• • 92.
General behavioural response (fish move to bottom of cage) – 168 to 173dB re 1 μPa (McCauley et al. 2000a and 2000b);
Startle response / C-turn reaction – 200dB re 1 μPa (Pearson et al. 1992).
These response levels are only indicative and the level of behavioural disturbance will depend on the context including a number of factors such as the type of fish, its sex, age and condition, as well as other stressors to which the fish is or has been exposed. The response of the fish would be expected to depend on the reasons and drivers for the fish being in the area. Foraging or spawning, for example, may increase the desire for the fish to remain in the area despite the elevated noise level. The use of criteria derived from observed responses in the far-field of a sound source removes the requirement to consider the acoustic particle velocity in the water column, due to the acoustic pressure and acoustic particle velocity components of the field being in phase, i.e., whether the fish responded to the acoustic pressure or particle velocity is irrelevant as long as the absolute level of one or the other is measured at the exposure location.
Table 9.4. Summary of injury criteria for fish. Species
Peak Pressure Level
(dB re 1 μPa) Fish 206 211 (cumulative)
Table 9.5. Summary of behavioural criteria for generic fish species. Species
General behavioural response Startle response / C-turn reaction
SEL (dB re 1 μPa2·s)
Peak Pressure Level (dB re 1 μPa)
168 - 173* 200*
*These levels have been establish from a seismic airgun and should therefore only be applied for impulsive sound source and considered for fish that are sensitive to low-frequency sound (e.g. ~ 500Hz and less).
9.6 Possible Impact of Underwater Noise for East Anglia THREE
9.6.1 Construction Phase 93. Underwater noise from impact piling is known to result in significant peak pressure levels and SEL and will be distinguishable above ambient noise over distances of several tens of km from the source (Thomsen et al. 2006; Nedwell et al. 2007; Bailey et al. 2010). Foundation types which rely on impact piling are considered the worst
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 34
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