11.6.1.3.1 Instantaneous Injury (mortality, physical injury and auditory injury) 133. As previously stated, there is limited species specific research into instantaneous injury caused by anthropogenic noise. Furthermore, the noise modelling undertaken for the East Anglia THREE project only differentiates between demersal and pelagic species. The following assessment of the risks of instantaneous injury categorises life stages / species in terms of their mobility.
Mobile Life Stages/ Species 134. Teleost and elasmobranch adults and juveniles are for the purposes of this assessment considered as mobile.
135. The scenarios modelled are based on the assumption of two piling vessels working simultaneously within the East Anglia THREE site. The resultant area affected by noise levels that is likely to cause mortality, physical and auditory injury in both demersal and pelagic fish (SPL>206 dB re 1 μPa), is restricted within a radius of less than 250m of the piling event (Table 11.21 and Table 11.22), equivalent to an impact area less than 0.4km2.
136. As shown in Table 11.21 and Table 11.22, instantaneous injury is expected to occur within 250m of the monopile when using a 3,500kJ hammer energy for both demersal and pelagic species. Cumulative exposure could increase this range, although it should be emphasised that the implementation of soft-start procedures would result in many fish being displaced from the area of effect before noise levels reach the levels predicted for injury and mortality.
137. Taking the extent of the area where noise-related death or injury from piling noise may potentially occur, in addition to the short term and intermittent nature of piling activity, the magnitude of this effect is judged to be negligible as the death or injury of individuals has little potential to create impacts on the size and structure of the stocks of species in the North Sea.
138. The sensitivity of mobile adult and juvenile fish is taken to be low, since they are expected to vacate the area in which the impact could occur with the onset of ‘soft start’ piling. With respect to instantaneous injury due to piling noise, the impact is therefore, assessed to be of negligible significance.
Early Life Stages and Species of Limited Mobility
Early Life stages 139. Early life stages such as larvae would not be able to flee the vicinity of the foundations during piling, however prolonged exposure could be reduced by any drift of larvae due to water currents which may reduce the risk of mortality.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 11 Fish and Shellfish Page 58
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