Sensitivity of the Receptor
  1. The sensitivity of the fish and shellfish IEFs, for both marine and diadromous species, can be found in the construction phase assessment (see paragraph 120 et seq.).
Significance of the effect

Marine Species

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity for most fish and shellfish IEFs is considered to be low to medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
  2. For herring, the magnitude of the impact is deemed to be low and the sensitivity is considered medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
  3. For Nephrops and lobster, the magnitude of the impact is deemed to be low and the sensitivity is considered low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Diadromous Species

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No additional fish and shellfish ecology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.

Injury and/or disturbance to fish and shellfish from underwater noise and vibration

Construction Phase

Magnitude of Impact
  1. The installation of foundations within the Proposed Development fish and shellfish ecology study area may lead to injury and/or disturbance to fish and shellfish species due to underwater noise during pile driving. The maximum design scenario, as outlined in Table 9.15   Open ▸ , considers the greatest effect from underwater noise on fish and shellfish IEFs, considering both the greatest hammer energy. This scenario is represented by the installation of up to 179 piled jacket foundations (1,432 piles) for wind turbines, and up to ten jacket foundations (256 piles) for OSP/Offshore convertor substation platforms, with each pile installed via impact/percussive piling. Two scenarios were modelled with respect to hammer energy: an average maximum hammer energy of 3,000 kJ and an absolute maximum hammer energy of up to 4,000 kJ.
  2. For wind turbines, piling was assumed to take place over a period of on average nine hours per pile (maximum duration of up to ten hours per pile) with up to five piles installed in each 24-hour period. OSP/Offshore convertor substation platform foundations will take place over a period of on average seven hours per pile (maximum duration of up to eight hours per pile) with up to three piles installed in each 24-hour period. A maximum duration of 16,368 hours of piling activity, over a maximum 372-day period, may take place during the construction phase, based on the maximum duration of the piling phase.
  3. UXO clearance (including detonation) also has the capability to cause injury and/or disturbance to fish and shellfish IEFs. Clearance will be completed prior to the construction phase (pre-construction). Until detailed pre-construction surveys are completed within the Proposed Development fish and shellfish ecology study area, the precise number of potential UXO which will need to be cleared is unknown. Drawing on the experience of UXO at other North Sea sites, the maximum number of UXO that may require clearance is up to 14 for the Proposed Development. The maximum design scenario assumes that each of these will be detonated using low order processes, with the assumption that one high order detonation may occur (see Table 9.15   Open ▸ ). Many of these may be left in situ and microsited around. Detonation of UXO would represent a short term (i.e. seconds) increase in underwater noise (i.e. sound pressure levels and particle motion) which will be elevated to levels which may result in injury or behavioural effects on fish and shellfish species (discussed further in paragraph 159 et seq.).
  4. To understand the magnitude of noise emissions from piling and UXO clearance during construction activity, underwater noise modelling has been undertaken considering the key parameters summarised above. Full details of the modelling undertaken are presented in volume 3, appendix 10.1.
  5. Piling activities were modelled for jacket foundations at six locations within the Proposed Development fish and shellfish ecology study area array area taking into account the varying bathymetry and sediment type across the model areas (see volume 3, appendix 10.1). Underwater noise modelling included the use of ‘soft start’ mitigation to reduce the potential for injury effects (as set out in Table 9.20   Open ▸ ). The implications of the modelling for fish and shellfish injury and behaviour are outlined in the following sensitivity section.
  6. All other noise sources including cable installation and foundation drilling are non-percussive and will result in much lower noise levels and therefore much smaller injury ranges (in most cases no injury is predicted) than those predicted for piling operations. For further information on other noise sources see volume 3, appendix 10.1.
  7. The impact is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.
Sensitivity of the Receptor
  1. The following sections apply to both marine fish and shellfish species, and diadromous fish species, with a summary for each of these receptor groups in paragraphs 185 to 196.
  2. Underwater noise can potentially have an adverse impact on fish species ranging from physical injury/mortality to behavioural effects. Recent peer reviewed guidelines have been published by the Acoustical Society of America (ASA) and provide directions and recommendations for setting criteria (including injury and behavioural criteria) for fish. The Sound Exposure Guidelines for Fishes and Sea Turtles (Popper et al., 2014) are considered to be most relevant and best available guidelines for impacts of underwater noise on fish species (see volume 3, appendix 10.1). The Popper et al. (2014) guidelines broadly group fish into the following categories according to the presence or absence of a swim bladder and on the potential for that swim bladder to improve the hearing sensitivity and range of hearing (Popper et al., 2014):
  • Group 1: Fishes lacking swim bladders (e.g. elasmobranchs and flatfish). These species are only sensitive to particle motion, not sound pressure and show sensitivity to only a narrow band of frequencies;
  • Group 2: Fishes with a swim bladder but the swim bladder does not play a role in hearing (e.g. salmonids and some Scombridae). These species are considered to be more sensitive to particle motion than sound pressure and show sensitivity to only a narrow band of frequencies;
  • Group 3: Fishes with swim bladders that are close, but not connected, to the ear (e.g. gadoids and eels). These fishes are sensitive to both particle motion and sound pressure and show a more extended frequency range than Groups 1 and 2, extending to about 500 Hz; and
  • Group 4: Fishes that have special structures mechanically linking the swim bladder to the ear (e.g. clupeids such as herring, sprat and shads). These fishes are sensitive primarily to sound pressure, although they also detect particle motion. These species have a wider frequency range, extending to several kHz and generally show higher sensitivity to sound pressure than fishes in Groups 1, 2 and 3.
    1. Relatively few studies have been conducted on impacts of underwater noise on invertebrates, including crustacean species, and little is known about the effects of anthropogenic underwater noise upon them (Hawkins and Popper, 2016; Morley et al., 2013; Williams et al., 2015). There are therefore no injury criteria that have been developed for shellfish, however, these are expected to be less sensitive than fish species and therefore injury ranges of fish could be considered to be conservative estimates for shellfish species (risk of behavioural effects are discussed further below for shellfish).
    2. An assessment of the potential for injury/mortality and behavioural effects to be experienced by fish and shellfish IEFs with reference to the sensitivity criteria described above is presented in turn below.

Injury

  1. Table 9.21   Open ▸ summarises the fish injury criteria recommended for pile driving based on the Popper et al. (2014) guidelines, noting that dual criteria are adopted in these guidelines to account for the uncertainties associated with effects of underwater noise on fish.

 

Table 9.21:
Criteria for Onset of Injury to Fish due to Impulsive Piling (Popper et al., 2014)

Table 9.21: Criteria for Onset of Injury to Fish due to Impulsive Piling (Popper et al., 2014)

a Relative risk (high, moderate, low) is given for animals at three distances from the source defined in relative terms as near field (N; i.e. 10s of metres), intermediate (I; i.e. 100s of metres), and far field (F; i.e. 1000s of metres); Popper et al. (2014).

 

  1. The full results of the underwater noise modelling are presented in volume 3, appendix 10.1. For the purpose of this assessment, a conversion factor range of 0.5 to 4% was applied as this represents an adequately conservative range for which energy from piling is transferred into sound energy. It should be noted that sensitivity analysis was undertaken on other, more conservative conversion factors, which is presented in volume 3, appendix 10.1. In order to inform this assessment, Table 9.22   Open ▸ and Table 9.23   Open ▸ display the predicted injury ranges associated with the installation of one 5.5 m diameter pile, for peak sound pressure levels (SPLpk) and cumulative sound exposure level (SELcum) respectively. This modelled scenario resulted in the greatest predicted injury ranges and therefore forms the focus of the assessment for injury.
  2. For peak pressure noise levels when piling energy is at its maximum (i.e. 4,000 kJ), mortality and recoverable injury to fish may occur within approximately 138 m – 228 m of the piling activity (lower estimate for Group 1 fish species, higher estimate for Group 4 species). The potential for mortality or mortal injury to fish eggs would also occur at distances of up to 228 m ( Table 9.22   Open ▸ ), with a low to moderate risk of recoverable injury to eggs and larvae within the range of hundreds of metres (see Table 9.21   Open ▸ for qualitative criteria). It should be noted that these ranges are the maximum ranges for the maximum hammer energy, and it is unlikely that injury will occur in this range due to the implementation of soft starts during piling operations, which will allow fish to move away from the areas of highest noise levels, before they reach a level that would cause an injury. The initial injury ranges for soft start initiation will be considerably smaller than those maximum ranges presented in Table 9.22   Open ▸ (i.e. of the order of tens of metres, depending on the fish species considered).
  3. For cumulative SEL, injury ranges were calculated for piling activities undertaken for the maximum energy scenario and for a realistic hammer energy scenario (i.e. average maximum; Table 9.23   Open ▸ ). These ranges indicate that with the implementation of soft start initiation, the mortality and recoverable injury ranges are considerably smaller than those predicted for SPLpk (i.e. mortality thresholds were not exceeded and recoverable injury to maximum ranges of 67 m; see Table 9.23   Open ▸ ). This table also presents ranges of effect for Temporary Threshold Shift (TTS) for all fish groups. As outlined above, TTS is a temporary reduction in hearing sensitivity caused by exposure to intense sound. Normal hearing ability returns following cessation of the noise causing TTS, though the recovery period is variable, during which fish may have decreased fitness due to a reduced ability to communicate, detect predators or prey, and/or assess their environment. Table 9.24   Open ▸ presents the ranges at which TTS in fish may occur as a result of piling for one 5.5 m pile, with TTS predicted to occur to maximum ranges of 4,161 m from piling operations (smaller ranges for basking shark and the realistic maximum hammer energy).
  4. The injury ranges presented indicate that injury may occur out to ranges of tens to a few hundred metres, based on the maximum design scenario. However, in reality, the risk of fish injury will be considerably lower due to the hammer energies being lower than the absolute maximum modelled, as demonstrated by the lower injury ranges associated with initiation and soft starts in Table 9.22   Open ▸ . The expected fleeing behaviour of fish from the area affected when exposed to high levels of noise and the soft start procedure, which will be employed for all piling (see Table 9.20   Open ▸ ), mean that it is likely that fish will have sufficient time to vacate the areas where injury may occur prior to noise levels reaching that level.

 

Table 9.22:
Summary of Peak Pressure Injury Ranges for Fish due to Phase of Impact Piling resulting in Maximum Peak Sound Pressure Level, for both Wind Turbine Foundations and OSP/Offshore Convertor Substation Platform Foundations Based on the Peak Pressure Metric

Table 9.22: Summary of Peak Pressure Injury Ranges for Fish due to Phase of Impact Piling resulting in Maximum Peak Sound Pressure Level, for both Wind Turbine Foundations and OSP/Offshore Convertor Substation Platform Foundations Based on the Peak Pressure Metric

 

Table 9.23:
Injury Ranges for Fish due to Impact Pile Driving for the “Realistic” and “Maximum” Pile Driving for Wind Turbine Jacket Foundations, and for the Piling of the OSP/Offshore Convertor Substation Platform Jackets Based on the Cumulative SEL Metric (N/E Denotes where Thresholds are not Exceeded)

Table 9.23: Injury Ranges for Fish due to Impact Pile Driving for the “Realistic” and “Maximum” Pile Driving for Wind Turbine Jacket Foundations, and for the Piling of the OSP/Offshore Convertor Substation Platform Jackets Based on the Cumulative SEL Metric (N/E Denotes where Thresholds are not Exceeded)

 

  1. Noise modelling was also undertaken for the concurrent piling of wind turbine foundations or wind turbine and OSP/Offshore convertor platform foundations. As outlined in volume 3, appendix 10.1, mortality and recoverable injury ranges were unchanged for the concurrent piling scenario and therefore TTS ranges only are presented in Table 9.24   Open ▸ . This indicates that for concurrent piling, TTS ranges may be increased to up to 7.1 km from the piling location and 5.6 km for realistic hammer energy.

 

Table 9.24:
TTS Injury Ranges for Fish due to Impact Pile Driving at Two Locations Concurrently, for the “Realistic” and “Maximum” Pile Driving for Wind Turbine Jacket Foundations Based on the Cumulative SEL Metric

Table 9.24: TTS Injury Ranges for Fish due to Impact Pile Driving at Two Locations Concurrently, for the “Realistic” and “Maximum” Pile Driving for Wind Turbine Jacket Foundations Based on the Cumulative SEL Metric

 

  1. Underwater noise modelling has also been completed for underwater noise associated with UXO clearance/detonation. Modelling was undertaken for a range of orders of detonation, from a realistic worse case high order detonation to low order detonations (e.g. deflagration and clearance shots) to be used as mitigation to minimise noise levels. Table 9.25   Open ▸ details the injury ranges for fish of all groups in relation to various orders of detonation. The method of low order has been committed to (see Table 9.20   Open ▸ ) and as such will be the dominant method of UXO clearance, although higher order detonations may also occur if low order is not successful or unintentionally as part of the low order process.

 

Table 9.25:
Injury Ranges for all Fish Groups Relating to Varying Orders of Detonation

Table 9.25: Injury Ranges for all Fish Groups Relating to Varying Orders of Detonation

 

  1. Of the key shellfish species of the Proposed Development fish and shellfish ecology study area, decapod crustaceans (e.g. European lobster and crab) are believed to be physiologically resilient to noise as they lack gas filled spaces within their bodies (Popper et al., 2001). To date no lethal effects of underwater noise have been described for edible crab, European lobster or Nephrops, however a number of sub-lethal physiological effects have been reported among Nephrops and related species. In a report by Christian et al. (2003), no significant difference was found between acute effects of seismic airgun exposure (a similar impulsive high amplitude noise source to piling; >189 dB re 1 μPa (peak–peak) @ 1 m) upon adult snow crabs Chionoecetes opilio in comparison with control crabs. Another study investigated whether there was a link between seismic surveys and changes in commercial rock lobster Panulirus cygnus based on rates associated with acute to mid-term mortality over a 26-year period. This found no statistically significant correlative link (Parry and Gason, 2006).
  2. Sub-lethal physiological effects have been identified from impulsive noise sources including bruised hepatopancreas and ovaries in snow crab exposed to seismic survey noise emissions (at unspecified SPLs) (DFO, 2004). Changes in serum biochemistry and hepatopancreatic cells (Payne et al., 2007), increase in respiration in brown shrimp Crangon crangon (Solan et al., 2016) and metabolic rate changes in green shore crab Carcinus maenas have also been identified.
  3. In terms of shellfish eggs and larvae there is no direct evidence to suggest they are at risk of direct harm from high amplitude anthropogenic underwater noise such as piling (Edmonds et al., 2016). Of the few studies that have focussed on the eggs and larvae of shellfish species, evidence of impaired embryonic development and mortality has been found to arise from playback of seismic survey noise among gastropod and bivalve species (De Soto et al., 2013, Nedelec et al., 2014). There is limited information on the effect of impulsive sound upon crustacean eggs, and no research has been conducted on commercially exploited decapod species in the UK. Of the evidence that is available all studies focus on the impact of seismic noise. Preliminary findings show that seismic exposure could be implicated in delayed hatching of snow crab eggs, causing resultant larvae to be smaller than controls (DFO, 2004) and Pearson et al. (1994) found no statistically significant difference between the mortality and development rates of stage II Dungeness crab Metacarcinus magister larvae exposed to single field-based discharges (231 dB re 1 μPa (zero-peak) @ 1 m) from a seismic airgun.
  4. While the evidence described above from species specific studies and primarily laboratory based experiments have shown some effects on shellfish species (although lower level effects compared to fish species), another recent study examined the effects on catch rates of European lobster of a temporary closure of lobster fishing grounds during offshore wind farm construction (including piling) (Roach et al., 2018). Monitoring data at the Westermost Rough Offshore Wind Farm located on the north-east coast of England found that the size and abundance of European lobster increased following temporary closure of the area while construction was undertaken. This study shows that the activities associated with construction of the wind farm, which included piling of foundations for 80 wind turbines, did not impact on the resident European lobster populations and instead allowed some respite from fishing activities for a short period time before reopening following construction (Roach et al., 2018). The results of this study strongly suggest that population level injury effects on shellfish species will not occur due to piling operations.

Behaviour

  1. Behavioural effects in response to construction related underwater noise include a wide variety of responses including startle responses (also known as C-turn responses), strong avoidance behaviour, changes in swimming or schooling behaviour or changes of position in the water column. The Popper et al. (2014) guidelines provide qualitative behavioural criteria for fish from a range of noise sources. These categorise the risks of effects in relative terms as “high”, “moderate” or “low” at three distances from the source: “near” (i.e. tens of metres), “intermediate” (i.e. hundreds of metres) or “far” (i.e. thousands of metres). The behavioural criteria for piling operations are summarised in Table 9.26   Open ▸ for the four fish groupings.

 

Table 9.26:
Potential Risk for the Onset of Behavioural Effects in Fish from Piling (Popper et al., 2014)a

Table 9.26: Potential Risk for the Onset of Behavioural Effects in Fish from Piling (Popper et al., 2014)a

a Note: Relative risk (high, moderate, low) is given for animals at three distances from the source defined in relative terms as near field (N; i.e. 10s of metres), intermediate (I; i.e. 100s of metres), and far field (F; i.e. 1000s of metres); Popper et al. (2014).

 

  1. Group 1 Fish (e.g. flatfish and elasmobranchs), Group 2 Fish (e.g. salmonids) and shellfish are less sensitive to sound pressure, with these species detecting sound in the environment through particle motion. However, sensitivity to particle motion in fish is also more likely to be important for behavioural responses rather than injury (Hawkins, 2009; Mueller-Blenkle et al., 2010; Hawkins et al., 2014a). Group 3 (including gadoids such as cod and whiting) and Group 4 fish (sprat) are more sensitive to the sound pressure component of underwater noise and, as indicated in Table 9.26   Open ▸ the risk of behavioural effects in the intermediate and far fields are therefore greater for these species.
  2. A number of studies have examined the behavioural effects of the sound pressure component of impulsive noise (including piling operations and seismic airgun surveys) on fish species. Mueller-Blenkle et al. (2010) measured behavioural responses of cod and sole to sounds representative of those produced during marine piling, with considerable variation across subjects (i.e. depending on the age, sex, condition etc. of the fish, as well as the possible effects of confinement in cages on the overall stress levels in the fish). This study concluded that it was not possible to find an obvious relationship between the level of exposure and the extent of the behavioural response, although an observable behavioural response was reported at 140 dB to 161 dB re 1 μPa SPLpk for cod and 144 dB to 156 dB re 1 μPa SPLpk for sole. However, these thresholds should not be interpreted as the level at which an avoidance reaction will be elicited, as the study was not able to show this.
  3. A study by Pearson et al. (1992) on the effects of geophysical survey noise on caged rockfish Sebastes spp. observed a startle or “C-turn response” at peak pressure levels beginning around 200 dB re 1 μPa, although this was less common with the larger fish. Studies by Curtin University in Australia for the oil and gas industry by McCauley et al. (2000) exposed various fish species in large cages to seismic airgun noise and assessed behaviour, physiological and pathological changes. The study made the following observations:
  • a general fish behavioural response to move to the bottom of the cage during periods of high level exposure (greater than RMS levels of around 156 dB to 161 dB re 1 μPa; approximately equivalent to SPLpk levels of around 168 dB to 173 dB re 1 μPa);
  • a greater startle response by small fish to the above levels;
  • a return to normal behavioural patterns some 14 to 30 minutes after airgun operations ceased;
  • no significant physiological stress increases attributed to air gun exposure; and
  • some preliminary evidence of damage to the hair cells when exposed to the highest levels, although it was determined that such damage would only likely occur at short range from the source.
    1. The authors did point out that any potential seismic effects on fish may not necessarily translate to population scale effect or disruption to fisheries and McCauley et al. (2000) show that caged fish experiments can lead to variable results. While these studies are informative to some degree, these, and other similar studies, do not provide an evidence base that is sufficiently robust to propose quantitative criteria for behavioural effects (Hawkins and Popper, 2016; Popper et al., 2014) and as such the qualitative criteria outlined in Table 9.26   Open ▸ are proposed.
    2. For the purposes of the underwater noise modelling (volume 3, appendix 10.1), an un-weighted sound pressure level of 150 dB re 1 μPa (RMS) was used as the criterion for indicating the extent of behavioural effects due to impulsive piling based on the Washington State Department of Transport Biological Assessment Preparation for Transport Projects Advanced Training Manual (WSDOT, 2011). At sound pressure levels in excess of 150 dB re 1 μPa (RMS) temporary behavioural changes, such as elicitation of a startle response, disruption of feeding, or avoidance of an area may be expected to occur. It is important to note that this threshold is for onset of potential effects, and not necessarily an ‘adverse effect’ threshold and should be considered alongside other information (including those studies outlined above) in addition to the qualitative criteria set out by Popper et al. (2014) in Table 9.26   Open ▸ . Using this criterion, site specific modelling indicated that behavioural responses may occur to ranges of approximately 17 km for single pile driving and 23 km for concurrent piling (volume 3, appendix 10.1).
    3. Initial outputs of post construction monitoring at the Beatrice Offshore Wind Farm (BOWL, 2021a) concluded that for sandeel there was no evidence of adverse effects on sandeel populations between pre and post construction levels over a six year period (as described in paragraph 80). Cod spawning was also monitored at the same wind farm site (BOWL, 2021b) and similarly, it was concluded that there was no change in the presence of cod spawning between pre and post construction (although spawning intensity was found to be low across both surveys). From these studies, it can be inferred that noise impacts associated with installation of an offshore wind development are temporary and that fish communities (specifically cod and sandeel in this case) show a high degree of recoverability following construction.
    4. As set out in previous sections, information on the impact of underwater noise on marine invertebrates is scarce, and no attempt has been made to set exposure criteria (Hawkins et al., 2014b). Studies on marine invertebrates have shown their sensitivity to substrate borne vibration (Roberts et al., 2016). Aquatic decapod crustaceans are equipped with a number of receptor types potentially capable of responding to the particle motion component of underwater noise (e.g. the vibration of the water molecules which results in the pressure wave) and ground borne vibration (Popper et al., 2001). It is generally their hairs which provide the sensitivity, although these animals also have other sensor systems which could be capable of detecting vibration. It has also been reported that sound wave signature of piling noise can travel considerable distances through sediments (Hawkins and Popper, 2016), with implications for demersal and sediment dwelling fish (e.g. sandeel) and shellfish (e.g. Nephrops) in close proximity to piling operations. Sandeel may be particularly affected by vibration through the seabed during winter hibernation when they remain buried in sandy sediments.
    5. Nephrops have been found to bury less deeply, flush their burrows less regularly and are considerably less active when exposed to impulsive anthropogenic noise (Solan et al., 2016). Nephrops also showed reduced movement and burrowing behaviour in response to simulative shipping and construction noise, however, simulated shipping noise had no effect on the physiology of Nephrops (Solan et al., 2016). Another study on brown shrimp Crangon crangon revealed elevated SPL are implicated in increased incidences of cannibalism and significantly delayed growth (Lagardère and Spérandio, 1981). Simulated shipping noise has been demonstrated to cause some individuals of common shore crab to cease feeding (Wale et al., 2013). The mud crab Scylla paramamosain and European spiny lobsters Palinurus elephas have been reported to have aspects of life history disrupted by anthropogenic noise (e.g. movement and anti-predation behaviour). In contrast to Nephrops, increased movement has been seen in these species in response to simulated shipping noise and offshore activities (Filiciotto et al., 2016; Zhou et al., 2016). Such findings have implications with regard to species fitness, stress and compensatory foraging requirements, along with increased exposure to predators.
    6. However as set out above, monitoring of European lobster catch rates at the Westermost Rough Offshore Wind Farm indicated that population level effects on shellfish species did not occur (Roach et al., 2018). While there may be some residual uncertainty with regard to behavioural effects while piling operations are ongoing, the evidence suggests that long term effects will not occur, and any effects will be reversible.
    7. Scott et al. (2020) provides the most recent review of the existing published literature on the influence of anthropogenic noise and vibration and on crustaceans. The review concluded that some literature sources identified behavioural and physiology effects on crustaceans from anthropogenic noise, however, there were several that showed no effect. The paper notes that to date no effect or influence of noise or vibrations has been reported on mortality rates or fisheries catch rates or yields. In addition, no studies have indicated a direct effect of anthropogenic noise on mortality, immediate or delayed (Scott et al., 2020).

Summary – Marine Species

  1. Injury and/or mortality for all fish species is to be expected for individuals within very close proximity to piling operations, shellfish species injury is expected to be similar however there is some evidence injury may occur at smaller ranges as they may be less sensitive to noise impacts. However, this is unlikely to result in significant mortality due to soft start procedures allowing individuals in close proximity to flee the area prior to maximum hammer energy levels which may cause injury to greater ranges.
  2. In contrast, behavioural effects are expected over much larger ranges, as discussed above. To illustrate this, Figure 9.6   Open ▸ to Figure 9.9   Open ▸ show the modelled underwater noise levels for SPLpk based on the results from volume 3 appendix 10.1, relative to key fish spawning habitats in the vicinity of the Proposed Development fish and shellfish ecology study area. Figure 9.6   Open ▸ and Figure 9.7   Open ▸ show noise contours for two hammer energies (i.e. the maximum 4,000 kJ hammer energy and the average maximum hammer energy of 3,000 kJ, respectively) at the south-west location and Figure 9.8   Open ▸ and Figure 9.9   Open ▸ show the same for the northern piling location. The north and south-west piling locations were chosen as locations which were closest to the most sensitive habitats/areas: the northern location due to its proximity to herring spawning grounds to the north; the south-west as it is closest to the coastline and most likely to cause barrier effects to diadromous species at that location.
  3. Noting that there are no published or agreed thresholds for behavioural effects on fish from piling operations, these figures suggest that behavioural responses will extend over ranges of 10 km to 20 km; for example, assuming avoidance occurs at levels in excess of 160 dB re 1 μPa SPLpk, which is a lower threshold than the levels at which behavioural effects in fish were detected (including McCauley et al., 2000). These results broadly align with qualitative thresholds for behavioural effects on fish as set out in Table 9.26   Open ▸ , with moderate risk of behavioural effects in the range of hundreds of metres to thousands of metres from the piling activity, depending on the species. This is also in line with criterion used in site specific modelling, which predicted behavioural effects to approximately 17 km to 23 km, based on a threshold of 150 dB re 1 μPa (RMS) (see paragraph 179).
  4. With respect to marine species, the key habitats for these species are spawning and nursery habitats, as set out volume 3, appendix 9.1. Although spawning and nursery habitats are present within the Proposed Development fish and shellfish ecology study area (see Table 9.11   Open ▸ ) and the ZoI of underwater noise from piling, these habitats extend over a very wide area across the Proposed Development northern North Sea fish and shellfish ecology study area. The relative proportion of these habitats affected by piling operations at any one time will therefore be small in the context of the wider habitat available. Further, as outlined above, piling operations will be temporary and intermittent throughout the construction phase of the Proposed Development.
  5. Herring are known to be particularly sensitive to underwater noise and have specific habitat requirements for spawning (see section 9.7 and volume 3, appendix 9.1) which makes them particularly vulnerable to impacts associated with construction related underwater noise. The core herring spawning grounds in the ZoI of the Proposed Development sit to the north of the Proposed Development fish and shellfish ecology study area (see volume 3, appendix 9.1). At maximum hammer energy (4,000 kJ) for the north piling location (closest to mapped herring core spawning grounds), there is minimal overlap of the noise contours into the spawning area (see Figure 9.8   Open ▸ ). Where there is overlap with mapped noise contours, these are at the lower range of noise level (e.g. 130-140 dB re 1 μPa SPLpk) which is considerably lower than levels expected to cause any behavioural effects, as previously discussed.
  6. Other species with spawning grounds in the vicinity of the Proposed Development fish and shellfish ecology study area (e.g. sandeel, cod and sprat) have a greater level of overlap with higher noise levels exist within the spawning areas. However, the area of overlap is small in comparison to the extensive nature of the spawning habitats around the Scottish and UK coast. Further, as discussed in paragraph 80, initial outputs of monitoring from the Beatrice Offshore Wind Farm indicate that following cessation of construction operations (including piling) that both cod and sandeel have recovered into any areas potentially affected by construction related underwater noise.
  7. Most marine fish IEFs species in the Proposed Development fish and shellfish ecology study area are deemed to be of low vulnerability, high recoverability and local to national importance. The sensitivity of the receptor is therefore, considered to be low.
  8. Herring, sprat, cod and sandeel are deemed to be of medium vulnerability, high recoverability and regional to national importance. The sensitivity of the receptor is therefore, considered to be medium.
  9. European lobster, Nephrops and edible crab are deemed to be of low vulnerability, high recoverability and regional importance. The sensitivity of the receptor is therefore, considered to be low.

Summary – Diadromous Species

  1. As with marine species, diadromous fish species within close proximity to piling operations may experience injury or mortality. However, the nature of diadromous fish species being highly mobile and tending to only utilise the environment within the Proposed Development fish and shellfish ecology study area to pass through during migration, it is unlikely to result in significant mortality of diadromous species. The use of soft start piling procedures (see Table 9.20   Open ▸ ), allowing individuals in close proximity to piling to flee the ensonified area, further reduces the likelihood of injury and mortality on diadromous species.
  2. Diadromous fish species may experience behavioural effects in response to piling noise, including a startle response, disruption of feeding, or avoidance of an area. As discussed in preceding sections, these would be expected to occur at ranges of 10 km to 20 km, depending on the species and their relative sensitivities to underwater noise (i.e. in order of lowest to highest sensitivities: lamprey species, Atlantic salmon and sea trout, European eel and shad species). Research from Harding et al. (2016) failed to produce physiological or behavioural responses in Atlantic salmon when subjected to noise similar to piling. However, the noise levels tested were estimated at <160 dB re 1 µPa RMS, below the level at which injury or behavioural disturbance would be expected for Atlantic salmon. Due to the distance between the Proposed Development array area and the coast, these behavioural impacts are unlikely to cause barrier effects between the Proposed Development fish and shellfish ecology study area and the migration routes of diadromous species along the east coast of Scotland, due to the relatively small area around piling events where noise levels are high enough to cause behavioural responses (as demonstrated in Figure 9.6   Open ▸ to Figure 9.9   Open ▸ ). This is the case for both downstream migration of smolts and upstream migration of adults. The low risk of effects on migration of diadromous fish species extends to the freshwater pearl mussel, which is included in the diadromous species section, as part of its life stage is reliant on diadromous fish species including Atlantic salmon and sea trout.
  3. Diadromous fish species IEFs in the Proposed Development fish and shellfish ecology study area are deemed to be of low vulnerability, high recoverability and national to international importance. The sensitivity of the receptor is therefore, considered to be low.

Figure 9.6:
Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Southwest Piling Location at 4,000 kJ Hammer Energy

Figure 9.6:  Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Southwest Piling Location at 4,000 kJ Hammer Energy

 

Figure 9.7:
Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Southwest Piling Location at 3,000 kJ Hammer Energy

Figure 9.7:  Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Southwest Piling Location at 3,000 kJ Hammer Energy

 

Figure 9.8:
Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Northern Piling Location at 4,000 kJ Hammer Energy

Figure 9.8: Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Northern Piling Location at 4,000 kJ Hammer Energy

 

Figure 9.9:
Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Northern Piling Location at 3,000 kJ Hammer Energy

Figure 9.9:  Spawning Habitats for Herring, Sandeel, Sprat and Plaice with Underwater Noise Contours (Unweighted SPLpk) Associated with the Northern Piling Location at 3,000 kJ Hammer Energy

Significance of the Effect

Marine Species

  1. For most fish and shellfish IEF species, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
  2. For herring, sprat, cod and sandeel, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
  3. For European lobster, Nephrops and edible crab the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Diadromous Species

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
  2. Similarly, for freshwater pearl mussel, as migration of Atlantic salmon and sea trout will not be significantly affected, effects on freshwater pearl mussel will be of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No additional fish and shellfish ecology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.

Long-term subtidal habitat loss

  1. Long-term subtidal habitat loss within the Proposed Development fish and shellfish ecology study area will occur during construction (i.e. through placement of infrastructure) although effects will extend throughout the operation and maintenance phase ( Table 9.15   Open ▸ ). Long-term habitat loss will occur directly under all wind turbine and OSP/Offshore convertor substation platform foundation structures (suction caisson and piled jacket foundations respectively), associated scour protection and cable protection (including at cable crossings) where this is required. The magnitude has been considered for both construction and operation and maintenance phases combined as the structures will be placed during construction and will be in place during the operation and maintenance phase. This impact also considers the habitat loss occurring during the decommissioning phase based on the maximum design scenario that scour and cable protection may be left in situ following decommissioning.

Construction and Operation and Maintenance Phase

Magnitude of Impact
  1. The presence of infrastructure within the Proposed Development fish and shellfish ecology study area will result in long term habitat loss. The maximum design scenario is for up to 7,798,856 m2 of long term habitat loss due to the installation of foundations and associated scour protection and cable protection associated with array, OSP/Offshore convertor substation platform interconnector, and offshore export cables. Cable protection will also be required for up to 78 cable crossings for the inter-array and OSP/Offshore convertor substation platform interconnector cables and 16 crossings for the offshore export cable. This equates to a small proportion (0.7%) of the Proposed Development fish and shellfish ecology study area.
  2. The long term loss of subtidal habitat involves a change of sediment composition in affected areas (e.g. surrounding foundations and along sections of the Proposed Development array and offshore export cables) from soft sediment habitats (sands, gravels and muds) to hard substrates (foundations, cable protection and scour protection). These areas of habitat loss will be discrete, either in the immediate vicinity of foundations (i.e. foundations and scour protection), or for cable protection these will be relatively small isolated stretches of cable within large areas of sediment which characterise the baseline environment (i.e. soft sediments). This translates into the loss of one type of habitat and the increase of a new habitat. The implications of this are discussed in the sensitivity section (paragraph 207 et seq.) and the potential colonisation of these new substrates is presented and discussed in later assessments of effects (paragraph 259 et seq.). Long-term subtidal habitat loss impacts will occur during the construction phase and will be continuous throughout the 35-year operation and maintenance phase.
  3. The impact is predicted to be of local spatial extent (i.e. affecting only a very small proportion of the Proposed Development particularly in the context of the habitats in the wider area), long term duration, continuous and not reversible during the operation and maintenance phase. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.
Sensitivity of the Receptor

Marine Species

  1. Fish and shellfish species that are reliant upon the presence of suitable sediment/habitat for their survival are considered to be more vulnerable to change depending on the availability of habitat within the wider geographical region. The seabed habitats removed by the installation of infrastructure will reduce the amount of suitable habitat and available food resource for fish and shellfish species and communities associated with the baseline substrates/sediments however this area represents a low percentage compared with the area of habitats located within the Proposed Development northern North Sea fish and shellfish ecology study area.
  2. As confirmed by site specific surveys, the Proposed Development fish and shellfish ecology study area coincides with fish spawning and nursery habitats including plaice, lemon sole, herring, sprat, whiting, cod, haddock, sandeel, mackerel, sprat, Nephrops and elasmobranchs (Coull et al., 1998; Ellis et al., 2012; Aires et al., 2014; see Table 9.11   Open ▸ and volume 3, appendix 9.1). The fish species most vulnerable to habitat loss include sandeel which are demersal spawning species (i.e. eggs are laid on the seabed), as these have specific habitat requirements for spawning (i.e. sandy sediments). This is as identified by the FeAST tool as the pressure ‘Physical change (to another seabed type)’ which has identified that sandeel have high sensitivity to this impact (Wright et al., 2000). As well as laying demersal eggs, sandeel also have specific habitat requirements throughout their juvenile and adult life history and loss of this specific type of habitat could represent an impact on this species. However, monitoring at Horns Rev I, located off the Danish coast, has indicated that the presence of operation wind farm structures has not led to significant adverse effects on sandeel populations in the long term (van Deurs et al., 2012; Stenberg et al., 2011). Initial results of a pre to post construction monitoring study have reported that in some areas of the Beatrice Offshore Wind Farm there was an increase in sandeel abundance (BOWL, 2021a). The findings of a single monitoring study are not able to categorically confirm the conclusion that offshore wind developments are beneficial to sandeel populations; however, it does provide additional evidence that there is no adverse effect on sandeel populations.
  3. The Proposed Development fish and shellfish ecology study area also coincides with high intensity sandeel spawning habitat as confirmed by site-specific surveys (see volume 3, appendix 9.1). The presence of infrastructure will result in direct impacts on this habitat, though as detailed above the proportion of habitat affected within the Proposed Development fish and shellfish ecology study area is small and this area is smaller still in the context of the known sandeel habitats (including spawning and nursery habitats) and the potential sandeel habitats in the Proposed Development northern North Sea fish and shellfish ecology study area (volume 3, appendix 9.1).
  4. Monitoring at Belgian offshore wind farms has reported that fish assemblages undergo no drastic changes due to the presence of offshore wind farms (Degraer et al., 2020). They reported slight, but significant increases in the density of some common soft sediment-associated fish species (common dragonet Callionymus lyra, solenette Buglossidium luteum, lesser weever Echiichthys vipera and plaice) within the offshore wind farm (Degraer et al., 2020). There was also some evidence of increases in numbers of species associated with hard substrates, including crustaceans (including edible crab), sea bass and common squid (potentially an indication that foundations were being used for egg deposition; Degraer et al., 2020). The author noted that these effects were site specific and therefore may not necessarily be extrapolated to other offshore wind farms, although this does indicate the presence of offshore wind farm infrastructure does not lead to adverse, population wide effects.
  5. The Proposed Development fish and shellfish ecology study area is located in the vicinity of known Nephrops spawning habitat, although site specific surveys (including sediment sampling, trawls and seabed imagery) showed that Nephrops habitat was only present along the Proposed Development export cable corridor. Long term habitat loss is predicted to affect a small proportion of this habitat, which will be limited to along the Proposed Development export cable corridor (i.e. array infrastructure is unlikely to affect Nephrops spawning habitat). Lobster spawning and nursery habitats have the potential to occur within the Proposed Development fish and shellfish ecology study area. The proportion of lobster spawning and overwintering habitats affected is, however, likely to be small in the context of the available habitats in this part of the Proposed Development fish and shellfish ecology study area and the wider Proposed Development northern North Sea fish and shellfish ecology study area.
  6. Most fish and shellfish ecology IEFs in the Proposed Development fish and shellfish ecology study area are deemed to be of low vulnerability, high recoverability and local to national importance. The sensitivity of the receptor is therefore, considered to be low.
  7. European lobster and Nephrops are deemed to be of high vulnerability, medium to high recoverability and of regional importance. The sensitivity of these fish and shellfish IEFs is therefore considered to be medium.
  8. Sandeel are deemed to be of high vulnerability, high recoverability and of national importance. The sensitivity of these fish and shellfish receptor is therefore considered to be medium.
  9. Herring are deemed to be of high vulnerability, medium recoverability and of regional importance. However, the sensitivity of herring to this impact is considered to be low, due to the limited suitable spawning sediments overlapping with the Proposed Development fish and shellfish ecology study area and the core herring spawning ground being located well outside the Proposed Development fish and shellfish ecology study area.

Diadromous Species

  1. Diadromous fish species are highly mobile and therefore are generally able to avoid areas subject to long term subtidal habitat loss. Diadromous species that are likely to interact with the Proposed Development fish and shellfish ecology study area are only likely to do so by passing through the area during migrations to and from rivers located on the east coast of Scotland (e.g. those designated sites with diadromous fish species listed as qualifying features; see Table 9.12   Open ▸ and volume 3, appendix 9.1). The habitats within the Proposed Development fish and shellfish ecology study area are not expected to be particularly important for diadromous fish species and therefore habitat loss during the construction and operation and maintenance phase of the Proposed Development is unlikely to cause any direct impact to diadromous fish species and would not affect migration to and from rivers.
  2. Indirect impacts on diadromous fish species may occur due to impacts on prey species, for example larger fish species for sea lamprey and sandeel for sea trout. As outlined previously for marine species, the majority of large fish species would be able to avoid habitat loss effects due to their greater mobility but would recover into the areas affected following cessation of construction. Sandeel (and other less mobile prey species) would be affected by long term subtidal habitat loss, although recovery of this species is expected to occur quickly as the sediments recover following installation of infrastructure and adults recolonise and also via larval recolonisation of the sandy sediments which dominate the Proposed Development fish and shellfish ecology study area. These sediments are known to recover quickly following cable installation (RPS, 2019). Impacts on diadromous species associated with the creation of new hard substrates are presented and discussed in later assessments of effects (see paragraph 259 et seq.).
  3. With reference to the criteria in Table 9.13   Open ▸ and as set out in Table 9.14   Open ▸ , diadromous fish species are deemed to be of low vulnerability, high recoverability and national to international importance. The sensitivity of the receptor is therefore, considered to be low.
Significance of the Effect

Marine Species

  1. For most fish and shellfish IEF species, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
  2. For European lobster and Nephrops, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
  3. For sandeel, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Diadromous Species

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No additional fish and shellfish ecology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.