134. Not all individuals in the population are counted during surveys because a portion will be at sea at any one time. SMRU use flipper mounted transmitters to track haul out behaviour during moulting and can convert counts to total population size (Lonergan et al. 2012). From this information the total population estimate for harbour seal in the UK in 2010 was 36,500 with an approximate 95% confidence interval of 29,000 – 48,650 (SCOS 2012).
135. Approximately 4,023 harbour seal were counted around the coast of England during the most recent annual surveys. The majority are associated with colonies around The Wash (2,894) and Blakeney Point (349), which comprise The Wash and North Norfolk Coast SAC. The remaining east coast sites, Donna Nook and Scroby Sands, represent a small percentage of the UK population, with counts of 205 and 119 respectively (SCOS 2012).
136. Harbour seal are also routinely surveyed in the Wadden Sea, where populations are showing a rapid and strong growth (Reijnders et al. 2010). As part of the Trilateral Seal Expert Group (TSEG) coordinated aerial surveys are conducted in Denmark, Germany and the Netherlands. A total of 26,788 harbour seals were counted in 2013 which composed 2,759 (613 pups) in Denmark, 8,342 (3,600) in Schleswig-Holstein, 8,082 (1,373) in Lower Saxony and Hamburg, and 7,605 (1,403) in the Netherlands Wadden Sea (TSEG 2013b). These count figures represent a 2% increase from 2012 numbers and the greatest number of harbour seals recorded since the beginning of TSEG surveys in 1975 (TSEG 2013b).
12.5.2.2.1Diet
137. Harbour seal eat a wide range of prey, including sandeel, gadoids, herring, sprat, flatfish, octopus and squid (SCOS 2012). A detailed investigation in to harbour seal diet around the UK is currently being undertaken by SMRU, and should be reported in 2014 (SMRU pers. comm.).
12.5.2.2.2 At sea distribution
138. In a DECC funded survey undertaken by WWT (2009) records of seal species were shown to be sparse around the coast of East Anglia but there were frequent, low density observations offshore from the north Norfolk coast and The Wash (WWT 2009). Only one harbour seal was positively identified to species level off the coast of Great Yarmouth.
139. At sea distributions for grey and harbour seal have been produced by the SMRU (Jones et al. 2013) which utilise telemetry data from 1991-2012 and count data from 1988-2012. Mean density estimates with upper and lower 25% CIs are provided at a resolution of 5km by 5km(Diagram 12.3). There is low usage of the offshore cable
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 47
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