seismic activity had ceased (Hassel et al. 2004). The results of this study indicate that effects of such noise levels on sandeel are likely to be short term, localised and constrained to behavioural level effects, with no longer term effects likely.
170. Figure 11.56 depicts Sandeel grounds (Jensen et al. 2011), showing a very small overlap with the modelled 168dB contour when compared to other areas available in the Sandeel assessment areas SA1 and SA2. As such, underwater noise on sandeel is considered to be of low magnitude in the context of behavioural responses. Due to the ecological and conservation status of sandeels, they are considered to be of medium sensitivity, with the result that an impact of minor adverse significance is predicted.
Elasmobranchs 171. Elasmobranchs are thought to be sensitive to the particle displacement component of sounds within the range of 20–1000 Hz (Casper and Mann 2006, 2010), although laboratory studies have raised questions over sharks' capability of detecting sounds in the acoustic far field (Casper and Mann 2006).
172. Elasmobranchs have a wide distribution throughout the North Sea and the level of effect-receptor interaction between elasmobranchs and piling noise is expected to be minimal. The magnitude of the effect of noise on behavioural responses of elasmobranchs is low. Their sensitivity to underwater noise is considered to be low, resulting in an impact of minor adverse significance impact.
Diadromous species 173. Diadromous migratory species occur only occasionally in the area of the East Anglia THREE site and its vicinity (see Appendix 11.2, section 11.5.12). Given the distance of the East Anglia THREE site from the coast, it is not expected that diadromous species would be subjected to a noise impact that would result in a behavioural response. In addition, diadromous species are considered to be highly mobile with the ability to escape from impact areas where noise levels are sufficiently high to trigger avoidance reactions. The magnitude of the impact is anticipated to be low.
174. Diadromous migratory species are considered to have low sensitivity to piling noise but considering the high conservation value of these species the sensitivity level has been modified to medium. Taking the above into account, the impact of piling noise on the migration of diadromous species is considered to be of minor adverse significance.
175. Table 11.24 summarises potential behavioural responses as a result of underwater noise during the construction phase.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 11 Fish and Shellfish Page 65
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