SEASONAL AND GEOGRAPHIC-VARIATION IN THE SPECIES COMPOSITION AND SIZEOF PREY CONSUMED BY GRAY SEALS (HALICHOERUS-GRYPUS) ON THE SCOTIAN SHELF

The grey seal (Halichoerus grypus) population on the Scotian Shelf has grown significantly over the past 20 yr, thus increasing the potentia l for competitive interactions between grey seals and fisheries. The r elative contribution (percent wet weight) and size of prey eaten were estimated from otoliths and squid beaks recovered from 143 stomachs th at contained food of the 528 collected from 1988 to 1990. Although 22 taxa were found, only four species (Atlantic herring, silver hake, Atl antic cod, and squid) accounted for 80% of the estimated weight of foo d eaten. The mean length of prey eaten ranged from 19 to 35 cm for six species. Only 17% of the cod and none of the pollock and squid eaten were of the length taken in commercial fisheries. However, about 80% o f the silver hake and herring eaten were of commercial size. Offshore at Sable Island, northern sand lance, silver hake, and squid (in order of importance) accounted for 86.1% of the wet weight ingested by seal s during summer; sand lance and cod accounted for 96.1% of prey eaten in winter. At inshore locations, herring, cod, and pollock made up 90% of the diet in summer; Atlantic mackerel, cod, squid, and herring mad e up 83% of the diet in winter.