9.6.1.1.3 Behaviour


9.6.1.1.3.1 Strong Aversive Response (Fleeing) 102. The fleeing ranges for marine mammals, shown in Table 9.6 to Table 9.9, were obtained following the approach described in Section 9.5 and are based on data from Lucke et al. (2009) for harbour porpoise and Southall et al. (2007) for low and mid-frequency cetaceans and pinnipeds. Assuming a 3,500kJ hammer blow energy, the fleeing response range for East Anglia THREE may be expected to be less than 500m for low-frequency cetaceans, mid-frequency cetaceans and pinnipeds in water and less than about 8km for harbour porpoise. As for the onset of auditory injury range estimates, fleeing response too would be expected to occur at smaller ranges for hammer blow energies less than 3,500kJ as indicated in Table 9.6 to Table 9.9. Southall et al. (2007) criteria for mid-frequency cetaceans applied here (both severity scaling and single pulse response) relate to larger species such as the beluga, killer and sperm whale and it may be that these are less applicable to smaller mid- frequency cetaceans such as the dolphin species. However, more recent work by Finneran et al. (2012), exposing a bottlenose dolphin to a seismic airgun, indicates that this higher level threshold may not be unrealistic and small mid-frequency cetaceans may well be less sensitive to impulsive sounds than suggested by Tougaard et al. (2009), Lucke et al. (2009), Brandt et al. (2011) and Dähne et al. (2013), for example, for the harbour porpoise. For pinnipeds, fleeing and possible avoidance behaviour are taken to occur at the same noise levels as discussed above (Section 9.5). Based on this information, the predicted fleeing response for a pinniped during construction at East Anglia THREE would be expected to be less than around 2.5km (Table 9.9) from the pile for any hammer blow energy considered in the assessment.


9.6.1.1.3.2 Aversive Response (Avoidance of Area) 103. Avoidance information is not provided in the Marine Mammal Noise Exposure Criteria (Southall et al. 2007) for high-frequency cetaceans exposed to multiple pulses. Recent work in Denmark and Germany (Tougaard et al. 2009 and Brandt et al. 2011, Dähne et al. 2013) shows that behavioural disturbance / avoidance may occur over larger distances (around 20km or more) than that implied by the fleeing response. Work by Lucke et al. (2009), who exposed harbour porpoise to a seismic airgun, provides indicative noise levels at which avoidance may occur. For East Anglia THREE, this results in an estimate of disturbance (or possible avoidance) range of between about 37km and 70km for full hammer strike energy at 3,500kJ. The spread in these ranges is due to variations in bathymetry and therefore propagation efficiency. As could be seen in Plate 9.1, for example, there is considerable variation in sound propagation around East Anglia THREE that stems from the changes in


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 41


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