index, they provide useful information on the summer and non-breeding season distribution of grey seals.

4.4.6.    Designated Seal Haul Out Sites

  1. In Scotland, seals are protected under the Marine (Scotland) Act 2010. Section 6 of this Act prohibits the taking of seals except under licence. Licences can be granted for the protection of fisheries and aquaculture and for scientific and welfare reasons. The NERC, through the SCOS and the NERC sponsored SMRU, provides advice on all licence applications and haul-out designations. Section 6 of this Act also prohibits harassment and injury to seals. The Protection of Seals (Designation of Haul-Out Sites) (Scotland) Order 2014 laid in the Scottish Parliament on 26 June 2014 which, from 30 September 2014, makes it an offence to harass seals at these sites. Harassment involves any activity that pesters, torments, troubles or attacks a seal on a designated haul-out site. In particular, it would include any action that causes a significant proportion of seals on a haul-out site to leave that site either more than once or repeatedly or, in the worst cases, to abandon it permanently (Marine Scotland, 2014a; 2014b).
  2. Within or in the vicinity of the Proposed Development marine mammal study area there are two seal haul out sites (Kinghorn Rocks and Inchmickery and Cow and Calves) and three grey seal breeding colony sites (Fast Castle, Inchkeith and Craigleith) designated under this order (see Figure 6.17   Open ▸ and Figure 6.24   Open ▸ for harbour and grey seal respectively).

4.4.7.    Seal Telemetry Data

  1. SMRU has deployed telemetry tags on grey seals and harbour seals in the UK since 1988 and 2001, respectively. The telemetry tags transmit data on seal locations with the tag duration (number of days) varying between individual deployments. Telemetry data are particularly useful as they provide information on seal movement patterns away from their haul out sites, provide data on the foraging behaviour of seals at sea and demonstrate connectivity between areas.
  2. There are data from two types of telemetry tag, which differ by their data transmission methods. Data transmission can be through the Argos satellite system (Argos tags) or GPS phone tags which combine GPS quality locations with transmission of data using the Global System for Mobile communication (GSM) phone network. These methods are described in more detail in section 2.2 of Annex B.
  3. Telemetry data presented in this report draws on the SMRU commissioned study (Sinclair, 2022), which presents an analysis of existing satellite data to describe the movements of harbour and grey seal within or in the vicinity of the Proposed Development marine mammal study area (Annex B).

4.4.8.    Seal Usage Maps

  1. Carter et al. (2020) have produced revised estimated at-sea distribution usage maps for both grey and harbour seals based on habitat association modelling. The previous usage maps (Russell et al., 2017) contained telemetry data from 270 grey seals and 330 harbour seals tagged within the UK only and incorporate count data between 1996 and 2015. Carter et al. (2020) maps incorporated an additional 100 GPS telemetry tags deployed on grey seals at sites where recent tracking data were lacking. The at sea usage maps represent the number of grey and harbour seals estimated to be in the water in each 5 km x 5 km grid cell at any given time. Values in the Carter et al. (2020) report are presented as spatial predictions of relative density. For the purpose of this report, absolute densities were calculated based on the total at-sea population size for British Isles presented in Appendix 2 of Carter et al. (2020). However, there are concerns about accuracy of scalars used for the analysis (Russell et al., 2016; Lonergan et al., 2013). Therefore, the scalar to convert haul-out counts to the total population and the scalar to convert the total population to the at-sea abundance are currently being reviewed. Given the above, results of the analysis of densities presented in Carter et al. (2020) are to be taken as approximate estimates, rather than definitive numbers.

4.4.9.    The East Coast Marine Mammal Acoustic Study (ECOMMAS)

  1. The ECOMMAS began in 2013 and involved 30 PAM sites along the east coast of Scotland to collect data on the relative abundance of dolphins and porpoises. Every PAM site contained a C-POD capable of detecting dolphin and porpoise echolocation clicks and some sites also contained an acoustic recorder (SM2M) capable of recording underwater noise and the vocalisations of dolphin species.
  2. There were 15 locations along the Scottish east coast outside of the Moray Firth including three C-POD stations at each of the following locations: Cruden Bay, Stonehaven, Arbroath, St Andrews and St Abbs. Each location had PAM units placed approximately 5 km, 10 km and 15 km from the coast ( Figure 6.11   Open ▸ ).
  3. Data from these surveys was analysed, however due to it is limitations, only the main findings are presented to inform the baseline (described further in section 6.2.2).

5. Baseline Environment

5.1. Legislation and Conservation Designations

5.1.1.    Legal Framework

  1. In Scottish inshore waters (within 12 nm of the coast), the Conservation (Natural Habitats, &c.) Regulations 1994 (as amended) make it an offence to disturb a cetacean intentionally or recklessly. The Marine (Scotland) Act 2010 provides improved protection for seals. Moreover, The Marine (Scotland) Act 2010 and The UK Marine and Coastal Access Act 2009 includes provisions to designate Marine Protected Areas (MPAs) (within territorial and offshore waters respectively. In the UK, all species of marine mammals up to 12 nm are protected under the Wildlife and Countryside Act (1981). Additionally, in Scotland basking shark Cetorhinus maximus is given full protection under Schedule 5 of the Wildlife and Countryside Act 1981. Basking shark have been considered in more detail as a part of desktop study in section 4.2.1 of volume 3, appendix 9.1.
  2. A number of marine mammal species are listed in Annex II of the Habitats Directive (Council Directive 92/43/EEC) as species whose conservation requires the designation of SACs. In Scotland, Annex II marine mammal species for which SACs are designated include harbour porpoise, grey seal, harbour seal and bottlenose dolphin.
  3. Under Annex IV of the Habitats Directive, all cetacean species are afforded strict protection wherever they occur within a Member State’s territory, both inside and outside designated protected areas. These are termed European Protected Species (EPS).
  4. MPAs (also called Nature Conservation MPAs) are areas of the sea with special controls to protect species and habitats, and to support the wider marine ecosystem. A total of 35 MPAs have been designated in Scotland’s seas (NatureScot, 2021c). The development of this network has been progressed between Marine Scotland, JNCC, Natural England, Historic Environment Scotland (HES), Scottish Environment Protection Agency (SEPA) and NatureScot, along with a range of marine stakeholders.

5.1.2.    Conservation Designations

  1. A number of designated areas within the northern North Sea (i.e. regional marine mammal study area) have marine mammals as notified interest features ( Figure 5.1   Open ▸ ). Information to support a Habitats Regulation Appraisal (HRA) screening was provided for the whole of the regional marine mammal study area to determine the European sites that should be considered further in the RIAA (SSER, 2022c). In this Technical Report we present an overview of European sites that fall within the UK portion of the regional marine mammal study area or are within the central part of the northern North Sea and therefore more likely to have connectivity with the Proposed Development (as opposed to sites near to the European coastline, approximately 500 km or more from the Proposed Development). A summary of the relevant marine mammal qualifying interest and/or protected features for each site is provided in Table 5.1   Open ▸ .

Figure 5.1:
European Sites Designated for Protection of Marine Mammals Within the Regional Marine Mammal Study Area

Figure 5.1: European Sites Designated for Protection of Marine Mammals Within the Regional Marine Mammal Study Area

Table 5.1:
SACs Designated for the Protection of Marine Mammals within the Regional Marine Mammal Study Area

Table 5.1: SACs Designated for the Protection of Marine Mammals within the Regional Marine Mammal Study Area


Berwickshire and North Northumberland Coast SAC 

  1. Extending over an area of 652 km2, the Berwickshire and North Northumberland Coast SAC lies approximately 35 km from the Proposed Development array area (English Nature, 2005). This site features a range of Annex I habitats, including mudflats and sandflats not covered by seawater at low tide, large shallow inlets and bays, reefs as well as submerged and partially submerged sea caves (English Nature, 2005).
  2. The SAC embodies an extensive and diverse stretch of coastline in south-east Scotland and north-east England. The latter coastal section provides important habitats for Annex II grey seal species. The breeding colonies within this SAC consist of approximately 1,000 individuals and support around 2.5% of UK pup production (JNCC, 2015a). 

Isle of May SAC 

  1. The Isle of May SAC extends over an area of 3.5 km2 (JNCC, 2015b) and is located approximately 40 km from the Proposed Development array area. It is located at the entrance to the Firth of Forth on the east coast of Scotland and supports Annex II species, the fourth largest breeding group of grey seals in the British Isles (contributes approximately 4.5% annual UK pup production) (JNCC, 2015b). The SAC is the largest east coast breeding colony of grey seals in Scotland and comprises of up to 5,900 individuals. The annual SCOS reports suggest that the population of grey seals within this SAC is increasing (e.g. SCOS, 2019; SCOS, 2020). 

Firth of Tay and Eden Estuary SAC

  1. The Firth of Tay and Eden Estuary SAC lies approximately 47 km from the Proposed Development array area, covers an area of approximately 155 km2 and comprises of two high quality estuarine areas, which are integral components of a large, geomorphologically complex area (JNCC, 2021a). The SAC supports a breeding colony of harbour seal. From 2002 to 2017 the harbour seal count for the Firth of Tay and Eden Estuary SAC decreased rapidly at approximately 18.6% p.a. (see annex B). Subsequently, the count in 2019 for this SAC was 41 individuals, which represents a 95% decrease from the mean counts recorded between 1990 and 2002 (SCOS, 2020). Sporadic counts in the Firth of Forth indicate, however, that the decline is localised within the SAC and may not represent the trends in the overall MU population. Adults use sandbanks within this SAC as a haul out habitat to rest, pup and moult (JNCC, 2021a). Other species utilizing the SAC area include grey seal, harbour porpoise and bottlenose dolphin.

Moray Firth SAC 

  1. The Moray Firth SAC is located approximately 167 km to the north of the Proposed Development array area and supports the only known resident population of bottlenose dolphin in the North Sea (Annex II species). This SAC covers an area of 1,512 km2 and extends from the inner firths to Helmsdale on the north coast and Lossiemouth on the south coast (JNCC, 2021b). The bottlenose dolphins found in the Moray Firth SAC are part of a Scottish east coast population of 224 animals that ranges south past Aberdeen to the Firths of Tay and Forth (Quick et al., 2014; Arso Civil et al., 2021). Data from the site condition monitoring suggest that the proportion of the east coast of Scotland bottlenose dolphin population that use the SAC has declined, although the overall population along the coast is increasing (Cheney et al., 2018) and it is thought that their range is extending (Quick et al., 2014; Cheney et al., 2018; Arso Civil et al., 2019; Arso Civil et al., 2021).
  2. Other marine mammals observed regularly within this SAC include harbour porpoise, grey seal and harbour seal. The population of harbour seal consist of 501 to 1,000 individuals that occur throughout the year, breeding and resting on intertidal sandbanks in the inner Moray First and making regular foraging trips into the central and outer Moray Firth (Bailey et al., 2014). 

Dornoch Firth and Morrich More SAC

  1. The Dornoch Firth and Morrich More SAC covers an area of approximately 87 km2 (JNCC, 2015c) and lies approximately 195 km from the Proposed Development array area. The features of interest include a variety of marine features including reefs, sublittoral sandbanks and estuaries. It is located at the most northerly estuary in Britain and supports a significant proportion of the internationally important population of harbour seal (accounts for almost 2% of the UK population). This is also the most northerly population of harbour seal which utilise sandbanks as haul-out and breeding sites (JNCC, 2015c).

Southern North Sea SAC

  1. The Southern North Sea SAC, covering an area of 36,951 km2, was designated to conserve harbour porpoise (JNCC, 2021c). The majority of the site lies offshore (88%), extending into English inshore waters (12%) and it is located 146 km to the south-east from the Proposed Development array area. Population estimates within the site based on the 2016 survey are a minimum of 20,237 (lower 95% CI) and a maximum of 41,538 individuals (JNCC, 2019) The SAC area supports an estimated 17.5% of the UK North Sea MU population. The northern part supports higher densities of porpoises during the summer season (April to September), whilst the southern part is recognised as an important area during the winter season (October to March) (JNCC, 2021c).

Doggersbank SAC

  1. The Doggerbank SAC is located approximately 295 km from the Proposed Development array area and lies within Dutch waters encompassing an area of 4,735 km2 (EUNIS, 2021a). The site became a SAC in 2016. Qualifying species for the site include harbour porpoise, grey and harbour seal (EUNIS, 2021a). Conservation objectives are to maintain the distribution, extent and quality of habitat for the purposes of maintaining the population and maintain the extent and quality of habitat in order to maintain the population (BEIS, 2021).

Doggerbank Site of Community Importance

  1. The Doggerbank SCI is located in German waters, approximately 314 km from the Proposed Development array area and covers an area of 1,699 km2 (EUNIS, 2021b). Qualifying species for the site include harbour porpoise and harbour seal (EUNIS, 2021b). Conservation objectives of the site are to maintain and restore to favourable conservation status qualifying species and their habitats, and maintain and restore the site’s specific ecological functions, biodiversity and natural hydrodynamics and morphodynamics (BEIS, 2021).

Klaverbank SAC

  1. The Dutch Klaverbank (Cleaver Bank in English) is located approximately 332 km from the Proposed Development array area. It extends over 1,539 km2 in a transboundary area shared between the UK and the Netherlands (Álvarez et al., 2019). Grey seal, harbour seal, and harbour porpoise are all qualifying interest features of this site, but it is also known to host minke whales and white-beaked dolphin during summer months (Álvarez et al., 2019). The population size of the qualifying species has not been identified. Conservation objectives are to maintain the distribution, extent and quality of habitat for the purposes of maintaining the population and maintain the extent and quality of habitat in order to maintain the population (BEIS, 2021). Studies suggested that little is known about the Dutch North Sea grey seal population because, albeit most seals spend the majority of their time close to their central place, they travel large distances along the continental coast and to/from the UK (Brasseur et al., 2010). There are estimated to be approximately 1,700 grey seals in the Dutch North Sea (Noordzeeloket, 2021a). During historical aerial survey, a high density of grey seal was observed in the Klaverbank SCI (the site was designated as SAC in June 2016), particularly to the north of the site (Deerenberg et al., 2010).
  2. The harbour seal is the most abundant seal species in the Netherlands, with an estimated 6,000 individuals inhabiting the Dutch section of the North Sea and Wadden Sea (Noordzeeloket, 2021b). In the Klaverbank SAC, a harbour seal density of 0.46 to 0.6 animals per km2 were observed (Deerenberg et al., 2010).
  3. The harbour porpoise occurs regularly in Dutch waters, either alone or in small groups. There has been an increase in sightings in this area since 1990; the current population estimate in Dutch waters lies between 15,000 and 19,000 individuals. During historical aerial survey, a harbour porpoise density of 0.46 to 0.6 individuals per km2 were recorded within majority of the site. However, to the north of the site, a higher density was estimated (1.06 to 1.25 individuals per km2) (Deerenberg et al., 2010).Overview of Marine Mammals

5.1.3.    Regional Marine Mammal study area

  1. The northern portion of the North Sea is an important area for cetaceans, with both numbers and species diversity decreasing towards the south (Weir, 2001). It regularly supports 11 species of cetaceans and two species of pinnipeds (Weir, 2001; Hammond et al., 2013; Hammond et al., 2021; NMPI, 2021). The distribution of marine mammals is strongly influenced by the distribution of their prey. Higher abundance of cetaceans in the north may be correlated with presence of pelagic species, which enter the North Sea via northern area adjacent to deep Atlantic waters along the continental shelf edge (Weir, 2001). The occurrence of cetacean species is often unpredictable due to their highly mobile nature. Although the distribution of marine mammals in the North Sea is patchy, some areas consistently hold a higher number of species.
  2. The east coast of Scotland and north-east of England support multiple haul-out sites for both grey seal and harbour seal and densities of these species might be expected to be higher in the vicinity of these areas at certain times of the year (Hammond et al., 2002; Weir, 2001).
  3. Within the coastal waters of the east of Scotland, the more commonly recorded cetaceans include harbour porpoise, bottlenose dolphin, white-beaked dolphin, and minke whale. Other species of cetacean have been recorded as occasional or rare visitors to this region ( Table 5.2   Open ▸ ).


Table 5.2:
Summary of Cetacean Species Found in the Regional Marine Mammal Study Area. Sources: Weir (2001), Hammond et al. (2013), Hammond et al. (2021) and NMPI (2021)

Table 5.2: Summary of Cetacean Species Found in the Regional Marine Mammal Study Area. Sources: Weir (2001), Hammond et al. (2013), Hammond et al. (2021) and NMPI (2021)


5.1.4.    Proposed Development Marine Mammal Study Area

  1. Data from surveys conducted within the Firth of Forth ( Table 4.2   Open ▸ ) demonstrate that several marine mammal species occurred regularly within the Proposed Development marine mammal study area. Harbour porpoise was the most frequently recorded cetacean during the aerial and boat-based surveys and was recorded in every month of the year. Other species recorded during the surveys within the Proposed Development marine mammal study area included minke whale and white-beaked dolphin (both with seasonal occurrence during spring/summer months), grey seal (year-round) and harbour seal (only three sightings recorded to species level). Only a small number of bottlenose dolphin were observed during DAS (two sightings with a total of seven individuals); however, the Proposed Development marine mammal study area is situated in close proximity to the east coast of Scotland population range for this species and therefore their presence within the Proposed Development marine mammal study area could not be precluded.

5.2. Proposed Development Aerial Digital Survey Data Analysis

  1. This section refers to DAS undertaken by HiDef, across the aerial survey area. The aerial digital surveys commenced in March 2019 and were undertaken monthly, with a total of 25 months of data collected up until April 2021.