Scottish Marine and Freshwater Science Vol 7 No 20

Since the last comprehensive assessment of grey seal diet around Britain in 2002, grey seal numbers have continued to rise in the North Sea while harbour seal numbers have declined in Shetland, Orkney and southeast Scotland. Stocks of gadid fish have also declined. In this report on task CSD3.3 of the MMSS/001/11 programme, grey seal diet is reassessed in 2010/11 and compared to previous assessments in 1985 and 2002, and estimates of prey consumed by grey seals are compared with fish stock sizes to estimate percent predation mortality. In this report on task CSD3 of the MMSS/001/11 programme, work to address the following objectives is described: • Estimate grey seal diet composition in 2010/11, regionally and seasonally; • Assess how diet around Britain in 2010/11 has changed compared to 1985 and 2002; • Estimate grey seal prey consumption in 2010/11, regionally; • Assess how consumption by seals as a percentage of estimated stock size of commercially important fish stocks in the North Sea (ICES Subarea IV) and west of Scotland (ICES Division VIa) has changed in 2010/11 compared to 1985 and 2002.