99.
In the UK, the breeding season is between September and December. In the Wadden Sea, November to January and, in the Baltic, February to March. Conception occurs at the end of lactation, three to four weeks after giving birth.
100. Grey seal spend a greater proportion of their time ashore during the annual moult (four months after conception) when delayed implantation of the fertilised egg occurs (Hall 2002). Densities at sea during the breeding season and moult are likely to be lower than at other times of the year (DECC 2009).
101. The European population estimate of grey seal is based on estimates of pup production. Excluding the UK, the European pup production estimate is 10,100 based on a range of survey estimates between 1994 and 2010 (SCOS 2012).
102. The UK holds approximately 38% of the world’s grey seal breeding population; estimated at 111,300 individuals (SCOS 2012). The overall population size is estimated through a population modelling approach to extrapolate survey derived pup production estimates. In the UK, the major grey seal breeding colonies in Scotland are monitored using aerial surveys by SMRU to estimate pup production. Historically these surveys were completed annually, but there were no aerial surveys undertaken in 2011. The 2010 breeding season survey is assumed to be the current best estimate, as more recent survey data are not yet published. Pup production estimates from English colonies are derived from ground count data and have unknown confidence intervals (IAMMWG 2013).
103. The main breeding site of interest for grey seal is on the east coast of England at Donna Nook in Lincolnshire, 150km from the East Anglia THREE site, which is used by a colony reported to consist of up to 3,000 adult individuals at peak times (SCOS 2012). Smaller colonies are present closer to the East Anglia THREE site on the Norfolk coast at Blakeney Point NNR (approximately 112km) and East Horsey (approximately 81km). Grey seals may also haul out at other suitable isolated beaches closer to the East Anglia THREE site, with Scroby Sands the closest reported haul out, approximately 71km from the site (SCOS 2012).
104. The total number of pups born at colonies in 2010 in the UK was estimated to be 50,174 of which of which 8,314 (16.5%) were estimated to be from North Sea colonies (including Isle of May, Fast Castle, Inchkeith, Firth of Forth Islands, Donna Nook, Blakeney Point, Horsey and the Farne Islands; SCOS 2012).
105. The southernmost colonies within the North Sea have experienced a 30% increase in pup production between 2010 and 2011 (Diagram 12.1), equating to 15% increase per annum for the last 10 years (SCOS 2012). This rate of increase indicates that
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 41
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