We conducted 101 whole prey feeding trials with six harbour seals (Phoca vitulina) and 18 prey species to derive estimates of digestion coefficients (DC; accounting for partial digestion using otolith width (OW) or length (OL)) and recovery rates (RR; accounting for complete digestion). Greater than 98% of otoliths were passed within 3 days of consumption. All otoliths passed were recovered by day 10 and all beaks by day 14. RRs were smallest for Atlantic salmon smolts (Salmo salar, RR=0.306; SE=0.031), progressively greater for sandeels, flatfish, squid (Loligo forbesii) and large gadoids, and greatest for Trisopterus spp (RR=1.017, SE=0.002). Species-specific DCs were greatest for greater sandeel (Hyperoplus lanceolatus, DC(OW)=1.75, SE=0.049), then progressively smaller for sandeel, flatfish, large gadoids and Trisopterus species (DC(OW)=1.14, SE=0.015). The amount of erosion of each otolith was graded using a scale of 1-4. The majority of otoliths recovered (65.9%) were severely eroded (grade 4). Grade specific DCs were greatest for greater sandeel (DC=1.82, SE=0.047), then progressively smaller for large gadoids, flatfish and Trisopterus spp (DC=1.18, SE=0.016). Possible explanations for some results with RR>1 and DC<1 are discussed. In almost all cases the CV was smaller for DCs using OW than using OL. As such, OW DCs (grade-specific) will be used to estimate the diet of harbour seals, where possible. RRs were broadly similar to those for grey seals (Halichoerus grypus), but harbour seal species- and grade-specific DCs were generally smaller. Differences in partial and complete digestion rates among prey species and between harbour and grey seals highlight the importance of applying predator- and prey-specific digestion correction factors when reconstructing diet.