piling, it may be required in certain instances to install foundations to full design penetration.
123. For the purposes of this assessment, piling is assumed to occur throughout the first two years of the construction phase, although piling would not be constant throughout this period. The use of soft start and ramp up procedures would reduce the potential for mobile fish receptors to be exposed to instantaneous injury or permanent loss of hearing sensitivity (Permanent Threshold Shift (PTS)).
124. There have been few studies of the effects of anthropogenic noise on the behaviour of fish and shellfish with data lacking on the behavioural effects on fish in close proximity to noise sources. Similarly, there is little information on the long-term effects of exposure to sound on fish behaviour or about cumulative effects.
125. The majority of behavioural experiments have been conducted on captive fish and do not reflect conditions in the natural environment.
126. When assessing noise impacts on fish, species have previously been characterised as either hearing generalists or specialists (Underwater Noise Modelling, Appendix 9.1). In general, hearing generalists were described as fish species having hearing capabilities over relatively narrow frequency ranges from 50Hz or below to 1,000Hz- 1,500Hz, although this varies considerably between species. Hearing specialists were considered to have improved sensitivity over the same range as hearing generalists but also sensitivity to sound at higher frequencies extending above 3,000Hz.
127. These differences in hearing ability were related primarily to physiological differences; hearing specialists have a structure linking the swim bladder and ears, whereas hearing generalists do not usually have this connection (Webb et al. 2008).
128. For the purpose of this assessment, these categorisations may not be strictly relevant as piling operations generate acoustic energy of 100 to 400Hz. Therefore, this higher frequency capability is of little relevance with regards to piling noise. The approach of categorising hearing specialists and hearing generalists is therefore no longer advocated by its originators (Underwater Noise Modelling, Appendix 9.1).
129. Extrapolation of hearing capabilities between different species, and especially those which are taxonomically distant requires cautious interpretation (Hastings and Popper 2005). There is also insufficient evidence in the peer reviewed literature for species specific impact ranges. In light of the above, generic (non-species specific) criteria have been used to model the ranges at which injury and behavioural impacts are expected to occur in fish. The impact criteria are based on those proposed by
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 11 Fish and Shellfish Page 54
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