Scats were collected in 2010/2011 up to two hours before and after low water (derived from POLTIPS, National Oceanographic Centre, NERC). Scats were placed into separate plastic bags and stored at -20°C. All scats collected were expected to be no more than two weeks old (since the last spring tide). Scat collections were stratified spatially and temporally and as weather allowed. Collections were distributed spatially in Scotland to match the Scottish Government designated Seal Management Regions (Baxter et al. 2011) and also included The Wash in south east England. All ten Special Areas of Conservation for harbour seals were included in the sampling programme. Table 1 lists all haul-out sites from which scats were successfully collected. Samples were collected in: summer (June–August, harbour seal pupping, breeding and early moult), autumn (September–November, harbour seal end of moult and start of the main period of foraging), winter (December–February, period mainly defined by foraging) and spring (March–May, pre-pupping), following Sharples et al. (2009). Table 2 shows the numbers of scats containing fish otoliths and or cephalopod beaks collected in each region/season and Table 3 shows the number of otoliths/beaks of each prey species recovered in scats, by region. Before approaching a haul-out site, the number of harbour seals was counted and any grey seals were identified and counted. Haul-out sites were designated as a single species site if the area contained =80% of one species (based on a low misclassification rate of 3% in molecular analyses to identify the species, Matejusová et al. 2013, Wilson 2014) or if the seals were spatially segregated at the haul-out site.