252. As agreed during consultation with Natural England (Table 12.1) EPS other than harbour porpoise are not considered in the assessment. However, in the interest of ensuring that an injury offence should not be caused to any EPS which could be an occasional visitor to the East Anglia Zone, results of the assessment of PTS onset ranges for low and mid frequency cetaceans (using the Southall et al. 2007 criteria, see Appendix 9.1) will also be summarised and discussed.
Table 12.13
Species or species group
Harbour porpoise
Impact
Summary of criteria used in the assessment Criteria
Instantaneous injury (PTS onset)
Fleeing response (TTS onset)
Pinnipeds (in water)
Instantaneous injury (PTS onset)
Fleeing response (TTS)
12.6.1.1.1 Sensitivity
12.6.1.1.1.1 Lethal and physical injury effects 253. There is a lack of data which has prevented the establishment of explicit exposure criteria and a mechanism for this type of effect in marine mammals. However, in this assessment all species of marine mammal are considered to have high sensitivity to noise above thresholds that can cause instantaneous physical injury or death. Marine mammals are considered to have limited capacity to avoid such effects, and unable to recover from the effects.
12.6.1.1.1.2 Auditory injury (PTS onset) 254. All species of cetacean rely on sonar for navigation, finding prey and communication; they are therefore highly sensitive to permanent hearing damage (Southall et al. 2007). However, when considering the impact that any auditory injury has on an individual the frequency range over which the auditory injury occurs must be considered. PTS or TTS would normally only be expected in the critical hearing bands in and around the critical band of the fatiguing sound (e.g. Kastelein et al. 2012). Auditory injury resulting from sound sources like piling (where most of the energy occurs at lower frequencies) is unlikely to negatively affect the ability of high- frequency cetaceans to communicate or echo-locate. As such, sensitivity to PTS from pile driving noise is assessed as medium for harbour porpoise.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 69
Peak Pressure Level (dB re 1 μPa) 200
194
Possible avoidance of area 168 218
212 SEL (dB re 1 μPa2·s) 179 (single strike) 164 145 186 (Mpw weighted) 171 (Mpw weighted)
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