12.5.2.2.3 Site specific surveys
148. As described for grey seal previously, aerial surveys conducted for the East Anglia Zone, did not record any observations of seals (East Anglia Offshore Wind 2012c) neither did aerial surveys at the East Anglia ONE site. However, during boat based surveys, three harbour seal were recorded, suggesting that there is low usage of the East Anglia ONE site (East Anglia Offshore Wind 2012b).
149. As described for grey seal, observations made during aerial surveys conducted for East Anglia THREE did not record seal to species level (Appendix 12.2). Over the 24 month survey period a total of two seals were recorded in the East Anglia THREE site plus buffer (in July 2012).
150. The density estimate for July 2012 was 0.027 individuals per km2 and mean density of 0.0011 individuals per km2 (Appendix 12.2).
151. The SMRU at sea densities of harbour seal are lower than the densities estimated for seal species from the APEM surveys. However, the species specific estimates made using telemetry data are likely to provide a more robust estimate to be taken forward in the assessment. This approach has been agreed in consultation with Natural England (Table 12.1).
12.5.2.2.4Summary of importance of the site for harbour seal
152. Given the site specific and contextual data described above it is considered that the East Anglia THREE site and offshore cable corridor are of limited importance for harbour seal.
12.5.2.2.5 Reference population for assessment
153. Based on the evidence from telemetry studies (UK and Dutch), the reference population will include the southeast England MU (with a population estimate of 3,567 based on the 2011 survey) and the Waddenzee region (with a population of approximately 26,788 seals, TSEG 2013b).
154. The total reference population of 30,355 harbour seal has been agreed with Natural England in consultation (Table 12.1). However, given the large difference between the UK and Waddenzee contribution to this total, impacts will also be placed in context against the UK southeast England MU.
12.5.2.3 Current stressors 155. During 1988, a major epizootic outbreak of PDV occurred causing the deaths of approximately 17,000 harbour seal in European waters. The epizootic spread from the Kattegat over several months infecting seals in the Baltic, Waddensea, North Sea
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 50
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