Seasonality

  1. During the historic TCE aerial surveys sightings of white-beaked dolphins were more common in summer (0.0061 sightings per km) than in winter (0.0015 sightings per km) (Grellier and Lacey, 2011). These results were corroborated by historic boat-based surveys, where the highest rates of white-beaked dolphins were seen in the summer months, although low numbers were also seen during surveys in September/October/December 2010 and January 2011 (Sparling, 2012). This seasonal peak is in line with a previous study that also found white-beaked dolphin to be present in Aberdeenshire waters during June to August with the main peak in August (Weir et al., 2007). The Seagreen boat-based surveys in summer 2017 recorded white-beaked dolphins on two of the five surveys: two animals were sighted on the 20 and 21 June 2017 and 17 animals on the 25 and 26 July 2017. A single dolphin of unidentified species was sighted on the 9 and 10 May, the 25 and 26 July and 15 and 16 August 2017 (Seagreen, 2018).
  2. White-beaked dolphin sightings were recorded during the DAS during summer months only, between June and September each year, with peak sightings in September 2020, which is in line with historic survey results presented above.
  3. The mating season for white beaked dolphin is in July and August with the gestation period lasting about 11 months (Culik, 2010).

6.2.4.    Minke Whale

Ecology

  1. Minke whale is the most frequently sighted mysticete (baleen whale) species in UK waters and is particularly common around the Northern Isles and in regions of the North Sea (Weir, 2001). Minke whales typically live up to 60 years with male minke whales reaching sexually maturity at the age of five to eight years and females at the age of six to eight years. In the northern hemisphere, mating occurs between October to March and the gestation period lasts approximately ten months, with the peak birth period between December and January (Seawatch Foundation, 2012). Calves usually nurse for a period of four to six months.
  2. This species tends to be observed either solitarily or in pairs or threes. However, in higher latitudes, including Northern Scotland, larger groups of ten to 15 individuals can be observed, particularly in areas of high prey density (Anderwald and Evans, 2007). Mostly inhabiting continental shelf waters, this species occurs in depths of less than 200 m and can often be seen close to land. This species is often known to exploit prey resources through other species that herd prey, enabling a low energy foraging strategy. Some regional differences exist with respect to diet (Robinson et al., 2007). Minke whale follow prey distribution and sandeel are the key food resource throughout the North Sea, with sprat, shad and herring also preferred prey items (Robinson and Tetley, 2005). Samples taken from the stomach contents of specimens within the North Sea determined that in UK waters the dominant prey items were sandeels, followed by clupeids Clupeidae and to a lesser extent mackerel Scomber scombrus (Robinson et al., 2007). Around Scotland (including Moray Firth) the primary constituent (70% of the diet of minke whales was the sandeel (Tetley et al., 2008).

Distribution and occurrence

  1. In UK waters, minke whales are distributed mainly around Scotland and in the northern and central North Sea reaching south to the Yorkshire coast (Robinson et al., 2007). By far the most sightings within continental shelf waters occur between May and September, with peak numbers from July to September, depending on the region (Evans et al., 2003). There are no obvious latitudinal trends in migration and distribution based on the Sea Watch database, although sightings in the north and east of Scotland have increased since 1990s (Evans et al., 2003), most likely due to an increase in prey availability.
  2. Data from boat-based studies carried out between May and October 2001 to 2006 in Moray Firth showed that spatial and temporal distribution of minke whales was highly variable and non-uniform (Robinson et al., 2009). Monthly encounter rates were highly inconsistent from one year to the next, with annual encounter frequencies ranging from 0 to 0.042 individuals per km across the 6-year study period. Robinson et al. (2009) highlighted that such variability is common in studies of baleen whales on their feeding grounds. From the GIS analyses, however, over 70% of the whales recorded in the Moray Firth study area occurred in steeply sloped areas at depths of between 20 m and 50 m. The arrival of whales in the study area each year appears to be synchronised with the emergence of sandeels into the water column to feed, and in the GIS results over 66% of the whale encounters showed a clear spatial preference for sandy-gravel sediments (i.e. optimal sandeel habitat (Robinson et al., 2009)). The study proved strong correlation of the sediment type with the distribution of whales.
  3. During the historic TCE aerial surveys minke whales were encountered throughout the survey area, with slightly more sightings in the northern part of the survey area ( Figure 6.15   Open ▸ ; Grellier and Lacey, 2011). Sixty-two minke whales were recorded during surveys between 2010 and 2011 with the average encounter rate of 0.003 individuals per km and highest encounter rate in May 2010 with 0.017 individuals per km. Minke whales were mostly recorded as single animals, although three animals were sighted together in May 2010 and two in June 2011.
  4. During the DAS, minke whales were recorded throughout the Proposed Development marine mammal study area (see Figure 3.4 to Figure 3.10 in Annex A). However, the mean encounter rate for minke whale was comparatively low with 0.001 (95% CI = 0.0003 to 0.002) animals per km due to their seasonality.

Density/abundance

  1. All minke whales in UK waters are considered to be part of the CGNS MU ( Figure 6.14   Open ▸ ). Based on the most up to date estimates, the abundance of minke whales in this MU is 20,118 animals (CV = 0.18, 95% CI = 14,061 to 28,786; IAMMWG, 2021). These values are lower comparing to the previous estimates from IAMMWG (2015) with 23,528 animals (95% CI = 13,989 to 39,572). However, it has been suggested that IAMMWG (2015) abundance estimates are likely to be underestimated due to the SCANS II aerial survey estimate not being corrected for perception bias and the Cetacean Offshore Distribution and Abundance (CODA) estimate not being corrected for either perception or availability bias. The SCANS III estimated abundance for block R ( Figure 6.6   Open ▸ ) was 2,498 minke whales (CV = 0.61, 95% CI = 604 to 6,791) with an estimated density of 0.0387 individuals per km2 (Hammond et al., 2021).
  2. The JCP Phase III analyses presented abundances for minke whales in 2010 by season for the Firth of Forth area of commercial interest region ( Figure 6.7   Open ▸ ) estimated highest abundance in the summer months at 360 (97.5% CI = 140 to 990) animals, with low estimates in all other seasons (20 animals during autumn and winter). This equates to density estimates between 0.025 individuals per km2 and 0.001 individuals per km2. Additionally, the study reported predicted abundance of minke whales in Firth of Forth as a percentage of the predicted number from CGNS MU, based on estimated for summers 2007 to 2010 as 1.4% (97.5% CI = 0.6 to 2.3). However, as stated by Paxton et al. (2016), the abundance estimates produced by the JCP Phase III modelling will be less reliable than those obtained from a well-designed dedicated abundance survey given the assumptions made when standardizing the data and the spatial and temporal patchiness of the data available.
  3. Integrated analysis of FTOWDG aerial (Grellier and Lacey, 2011) and Seagreen Firth of Forth Round 3 (Sparling, 2012; Figure 6.15   Open ▸ ) specific boat-based surveys data was able to generate spatially explicit absolute densities, although these were very low. Absolute abundance across the survey period and area was estimated as 594 but also showed a high level of uncertainty due to the low number of sightings (95% CI = 483 to 2695). An availability bias correction factor applied to this analysis for minke whale was 0.04 (Mackenzie et al., 2012).
  4. The greatest number of minke whales counted from the Seagreen boat-based surveys was 13 animals on the 25 and 26 July 2017 where two unidentified whales were also recorded. No minke whales were sighted during the June survey and only one animal per survey was recorded on the 9 and 10 May, 24 and 25 May and 15 and 16 August 2017 (Seagreen, 2018).
  5. Mean monthly density of minke whale based on the Proposed Development aerial digital survey data was estimated as 0.007 (95% CI = 0.004 to 0.010) animals per km2. Correcting this for availability bias using dive profile data from a visual tracking study in Iceland (McGarry et al., 2017), provided an absolute density of 0.016 (95%CI = 0.009 to 0.023) animals per km2 (section 3.5.3 in Annex A).

Figure 6.15:
Positions of Minke Whale Sightings Across All Seasons During Firth of Forth Round 3Boat Based Surveys from May 2010 to November 2011 (Sparling, 2012)

Figure 6.15: Positions of Minke Whale Sightings Across All Seasons During Firth of Forth Round 3
Boat Based Surveys from May 2010 to November 2011 (Sparling, 2012)

Seasonality

  1. Boat-based surveys carried out between May and October 2001 to 2006 in Moray Firth reported that minke whales were encountered each month with a peak in annual occurrence from July to August (Robinson et al., 2009). The distribution of whales showed a progressive inshore movement of animals across the summer and autumn months and then a progressive return to offshore waters again towards the end of the study period at which time whales were evidently less abundant, although the timing of this inshore-offshore movement was clearly variable from one year to the next. The results of this study suggest that while sandeels in the Moray Firth are highly targeted by minke whales in summer months, offshore populations of pelagic herring and sprat may also be equally or sometimes even more accessible to foraging whales at certain periods across the summer or from one year to the next, as this would explain the seasonal inshore-offshore movements and inter-annual variability of animals.
  2. Rish et al. (2019) analysed the presence of minke whale pulse trains by automated detectors developed across ten sites (from southern edge of St. Abbs to northern Moray Firth) from May to November 2016 and at Helmsdale from May 2015 to January 2018. During the study, across the whole array and all years, minke whale pulse trains were first detected in late May and detections generally declined at the end of October. During autumn and spring, minke whale pulse train detections showed strong diel periodicity, with calling rates being lowest during daylight and highest during the night. Diel variation in baleen whale vocalisations has also been attributed to prey distribution, with reduced vocalisation rates during active feeding and an increase in vocalisations in a social context at hours of lowest prey availability (Rish et al., 2019). Minke whale main prey items, such as sandeel species, show a strong diurnal pattern and are generally less available in the water column during the night (Rish et al., 2019).
  3. The observations from historic Firth of Forth Round 3 boat-based surveys conducted between 2010 and 2011 are in line with previous studies of Aberdeenshire coastal waters that reported minke whales to be highly seasonal in occurrence with sightings mainly in the summer months (Sparling, 2012). Encounter rates were highest in the spring and summer and relatively low in autumn and winter. Similar pattern was reflected in the Neart na Gaoithe boat-based surveys between 2009 and 2012 with sightings recorded only between May and November (Neart na Gaoithe, 2018).
  4. Minke whale sightings were recorded during DAS between April and September each year with peak sightings in July both years, which is in line with results of studies presented in paragraph 147 et seq.

6.3. Pinnipeds

6.3.1.    Harbour Seal

Ecology

  1. Harbour seal is the smaller of the two species of pinniped that breed in the UK, typically weighing between 80 to 100 kg (SCOS, 2015). Female harbour seal become sexually mature at three to five years of age and gestation lasts between 10.5 and 11 months (Thompson and Härkönen, 2008). Harbour seal are long-lived animals with individuals estimated to live to between 20 and 30 years (SCOS, 2018).
  2. Harbour seals, are central place foragers, requiring haul-out sites on land for resting, moulting and breeding, and dispersing from these sites to forage at sea. In order to reduce time and energy searching for prey, animals are likely to travel directly to areas of previously or predictably high foraging success (Bailey et al., 2014). Harbour seals persist in discrete metapopulations and tend to stay within 50 km of the coast, although most foraging trips are over shorter ranges (Russell and McConnell, 2014). This finding is supported by tagging studies of seals in the UK (SCOS, 2018). Since females need to regularly return to their pups at the haul-out site they may be more limited in foraging distance. Because of the constraint on their foraging range, particularly during the breeding season, harbour seals may be particularly vulnerable to changes in prey abundance or disturbance events from human activities (Bailey et al., 2014).
  3. Harbour seal breed in small groups scattered along the coastline. In north-east Scotland, the Dornoch Firth and Morrich More SAC supports an internationally important population of harbour seal, which utilise sandbars and shore as breeding sites. Pups are born in June and July having moulted their white coats prior to birth. This allows harbour seal pups to swim within a few hours of birth (Burns, 2002). During lactation, females spend much of their time in the water with their pups and, although they will forage during this period, distances travelled at this time are more restricted than during other periods (Thompson et al., 1994). Following the spring/summer breeding and nursing season, the annual moult of harbour seals in Scotland occurs from August through September (Thompson et al., 2019).
  4. Harbour seal are generalist feeders and their diet varies both seasonally and from region to region (Hammond et al., 2001). The analysis of stable isotopic composition and concentration of Hg and Se ions in blood of harbour seals from the North Sea demonstrated that harbour seals diet is comprised of 30% juvenile cod, 29% of plaice Pleuronectes platessa and 23% of monkfish Lophius piscatorius as well as European hake Merluccius merluccius and haddock (Demseaux et al., 2021).
  5. Breeding harbour seals are surveyed in June and July in a small number of areas. 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 within the Proposed Development marine mammal study area. Therefore, no data was available for haul-out sites considered within this report.

Distribution and occurrence

  1. The telemetry data confirmed harbour seal usage within the Proposed Development marine mammal study area. Of the 46 adult harbour seals tagged in East Scotland between 2001 and 2017, 25 had telemetry track data recorded within the Proposed Development marine mammal study area ( Figure 6.16   Open ▸ ). The telemetry tracks were concentrated to the north-west of the Proposed Development marine mammal study area, with comparatively lower numbers of tracks within the east and south-east of the Proposed Development array area or the Proposed Development export cable corridor. All 25 of these harbour seals also showed connectivity with the Firth of Tay and Eden Estuary SAC. Only two of the 25 harbour seals tagged in the East Scotland MU recorded telemetry data out with the East Scotland MU, with both seals recording telemetry tracks within the Northeast England MU. No harbour seals have been tagged in the Northeast England MU. There were also no harbour seal haul-outs recorded within the Proposed Development marine mammal study area.


Figure 6.16:
Telemetry Tracks for All 25 Harbour Seals that Entered into the Proposed Development Marine Mammal Study Area (Aggregated Data for All Tagged Harbour Seals in the East Scotland MU Between 2001 to 2017)

Figure 6.16: Telemetry Tracks for All 25 Harbour Seals that Entered into the Proposed Development Marine Mammal Study Area (Aggregated Data for All Tagged Harbour Seals in the East Scotland MU Between 2001 to 2017)

Density/abundance

  1. The Proposed Development is located within the East Scotland and North East England MUs. The nearest designated haul out sites for harbour seals in the MU in the vicinity of the Proposed Development are Kinghorn Rocks and Inchmickery and Cow and Calves ( Figure 6.17   Open ▸ ). The main population surveys are carried out when harbour seals are moulting, during the first three weeks of August. The most recent UK wide harbour seal count presented in SCOS (2020) and Sinclair (2022) collates data collected for the count period 2016 to 2019 (Annex B). This produced a total count for the UK of 31,744 seals, which, scaled to account for the proportion of animals at sea at the time of the count, gave an estimated population size of 44,100 (95% CI = 36,000 to 58,700), of which 84.3% are located in Scotland (37,200 animals, 95% CI = 30,400 to 49,600). Overall, the UK harbour seal population has increased since the late 2000s and is close to the 1990s level. However, there are significant differences in the population dynamics between seal MUs. Populations along the east coast of Scotland have generally declined since the early 2000s as within this MU the current population size is at least 40% below the pre-2002 level. Populations in the Tay and Eden SAC are continuing to decline and although continued declines are not evident in the Moray Firth, there is no indication of recovery (SCOS, 2020).
  2. The most recent harbour seal August moult count presented for the East Scotland MU is 343 (2016 to 2019 count period; SCOS, 2020). The population in this MU is mainly concentrated in the Firth of Tay and Eden Estuary SAC and in the Firth of Forth ( Figure 6.17   Open ▸ ). Small groups are also present in the Montrose Basin and at coastal sites in Aberdeenshire. 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 Table 3 in Annex B). Subsequently, the count in 2019 for this SAC was 41, which represents a 95% decrease from the mean counts recorded between 1990 and 2002 (SCOS, 2020). The sporadic counts in the Firth of Forth indicate that the decline is localised within the SAC and may not represent the trends in the overall MU population ( Figure 6.18   Open ▸ ). For example, while this MU has shown a large decline in numbers since the 1996 to 1997 count period, the most recent haul-out count in the 2016 to 2019 period (343) was higher than that in the 2011 to 2015 count period (224) suggesting that the MU population overall may be starting to increase in recent years. Haul-out counts can be scaled by the proportion of seals hauled-out at the time of the count and, using the most recent count, resulted in a total East Scotland MU population size estimate of 476 harbour seals (Sinclair, 2022). The count of harbour seals in the East Scotland MU for harbour seal accounts for approximately 1.1% of the total population of Great Britain.

Figure 6.17:
Harbour seal SACs in the East Scotland and Northeast England MUs and Designated Haul Out Sites in the Vicinity of the Proposed Development

Figure 6.17: Harbour seal SACs in the East Scotland and Northeast England MUs and Designated Haul Out Sites in the Vicinity of the Proposed Development

Figure 6.18:
August Haul Out Counts of Harbour Seals in the East Scotland MU and the Firth of Tay and Eden Estuary SAC. Source: Sinclair (2022)

Figure 6.18:  August Haul Out Counts of Harbour Seals in the East Scotland MU and the Firth of Tay and Eden Estuary SAC. Source: Sinclair (2022)

 

  1. Harbour seal August haul-out counts in the Northeast England MU are low, with annual counts ranging between 38 and 91 ( Figure 6.19   Open ▸ ). Harbour seals in the Tees Estuary have been monitored since 1989 and following a slow increase in numbers from an average of 43 between 2003 and 2008, to an average of 88 in 2015 to 2017, both surveys in 2018 and 2019 produced mean August counts of 76 harbour seals (SCOS, 2020). The most recent haul out count of 79 harbour seals for the 2016 to 2019 count period can be scaled by the proportion of seals hauled-out at the time of the count to resulting in a total Northeast England MU population size estimate of around 110 harbour seals (Sinclair, 2022). The count of harbour seals in the Northeast England MU accounts for approximately 0.25% of the total population of the UK.

Figure 6.19:
Annual August Haul Out Counts of Harbour Seals in the Northeast England MU. Source: Sinclair (2022)

Figure 6.19: Annual August Haul Out Counts of Harbour Seals in the Northeast England MU. Source: Sinclair (2022)

 

  1. Mean harbour seal at sea usage in the vicinity of the Proposed Development is low, with the main area of usage within the Firth of Forth (Carter et al., 2020; Figure 6.20   Open ▸ ). Within the Proposed Development array area the average value (of the mean at sea usage) is estimated at 0.003 (95% Cl = 0.0002 to 0.039) animals per 5 x 5 km grid cell, equating to a density of 0.0001 (95% Cl = 0.000008 to 0.0016) animals per km2. The peak count of harbour seal within grid cells overlapping the Proposed Development array was 0.05 (95% Cl = 0.005 to 0.274) harbour seals, which, assuming uniform density within a grid cell is a density of 0.002 (95% Cl = 0.0002 to 0.01) animals per km2. This peak density aligned with the peak density previously reported by Russell et al. (2017) across the Proposed Development array area. A density of 0.0005 (95% Cl = 0.00003 to 0.04) animals per km2 is representative of the mean densities of harbour seal along the offshore export cable route.

Figure 6.20:
The Distribution and Predicted Number of Harbour Seal in 5 km x 5 km Grid Cells (Mean at Sea Usage) in the Vicinity of the Proposed Development. Source: Carter et al. (2020)

Figure 6.20: The Distribution and Predicted Number of Harbour Seal in 5 km x 5 km Grid Cells (Mean at Sea Usage) in the Vicinity of the Proposed Development. Source: Carter et al. (2020)

  1. Historic boat-based surveys show that harbour seals were seen in low numbers during most months in 2010, with the only exceptions being October and November when no harbour seals were recorded (Sparling, 2012). Harbour seal sightings were lower in 2011 than 2010 and no harbour seals were recorded in February and April to August 2011. Highest encounter rates were in May 2010 and September 2011 at 0.005 individuals per km2. No harbour seals were recorded during the Seagreen boat-based surveys in 2017 (Seagreen, 2018).

Seasonality

  1. A number of seals were recorded during the historic aerial surveys between 2009 and 2010, although majority of them were not identified to species. “All seals” (all seal species sightings grouped together) were distributed across survey area and appeared to be more common offshore in summer (0.0285 sightings per km) than in winter (0.0122 sightings per km) (Grellier and Lacey, 2011).

6.3.2.    Grey Seal

Ecology

  1. Grey seal is the larger of the two pinniped species which occur around the British Isles. Males weigh up to 300 kg and female weight is up to 200 kg. Grey seals can live for over 20 to 30 years, with females tending to live longer than males (SCOS, 2015). Sexual maturity is reached at approximately ten years in males and five years in females (SCOS, 2015), and gestation occurs over ten to eleven months.
  2. Grey seals gather in colonies on land (known as haul-outs) where they breed, rest, moult and engage in social activity (Bonner, 1990). Russell and Lonergan (2012) reported that haul-out events occur also at sea on exposed sandbanks, but their frequency is low, and their duration is on average shorter than those events on land. Breeding occurs between September to December and the annual moult between November to April (Harwood and Wylie, 1987). Female grey seals tend to return to the same breeding site at which they were born in order to give birth. Preferred breeding locations around the UK coast include rocky shores, beaches, caves, sandbanks and small, largely uninhabited islands. Pupping tends to take place between August and November (SCOS, 2018) in the UK. The largest pupping sites are located in the Inner and Outer Hebrides, Orkney, Isle of May, Farne Islands and Donna Nook (JNCC, 2021d). Grey seal give birth to a single, white-coated pup which are weaned over a period of 17 to 23 days (SCOS, 2018), with the pups leaving the breeding site for the sea after approximately one month. Following this, the female comes into oestrus and mating occurs, after which adult grey seal return to sea to forage and build up fat reserves. Just before weaning the pups shed their white natal coat (lanugo) and develop their first adult coat. Moult occurs in stages at the colony with juvenile seal moulting first, followed by adults.
  3. Along the Scottish coast, grey seals exhibit an offshore foraging behaviour (Damseaux et al., 2021). Grey seal have a selective diet, mostly comprised of flatfish and sandeels. A study on the diet of grey seals in Scottish waters found that 50% of prey items were plaice and sole Solea solea and 46% of prey items were sandeels (Damseaux et al., 2021). Hammond et al. (2001) corroborated this finding and highlighted sandeels as an important prey item for grey seals in Scottish waters where they account for approximately 50% of the diet. Gosch (2017) reported that there are significant regional and temporal differences in the diet of grey seal. Seals in shallow waters show a preference for demersal and groundfish species such as cephalopods and flatfish, whilst seals foraging in deeper waters, over sandy substrates, will target pelagic and bentho pelagic species such as blue whiting Micromesistius poutassou and sandeels (Gosch, 2017).
  4. Grey seals tend to forage in the open sea, returning to land regularly to haul out. Foraging trips can be wide-ranging, however, tracking studies have shown that most foraging is likely to occur within 100 km of a haul out site (SCOS, 2018).

Distribution and occurrence

  1. Globally there are three centres of grey seal abundance: one in eastern Canada and the north-east USA, a second around the coast of the UK, especially in Scottish coastal waters, and a third, smaller group in the Baltic Sea. All populations are known to be increasing (SCOS, 2020).
  2. Telemetry data for animals tagged on the east coast of Scotland confirmed grey seal usage of the Proposed Development marine mammal study area (Sinclair, 2022). In total, 46 adult grey seals have been tagged in the East Scotland MU between 1990 and 2013, and a further 23 have been tagged in the Northeast England MU between 1991 and 2008 (Sinclair, 2022). Whilst the focus of this report was on the East Scotland MU and Northeast England MU, all tagged grey seals recorded within these MUs were investigated to determine their origin.
  3. Of the 69 adult grey seals tagged on the east coast of Scotland, 59 of these had tracks within the Proposed Development marine mammal study area: 38 originated from East Scotland MU (corresponding to 82.6% of all adults tagged in this MU), 18 originated from the Northeast England MU (corresponding to 78.3% of all adults tagged in this MU) and three were tagged in the north coast and Orkney MU.
  4. Grey seals tracks were recorded throughout the Proposed Development marine mammal study area, with a higher density of tracks in the north-west of the Proposed Development array area and a lower density of tracks within the eastern parts of the Proposed Development array area and the Proposed Development export cable corridor ( Figure 6.21   Open ▸ ; Sinclair, 2022). The data showed wide ranging behaviour, with individual grey seals tagged in the East Scotland MU moving as far away as the Outer Hebrides and Denmark (green lines in Figure 6.22   Open ▸ ).
  5. The tagging data illustrated connectivity between the Proposed Development marine mammal study area and SACs. A high proportion of tagged individuals were tracked between the Proposed Development marine mammal study area and the Berwickshire and North Northumberland Coast SAC (73%) and Isle of May SAC (41%) (Sinclair, 2022). Additionally, a very small proportion of tagged seals (2 to 3%) had telemetry tracks within the Faray and Holm of Faray SAC, the Humber Estuary SAC), the North Rona SAC and the Monach Islands SAC. Given that these last four SACs are located at further distances from the Proposed Development marine mammal study area, there are lower levels of expected connectivity between these SACs and the Proposed Development.
  6. The movement data was also obtained from the telemetry tags on 38 pup and juveniles, with the majority (~97%) tagged within the East of Scotland MU. It is important to note that pup and juvenile movements may not be representative of the typical movement patterns of adult grey seals, since recently weaned pups are known to disperse widely to haul-out locations far from their birth colony location (Sinclair, 2022). Telemetry track data from the tagged animals showed wide ranging behaviour, with some animals moving into Norwegian and Dutch waters ( Figure 6.22   Open ▸ ). As with the tagged adult grey seals, there was also connectivity demonstrated between the Proposed Development marine mammal study area and SACs for pups/juveniles. Tracks were recorded between the Proposed Development marine mammal study area and the Berwickshire and Northumberland Coast SAC, Isle of May SAC and a small number (5% of tagged animals) within the Humber Estuary SAC.
  7. Historic Seagreen Firth of Forth Round 3 boat-based surveys (2010 – 2011) recorded highest numbers of grey seals over sandy shallow banks such as Scalp Bank, Marr Bank, Wee Bankie and Berwick Bank, which are thought to be important areas for sandeels, a key prey item of grey seal (Sparling, 2012).
  8. During the DAS grey seals were recorded throughout the Proposed Development marine mammal study area (see Figure 3.4 to Figure 3.10 in Annex A). Assuming that all seal species were grey seal (see paragraph 21 in Annex A) the mean encounter rate was 0.011 animals per km (95% CI = 0.014 to 0.007) ( Figure 6.23   Open ▸ ).

Figure 6.21:
Telemetry Tracks for All 59 Adult Grey Seals that Entered into the Proposed Development Marine Mammal Study Area (Coloured by the MU Tagged In)

Figure 6.21: Telemetry Tracks for All 59 Adult Grey Seals that Entered into the Proposed Development Marine Mammal Study Area (Coloured by the MU Tagged In)

Figure 6.22:
Telemetry Tracks for all 38 Pup/Juvenile Grey Seals that Entered into the Proposed Development Marine Mammal Study Area (Coloured by the MU Tagged In)

Figure 6.22: Telemetry Tracks for all 38 Pup/Juvenile Grey Seals that Entered into the Proposed Development Marine Mammal Study Area (Coloured by the MU Tagged In)


Figure 6.23:
Monthly Encounter Rate of Grey Seal Including Seal Species

Figure 6.23: Monthly Encounter Rate of Grey Seal Including Seal Species

 

Density/abundance

  1. The nearest designated haul-out sites for grey seals in the vicinity of the Proposed Development are Kinghorn Rocks and Inchmickery and Cow and Calves (for August survey counts) and Fast Castle, Inchkeith and Craigleith for breeding colonies ( Figure 6.24   Open ▸ ).
  2. The grey seal is considered to have a Favourable Conservation Status in the UK (JNCC, 2018). Since grey seals are counted during the harbour seal August moult surveys, their numbers may be highly variable, such that these surveys provide information on the summer distribution and abundance of grey seals and may not be an accurate reflection of the total population size. The most recent UK wide grey seal haul-out count presented in SCOS (2020) collated data collected between 2016 and 2019. This produced a total count for the UK of 42,765 seals, which, scaled to account for the proportion of animals at sea at the time of the count, gives an estimated population size of approximately 179,000 individuals. The most recent haul-out count for the whole Scotland for the same period reported a total of 25,412 grey seals (Sinclair, 2022) giving an estimated population of approximately 106,300 grey seals in Scotland.
  3. Mean grey seal at sea usage in the vicinity of the Proposed Development is variable, with the hot spots at Berwickshire and Northumberland Coast SAC, Firth of Forth, Tay and Eden Estuary and North of Aberdeen ( Figure 6.25   Open ▸ ; Carter et al., 2020). Carter et al. (2020) used the most up-to-date SMRU telemetry data and habitat preference models to estimate at-sea seal usage and, as agreed through consultation with the stakeholders ( Table 3.1   Open ▸ ), these data are deemed most appropriate for grey seal surface density calculations. Within the Proposed Development array area the average value (of the mean at sea usage) within grid cells was estimated at 30.3 (95% CI = 15.9 to 43.1) animals per 5 x 5 km grid cell, equating to a density of 1.2 (95% Cl = 0.64 to 1.7) animals per km2. This density value is higher than reported by Russell et al. (2017), where grey seal density across the Proposed Development array area was 0.285 animals per km2 and therefore the density of 1.2 animals per km2 will be carried forward as a maximum grey seal density ( Table 7.1   Open ▸ ). Density values within the offshore export cable route are generally lower than those estimated for the Proposed Development array area. There is, however, a single cell overlapping the Proposed Development export cable corridor closest to the shore with an estimated density of 108.87 (95% Cl = 46.5 to 188.6) grey seals per 5 x 5 km grid cell, equating to 4.35 (95% Cl = 1.9 to 7.5) grey seals per km2.


Figure 6.24:
Grey Seal SACs in the East Scotland and North-East England MUs and Designated Haul-Out Sites in the Vicinity of the Proposed Development

Figure 6.24: Grey Seal SACs in the East Scotland and North-East England MUs and Designated Haul-Out Sites in the Vicinity of the Proposed Development

Figure 6.25:
 The Distribution and Predicted Number of Grey Seal in 5 km x 5 km Grid Cells (Mean) in the Vicinity of the Proposed Development. Source: Carter et al. (2020)

Figure 6.25:  The Distribution and Predicted Number of Grey Seal in 5 km x 5 km Grid Cells (Mean) in the Vicinity of the Proposed Development. Source: Carter et al. (2020)

  1. Grey seal in the Firth of Tay and Eden Estuary is counted almost annually (during the harbour seal August moult counts) with highly variable results ranging between the lowest count of 450 in 2009 and the highest count of 2,253 in 2000 (SCOS, 2020). The latest available count for the whole SAC is 686 individuals in 2019. Overall counts for the East Scotland MU have shown an increase in grey seals from 2,328 in the 1996 to 1997 period to 3,683 between 2016 and 2019 (Sinclair, 2022). If scaled to the proportion of the population at sea at the time of the survey, a population estimate within the East Scotland MU is approximately 15,400 grey seals (Sinclair, 2022).
  2. In the Northeast England MU, grey seals are primarily present in the Northumberland area. There has been a significant increase in counts from 603 grey seals in 1996 to1997 to 6,501 between 2016 and 2019 (SCOS, 2020). Comparatively, counts in the Tees which are surveyed annually, have remained low and stable, ranging from 10 in 1995 to 14 in 2019. The total August haul out count of grey seals in the Northeast England MU in the count period 2016 to 2019 was 6,501 grey seals, which accounted for approximately 15% of the grey seals hauled-out in Britain between 2016 and 2019. If scaled to the proportion of the population at sea at the time of the survey, a population estimate within the Northeast England MU is approximately 27,200 grey seals (Sinclair, 2022).
  3. There are four haul out sites within the Proposed Development marine mammal study area where grey seals have been counted during August haul out count surveys (though numbers were low at these sites): Long Craigs (Dunbar), Scart Rock (Dunbar), Black Bull (by Fast Castle, St Abbs) and Fast Castle (St Abbs). These sites are all approximately 6 km to 12 km from the boundary of the Proposed Development export cable corridor.
  4. Grey seals aggregate in the autumn to breed at traditional colonies between August and December. Their distribution during the breeding season is very different to their distribution at other times of the year. Therefore, the main grey seal surveys are conducted late autumn, when females congregate on land to give birth, to estimate the number of pups born at the main breeding colonies around the UK.
  5. There has been a continual increase in the total UK pup production since regular surveys began in the 1960s (SCOS, 2020). There are five grey seal breeding sites in the East Scotland MU, all located within the Firth of Forth region (Craigleith, Fast Castle, Inchcolm, Inchkeith and the Isle of May) ( Figure 6.24   Open ▸ ). Additionally, there is one grey seal breeding site in the Northeast England MU (the Farne Islands). The pup production counts in this area used to be dominated by the Isle of May and the Farne Islands: however, in recent years the pup counts at Fast Castle have significantly increased such that it now has the largest pup production count in the area (SCOS, 2020).
  6. The main Scottish breeding surveys were last flown in 2016 (Inner Hebrides, Outer Hebrides, Orkney) and 2018 (Firth of Forth). The total number of pups estimated to have been born in 2018 in the UK was 68,050 (95% CI = 60,500 – 75,100 pups). Based on this most recent pup count, the adult population size at the start of the 2019 breeding season was estimated to be 149,700 (95% CI = 120,000 – 174,900) (SCOS 2020). For Scotland alone, the pup production was estimated as 55,200 individuals which accounted for 81.1% of the grey seal pups born in the UK (Sinclair, 2022). Pup production estimates were not presented for individual SACs in SCOS reports, however, as advised by NatureScot as a part of the scoping opinion (NatureScot Scoping Opinion for 2020 Berwick Bank (7 October 2020)), the pup production for the Isle of May SAC was predicted based on the Firth of Forth haul-outs and was estimated as 6,894 pups (SCOS, 2020). The pup production count for Berwickshire and North Northumberland Coast SAC was predicted based on the combined estimates from the Firth of Forth (6,894) and the Farne Islands (2,737) accounting for a total of 9,631 pups (SCOS, 2020).
  7. The grey seal population in the North Sea has grown almost constantly since the mid-1990s, and approximately 80% of the pups in this region are born within the following SACs: Isle of May SAC, Berwickshire and North Northumberland coast SAC (which is made up of Fast Castle and the Farne Islands), and the Humber Estuary SAC (includes Donna Nook).
  8. Seasonal density estimates estimated from the Proposed Development aerial digital survey data highlighted that mean monthly densities of grey seal (including seal species) within the Proposed Development marine mammal study area were highest during spring months. Mean monthly density was estimated as 0.043 (95% CI = 0.024 to 0.083) animals per km2. Correcting this for availability bias based on telemetry data on tagged seals in the North Sea (Orsted, 2018; Thompson et al., 1991) gave an absolute mean monthly density of 0.276 (95% CI = 0.154 to 0.532) animals per km2 with a peak mean density during spring months of 0.321 (95% CI = 0.179 to 0.603) ( Table 6.4   Open ▸ ). These densities are comparable with the estimated mean at-sea density of grey seal predicted from the SMRU data (Russell et al., 2017) of 0.285 animals per km2 across the Proposed Development array area, however, are lower than mean value of 1.2 animals per km2 reported by Carter et al. (2020). Therefore, the range of densities carried forward for grey seal in the marine mammal study area was 0.276 to 1.2 animals per km2 ( Table 7.1   Open ▸ ). Corrected mean abundance of grey seal within the Proposed Development marine mammal study area ranged between 938 animals in winter and 1,605 animals in spring months Table 6.4   Open ▸ .

 

Table 6.4:
Grey Seal Plus Seal Species Modelled Absolute Density Estimates by Season for Proposed Development Including LCI and UCI. Abundance Estimates Are Scaled Up to the Proposed Development Plus ~16 km Buffer

Table 6.4: Grey Seal Plus Seal Species Modelled Absolute Density Estimates by Season for Proposed Development Including LCI and UCI. Abundance Estimates Are Scaled Up to the Proposed Development Plus ~16 km Buffer

 

Seasonality

  1. Grey seal sighting rates during historic boat-based surveys (2010 to 2011) were lowest over the autumn and winter. Given that grey seals aggregate in the autumn to breed at traditional colonies between August and December, during these months the number of seals might be expected to be low as a large proportion of the population will be hauled out to breed (Sparling, 2012). Encounter rates of grey seals at sea peaked during June in both years – this is likely to be related to the capital breeding habit of grey seals and possibly indicative of a period of intense foraging where adult seals are at-sea gaining energy reserves prior to the breeding season.
  2. The Seagreen boat-based surveys recorded grey seals on every trip. Numbers of grey seals recorded was highest, 45 animals in early summer (9 and 10 May 2017) and lowest in late summer, 15 animals (15 and 16 August 2017). Mid-summer surveys recorded 22 animals (24 and 25 May 2017), 25 animals (20 and 21 June 2017) and 20 animals (25 and 26 July 2017) (Seagreen, 2018).
  3. During the DAS grey seals were recorded within the Proposed Development array area every month except March 2020 with a sightings peak in April 2020.