162. There is the possibility of low level interaction with adults migrating through the East Anglia Zone from feeding grounds in the North Sea to the Downs sub stock main spawning grounds in the Eastern Channel.
163.
ICES (2013) also advises that the North Sea herring stock is currently at full reproductive capacity and it is harvested sustainably with increases of over 95 per cent in the Total Allowable Catch (TAC) for 2012.
164. Any temporary noise effects resulting from piling are therefore not expected to contribute to changes in spawning activity or an increase in mortality that would be detrimental to the Downs sub-population or to the North Sea herring stock as a whole and therefore the magnitude is expected to be low.
165. As spawning activity is highly variable year on year, driven largely by environmental variables (Hufnagl and Peck 2011), and as herring are a highly mobile species any avoidance of the noise impact area during piling is not expected to result in exclusion of individuals from the wider available spawning locations and so a low sensitivity has been assumed. This is further supported by the fact that herring have been reported to relocate to alternative spawning locations between generations (Schmidt et al. 2009).
166. In view of the above, an impact of minor adverse significance is expected to occur.
Sprat 167. With respect to potential impacts on spawning aggregations, sprat utilise coastal and offshore waters during spawning and release their eggs into the water column (Whitehead1986). As a result spawning grounds are widespread around the North Sea and not limited to areas with specific characteristics (Figure 11.60). The magnitude of any effect is considered to be low with a receptor sensitivity equivalent to that of herring i.e. low. The predicted significance of the impact of piling noise causing behavioural effects in sprat is therefore assessed as being of minor adverse significance.
Sandeels 168. Monitoring of lesser sandeels during seismic surveys showed some behavioural reactions to source levels equivalent to 210 dB at 1 mPa (Hassel et al. 2004). After the seismic shooting had ceased however, normal behaviour resumed (Hassel et al. 2004).
169. As no increase in mortality or injurious effects were observed in treatment groups (exposed to seismic shooting) over control groups (not exposed to seismic activity), and no reduction in sandeel abundance in grab surveys was observed after the
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 11 Fish and Shellfish Page 64
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