Appendix 9 Marine Mammals – Baseline Environment

9.1.        Desktop Study

236. A number of key datasets and desktop reports have been identified to support this Scoping Report for marine mammals. These are summarised in Apx Table 9.1   Open ▸ .

Apx Table 9.1:  Summary of Key Desktop Reports to Inform Marine Mammal Scoping Assessment

9.2.        Site-specific Survey Data

237. Site-specific aerial surveys across the Array marine mammal study area have been conducted monthly since March 2021, and due to be completed in February 2023. While the dataset has not been fully analysed yet, preliminary counts of sightings from March 2021 to September 2022 are available and have been included within the baseline characterisation. Upon completion of the surveys in February 2023 and the full dataset will be analysed, and used to inform the assessment within the Array EIA Report.
238. There were 1,000 marine mammal sightings overall, with harbour porpoise Phocoena phocoena comprising the majority of sightings (n=825). White-beaked dolphin Lagenorhynchus albirostris, was the second most abundant species (n=72), followed by grey seal Halichoerus grypus (n=26), and minke whale Balaenoptera acutorostrata (n=16). In addition, there were 46 unidentified marine mammals, four common dolphins Delphinus delphis, and three harbour seal Phoca vitulina recorded. However, common dolphins and harbour seal were classed as rare or occasional visitors to the area and will not be carried forward in the assessment. Marine mammal observations during these aerial surveys are shown in Apx Figure 9.1   Open ▸ to Apx Figure 9.5   Open ▸ .

Apx Figure 9.1: Marine Mammals Sightings Recorded Between March and June 2021

Apx Figure 9.2: Marine Mammals Sightings Recorded Between July and October 2021

Apx Figure 9.3: Marine Mammals Sightings Between November 2021 and March 2022

Apx Figure 9.4: Marine Mammals Sightings Between March and July 2022

Apx Figure 9.5: Marine Mammals Sightings Between August and September 2022

9.3.        Baseline Characterisation

9.3.1      designated Sites

239. There are several designated sites with marine mammal features in the vicinity of the Array ( Apx Figure 9.6   Open ▸ , Apx Table 9.2   Open ▸ ). These sites may require consideration within the EIA and Habitats Regulation Assessment (HRA). The Likely Significant Effect (LSE) Report will include a full screening of National and European designated sites with qualifying marine mammal interest features that may be impacted by the Array. Any relevant sites and/or features screened into the marine mammal assessment will be assessed in the marine mammal chapter of the Array EIA Report. The information to support the assessment of transboundary European sites and features will be presented in the Report to Inform Appropriate Assessment (RIAA).

Apx Table 9.2:  Summary of Protected and/or Designated Sites with Marine Mammal Features in Proximity to the Array

Apx Figure 9.6: Sites Designated for Marine Mammal Features and Other Offshore Infrastructure Within Close Proximity to the Array

9.3.2      Target Species

240. The following section summarises abundance estimates of the four marine mammal species that are present below Mean Low Water Springs (MLWS) that are likely to occur within the Array marine mammal study area and the regional marine mammal study area: harbour porpoise, minke whale, white-beaked dolphin and grey seal. Grey seals at haul-out sites are the only marine mammal receptors that are at risk of impacts above MLWS. Seal-haul out sites will therefore be important to consider in terms of potential impacts from landfall activities, however as this Scoping Report focusses on the Array only and does not cover impacts relevant to export cable corridor(s) and landfall location(s), these sites will not be considered.
241. Other marine mammal species have been recorded within or in close proximity to the Array marine mammal study area and the regional marine mammal study area. For example, there were four common dolphins sighted during the site-specific surveys for the Array in 2021, with three individuals recorded in July and one in September. Additionally, there were three harbour seals sighted during the site-specific surveys for the Array, with two individuals recorded in April 2021 and one in May 2022. Harbour seal are a more coastal species than grey seal, as they primarily stay within 50 km of the coastline and typically feed within 40 km to 50 km of their haul out sites (Jones et al., 2015; SCOS, 2021). Due to this, there is little potential connectivity between the Array area and harbour seal haul-out sites. Harbour seal distribution at sea is illustrated in Apx Figure 9.7   Open ▸ and Apx Figure 9.8   Open ▸ , based on Carter et al. (2022), and telemetry tag data provided by SMRU. Harbour seal density within the Array marine mammal study area is low, with values between >0 to 1 animal per 25 km2 (Carter et al., 2022; Apx Figure 9.7   Open ▸ ). As illustrated in Apx Figure 9.8   Open ▸ , harbour seals have a close coastal distribution, however four tagged individuals were recorded overlapping with the Array marine mammal study area. Furthermore, harbour seal were the least abundant marine mammal observed during the Berwick Bank Offshore Wind Farm surveys (n= 3 individuals; SSER, 2022) and Firth of Forth Round 3 surveys (n=24 individuals; Sparling, 2012), which were further inshore than the Array. Overall, given the available data, harbour seal are considered to be an occasional visitor within the Array marine mammal study area, and are not carried forward in the assessment.
242. There were a low number of white-sided dolphins and one Risso’s dolphin Grampus griseus recorded within the regional marine mammal study area in the most recent SCANS-III survey (Hammond et al., 2017, 2021). Killer whale Orcinus orca, common dolphin and pygmy sperm whale Kogia breviceps have also been recorded as rare or occasional visitors to the regional marine mammal study area in a now dated publication (Reid et al., 2003). One sighting of a group of ten white-sided dolphins was observed during site-specific boat-based surveys conducted during Firth of Forth Round 3 surveys for the nearby Seagreen 1 Offshore Wind Farm (Sparling, 2012), and one common dolphin, one killer whale and a group of eight long-finned pilot whales Globicephala melas, were observed in aerial surveys for Seagreen’s regional study area (Grellier and Lacey, 2012). There were no bottlenose dolphin sightings recorded during the site-specific surveys covering the Array. However, they were recorded, albeit in low abundance (n=7 individuals) on two occasions over the 25-month course of site-specific aerial surveys between 2019 and 2021 for the Berwick Bank Offshore Wind Farm (SSER, 2022). There were no bottlenose dolphin sightings during the Firth of Forth Round 3 surveys (Sparling, 2012), and three individuals recorded during aerial surveys for the FTOWDG region (Grellier and Lacey, 2012). Due to low likelihood of occurrence and their rarity in the regional marine mammal study area, common dolphin, white-sided dolphin, bottlenose dolphin, Risso’s dolphin, killer whale, pygmy sperm whale, and long-finned pilot whale are not included in the characterisation of the marine mammal baseline and are not carried forward in the assessment.

Apx Figure 9.7: Harbour Seal At Sea Usage within the Vicinity of the Array (Source: Carter et al., 2022)

Apx Figure 9.8: Telemetry Tracks for Tagged Harbour Seals (Source: Sinclair, 2021)

243. Management Units (MUs) will be used to inform the regional marine mammal study area. The MUs for harbour porpoise, white-beaked dolphin and minke whale were defined by the Inter-Agency Marine Mammal Working Group (IAMMWG, 2015, 2022). The most recent IAMMWG report provided updated estimates for these species and their MUs based on the most recent datasets, notably SCANS-III (Hammond et al., 2017), and Rogan et al. (2018). The MUs for grey seal were defined by the Special Committee on Seals (SCOS), who publish annual information on August haul out counts, pup counts and population estimates (SCOS, 2021). The different MUs for the target species are presented in Apx Figure 9.9   Open ▸ .

Harbour porpoise

244. Hague et al. (2020) present information on regional baselines for marine mammals across the regional marine mammal study area, based on collation of over 40 data sets. They propose that harbour porpoises are resident and abundant year-round in Scottish waters (Hague et al., 2020). The most recent assessment concluded that the overall Conservation Status of harbour porpoises in UK waters is Unknown, and that there was insufficient data to calculate trends in the population size and future prospects (Joint Nature Conservation Committee (JNCC), 2019a). The Array marine mammal study area is located within the North Sea MU for harbour porpoise (IAMMWG, 2022), which has an estimated abundance of 346,601 individuals (CV: 0.09, 95% CI: 289,498 to 419,967) based on estimates from the SCANS-III survey (Hammond et al., 2017, 2021). All three SCANS surveys (1994, 2005, and 2016) reported harbour porpoise as the most frequently sighted cetacean in Scottish waters, with sightings in all survey blocks (Hammond et al., 2002, 2006, 2017, 2021, cited in Hague et al., 2020).
245. The SCANS-III density estimate was 0.599 individuals per km2 (CV: 0.287) for the relevant survey block (Block R; Hammond et al., 2017, 2021). The predicted density surface of harbour porpoise in the Array marine mammal study area is between 0.5 to 1.2 animals per km2 (Appendix 3 by Lacey and Hammond in Hague et al., 2020). The analysis of results from the site-specific aerial surveys conducted for the nearby Berwick Bank Offshore Wind Farm, reported a mean density estimate of 0.24 animals per km2 (95% CL: 0.063 to 0.472) across all months (SSER, 2022).
246. While the SCANS-III survey and previous SCANS surveys between 1994 and 2016 are the most recent broad scale datasets for harbour porpoise within both the Array marine mammal study area and the regional marine mammal study area, they only reflect summer distribution. However, sightings data between 1980 and 2018 collated by Waggitt et al. (2020) report year-round abundance of harbour porpoise, with increased density in the summer months. This is consistent with the results of the site-specific aerial surveys conducted for the nearby Berwick Bank Offshore Wind Farm, which reported higher densities during spring and summer than in autumn and winter (SSER, 2022).
247. Harbour porpoise were the most abundant marine mammal recorded during the site-specific surveys for the Array, with a total of 825 individuals sighted between March 2021 and September 2022. They were the only species to be observed during all the monthly surveys, with the highest number of individuals observed in July 2021 (n=187). They were also the most abundant marine mammal recorded during the 25-month course of site-specific aerial surveys conducted between 2019 and 2021 for the Berwick Bank Offshore Wind Farm, with a total of 2,034 individuals observed (56.77 km from site boundary; SSER, 2022). There were 174 individuals recorded during the Firth of Forth Round 3 surveys conducted for the nearby Seagreen 1 Offshore Wind Farm (50.72 km from the site boundary; Sparling, 2012). Given their recorded abundance in the literature and recent site-specific surveys for the Array and nearby offshore wind farms, harbour porpoises are considered likely to occur within the Array marine mammal study area and regional marine mammal study area all year round.  

Apx Figure 9.9: Management Units for Relevant Marine Mammal Species in the Vicinity of the Array

Minke whale

248. The Hague et al. (2020) report concludes that minke whales are present in Scottish waters mainly in the summer, and are considered to be seasonal visitors, however, there have been some sightings year-round. Waggitt et al. (2020) reported large seasonal variation in minke whale densities, with much higher densities in the summer than the winter. The most recent assessment concluded that the overall Conservation Status of minke whales in UK waters was Unknown, and that there was insufficient data to calculate trends in the population size and future prospects (JNCC, 2019b). All minke whales in UK waters are considered to be a part of the Celtic and Greater North Seas MU (IAMMWG, 2022). This MU has an estimated abundance of 10,288 individuals in the UK portion (CV: 0.26, 85% CI: 6,210 to 17,042) and 20,118 individuals in the entire MU (CV: 0.18, 95% CI: 14,061 to 28,786) based on estimates from the SCANS-III survey (Hammond et al., 2017, 2021) and ObSERVE survey (Rogan et al., 2018).
249. The SCANS-III density estimate was 0.0387 individuals per km2 (CV: 0.614) for the relevant survey block (Block R; Hammond et al., 2017, 2021). The predicted density surface of minke whale in the Array marine mammal study area is between 0.03 to 0.05 animals per km2 (Appendix 3 by Lacey and Hammond in Hague et al., 2020). An overall mean relative density of 0.004 animals per km2 (CV: 1.01) and absolute density of 0.009 animals per km2 was calculated based on the results from site-specific aerial surveys at the nearby Berwick Bank Offshore Wind Farm (SSER, 2022).
250. Minke whales were observed in the summer only during the site-specific surveys, with eight individuals recorded across June and July in 2021, and eight individuals recorded across June and July in 2022. Similarly, minke whales were observed relatively often during the summer months in the site-specific aerial surveys for Berwick Bank Offshore Wind Farm (n=57 individuals; SSER, 2022) and Firth of Forth Round 3 Zone surveys (n=62 individuals, Sparling, 2012). Based on these results and the wider literature, minke whales are considered likely to occur regularly in the summer months within the Array marine mammal study area and regional marine mammal study area. 

White-beaked dolphin

251. The most recent assessment concluded that the overall Conservation Status of white-beaked dolphins in UK waters was Unknown, and that there was insufficient data to calculate trends in the population size and future prospects (JNCC, 2019d). All white-beaked dolphins in UK waters are considered to be a part of the Celtic and Greater North Seas MU (IAMMWG, 2022). This MU has an estimated abundance of 34,025 individuals in the UK portion (CV: 0.28, 85% CI: 20,026 to 57,807) and 43,951 individuals in the entire MU (CV: 0.22, 95% CI: 28,439 to 67,924) based on estimates from the SCANS-III survey (Hammond et al., 2017, 2021) and ObSERVE survey (Rogan et al., 2018).
252. The Hague et al. (2020) report concludes that white-beaked dolphins are resident and abundant in Scottish waters year-round, with a tendency to occupy near to offshore waters. The analysis by Waggitt et al. (2020) reported year-round abundance in the Array marine mammal study area and regional marine mammal study area, with an increase in abundance in the summer months. This is consistent with the results of the site-specific aerial surveys conducted for the nearby Berwick Bank Offshore Wind Farm, which reported white-beaked dolphin sightings in the summer months only, with an overall mean density of 0.004 animals per km2, (CV: 0.79) and an approximated absolute density of 0.022 animals per km2 (SSER, 2022). The predicted density surface of white-beaked dolphin in the Array marine mammal study area is between 0.05 to 0.2 animals per km2 (Appendix 3 by Lacey and Hammond in Hague et al., 2020). Furthermore, the SCANS-III density estimate was 0.243 individuals per km2 (CV: 0.484) for the relevant survey block (Block R; Hammond et al., 2017, 2021).
253. White-beaked dolphins were the second most abundant marine mammal observed during the site-specific surveys covering the Array, with a total of 72 individuals sighted across ten surveys between March 2021 and September 2022. They were observed between March to October, with highest numbers recorded in June and July (n=18 and 19, respectively). Based on these results, the wider literature, and sightings recorded during the Berwick Bank Offshore Wind Farm surveys (n=45 animals; SSER, 2022), and from previous surveys in the Firth of Forth Round 3 (n= 221 animals; Sparling, 2012), white-beaked dolphins are considered likely to occur regularly (mostly likely in the summer months) within the Array marine mammal study area and the regional marine mammal study area.

Grey seal

254. The Hague et al. (2020) report concludes that grey seals are year-round residents in Scottish waters and are distributed further offshore than harbour seals. The most recent assessment concluded that the Conservation Status was of grey seals in UK waters was Favourable, with the overall trend in Conservation Status assessed as Improving and Future Prospects assessed as Favourable (JNCC, 2019e). The Array marine mammal study area is situated within the East Scotland MU (SCOS, 2021). There is also potential overlap between other seal MUs on the east coast of the UK, such as the Northeast England MU, or Moray Firth MU. This is due to extensive offshore foraging trips undertaken by grey seals, which have been recorded undertaking foraging trips up to and over 100 km offshore using corridors between haul out sites for up to 30 days (Jones et al., 2015, SCOS, 2021). A now dated study by McConnell et al. (2001) reported one tagged grey seal undertaking a long distance excursion of 2100 km over 64 days, making several stops at established haul out sites along the route.
255. Grey seal distribution at sea is illustrated in Apx Figure 9.10   Open ▸ and Apx Figure 9.11   Open ▸ based on Carter et al. (2022), and telemetry tag data provided by SMRU. Grey seal at sea usage is low throughout most of the site boundary, with between >1 to 5 animals per 25 km2 reported for approximately two thirds of the Array marine mammal study area. In the western edge of the Array marine mammal study area, this increases to >5 to 10 animals per animals per 25 km2, with small patches where density reaches >10 to 50 animals per 25 km2 (Carter et al., 2022; Apx Figure 9.10   Open ▸ ). As illustrated in Apx Figure 9.11   Open ▸ , grey seals are wide ranging, with a moderate number of telemetry tracks overlapping with the Array marine mammal study area.
256. The most recent population estimate of grey seals in Scotland at the start of the breeding season (before pups are born) was 120,800 individuals in 2020, and 157,300 in the wider UK (SCOS, 2021). The most recent estimated pup production from 2019 was 54,050 pups in Scotland and 67,850 in the wider UK (SCOS, 2021). The overall pup production in the wider UK increased by <1.5% per year between 2016 and 2019, with increases mainly limited to North Sea colonies along the east coast of Scotland and England (SCOS, 2021). The frequently surveyed Firth of Forth colony had an increase in pup production from 6,426 pups in 2016 to 7,261 in 2019 (SCOS, 2021). Similarly, the Farne Islands colony in the Northeast England MU had an increase in pup production between 2016 to 2019, from 2,295 to 2,823 respectively (SMRU, 2022a).
257. Counts of seals hauled out during August are used to estimate the total sizes of populations with the number of individuals hauled out estimated to be around 23.9% (95% CI: 19.2 to 28.6%) of the population (Russell et al., 2016, cited in Morris et al., 2021).  August haul out counts for the East Scotland MU have increased from 2,328 individuals during the 1996-1997 survey to 3,683 in the 2016-2019 survey (Morris et al., 2021). These counts account for 14% of grey seals hauled out in Scotland and 9% of grey seals hauled out in the UK between 2016 and 2019. August haul out counts for the Moray Firth MU population increased from 551 individuals in the 1996-1997 survey to 1,917 in the 2011-2015 survey, with a decrease to 1,657 in the 2016-2019 survey (Morris et al., 2021). There are infrequent counts for the Northeast England MU, with grey seals primarily present in the Northumberland and The Tees areas. These counts show a significant increase from 613 individuals in the 1996-1997 period to 6,565 in the 2016-2019 period (SMRU, 2022b).
258. Grey seals were observed year-round during the site-specific surveys, with a total of 26 individuals recorded over ten surveys between March 2021 and September 2022. June 2021 had the highest number of grey seals sighted (n=6), with numbers ranging between one to four individuals in other months. Grey seals were the most abundant marine mammal observed during the Firth of Forth Round 3 surveys, with 992 individuals recorded, in addition to 97 unidentified seal species (Sparling, 2012). In addition, there were 180 grey seals, 54 unidentified seals or small cetaceans and 464 unidentified seals recorded during the Berwick Bank Offshore Wind Farm surveys (SSER, 2022). Given these recordings and the available literature, grey seals are considered likely to occur year-round within the Array marine mammal study area and regional marine mammal study area. 

Apx Figure 9.10: Grey Seal At Sea Usage within the Vicinity of the Array (Source: Carter et al., 2022)

Apx Figure 9.11: Telemetry Tracks for Tagged Grey Seals (Source: Sinclair, 2021)