SANDEELS IN THE DIETS OF SEALS - APPLICATION OF NOVEL AND CONVENTIONAL METHODS OF ANALYSIS TO FECES FROM SEALS IN THE MORAY FIRTH AREA OF SCOTLAND

Serological methods for prey identification have been applied to detection of residues of sandeel (Ammodytidae) protein in faeces of common seals (Phoca vitulina) and grey seals (Halichoerus grypus) from the Moray Firth, north-east Scotland. Antisera raised to muscle protein from Ammodytes marinus were evaluated by testing their reactions with protein extracts made from a range of North Sea fish species and protein residues in in vitro digestates, seal digestive tracts and seal faeces. It was concluded that, using fused rocket immuno-electrophoresis, linkage of precipitin peaks from unknown samples with peaks from standard sandeel extract was a reliable indicator of the presence of sandeel in the unknown sample. Seasonal variation in the incidence of sandeels in common seal diet in the Moray Firth was examined by identifying otoliths, bones, and proteins, and all three methods indicated that sandeels occurred in the majority of samples tested in the summer, but were less important during the winter. Proteins were detected in fewer samples than otoliths, particularly in February and March. Possible reasons for this difference are discussed. Serological identification of sandeel proteins is potentially applicable to dietary studies on all marine predators. © 1990, Marine Biological Association of the United Kingdom. All rights reserved.