320 J. D. LOCKIE 



Scales and otoliths therefore do not appear and in order to identify such 

 remains the seal must be killed before digestion has proceeded far. Again, 

 the food of young seals may be different from that of older seals. Bearing 

 these points in mind, the following food was found (Table III), the identifica- 

 tion being from bones, flesh, otohths and the homy beaks of cephalopods. 

 Dr Bennet Rae has kindly checked the identification of otoliths and has 

 estimated the weight offish whence they came. Likewise Dr A. C. Stephen 

 kindly provided estimated weights of cephalopods of the size found in these 

 seals. 



Table III. Food identified in eight grey seals 

 (age groups one to four years, June-August (1956-7) 



Estimated weight 



of prey 



(oz) 



Gadusspp no 



Cephalopods {Loligo forbesi and Eledone cinerosa) . 296 



Salmon or sea-trout {Salmo truttd) ... 80 



Total 406 



Proportion by weight of salmon and/or sea-trout = 19-7 per cent. 



Amount eaten. The amount eaten by common seals {Phoca vitulina) and grey 

 seals per day has been estimated by Steven (i934» 193^) to be 10 lb (4* 5 kg) 

 and 15 lb (6- 8 kg) respectively. Likewise the sea hons {Zalophus californianus) 

 in the Edinburgh Zoological Gardens are given an average of 14 lb (6- 3 kg) 

 of haddock {Gadus aegkfinus) per day. If 15 lb per day offish is a reasonable 

 figure for mature grey seals, immatures and yearlings must take less. 



Seal pups make httle extra growth in their first year (Telfer & Watt, 

 1953) and may weigh no more than 100 lb (45 kg) at forty-six weeks. 

 5 lb per day for yearlings and 12 lb per day for immatures may be a reason- 

 able guess of their food requirements. 



That being so, we can make a very rough calculation of the amount of 

 salmon eaten by immature grey seals and young bulls in the study area 

 during the 1957 salmon-fishing season (182 days). 



Twenty-nine yearhng seals at 5 lb per = 29 X 5 X 182 = 26,390 lb 



day 

 Thirty-five two- to five-year-old =35 X 12 X 182= 76,440 



seals at 12 lb per day 

 Three young bulls at 15 lb per day = 3 X 15 X 182 = 8,190 



Total 111,020 lb 



