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117. The underwater noise modelling results suggest that the startle response or C-turn reaction, which indicates a very strong dislike to the sound, is unlikely to occur at ranges beyond 1km from the pile for 3,500kJ hammer blow energy (Table 9.10 and Table 9.11).


118. As can be seen in Plate 9.10 and Plate 9.11 there is variation in the distances where general behavioural response for fish may be expected around East Anglia THREE, depending on the bearing from the source, which reflects the changes in bathymetry. Favourable sound propagation conditions to the west of East Anglia THREE mean that the impact ranges are generally larger towards the south-west to north-west of East Anglia THREE. In general, the deeper water areas also result in larger impact ranges for behavioural disturbance. Plate 9.12 and Plate 9.13 show the potential noise footprint which may be predicted for fish. This shows the possible spatial extent of the piling noise in terms of fish behavioural disturbance, with no regard for specific temporal construction sequencing across the project (see Section 9.4 for more detail).


119. As with marine mammals the predicted impact ranges modelled include a range of hammer strike energies up to a maximum of piling hammer energy of 3,500kJ. The estimated impact ranges for each of the hammer energies considered are summarised in Table 9.10 and Table 9.11.


120. Despite the numerous windfarm installations currently underway or planned in European waters, very few studies have been undertaken on the behavioural reaction of any marine fauna to marine piling activities. This is particularly the case for fish species. Furthermore, the level and type of response will be dependent on the type of fish, its sex, age and condition and on the reasons and drivers for the fish being in the area (e.g., spawning, migrating). The type of fish and the reason for it being in the area are likely to influence where in the water column the fish is when exposed to the sound. As indicted in Table 9.10 and Table 9.11, this will influence the level of sound to which the fish will be exposed, both in terms of pressure and particle velocity. Fish which are present near the seabed will be exposed to lower sound levels and the range of impact will be less as described in Section 9.4. Most fish will be able to perceive ambient noise and this will likely dictate the lower sound level which they can detect, except for species with particularly poor hearing sensitivity.


121.


It should be noted that no long-term observational studies have been reported in the literature to assess the response of fish populations to marine impact piling and so any fish behaviour impact criteria should strictly only be used for guidance.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 53


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