ORGANOCHLORINE RESIDUE CONCENTRATIONS AND BURDENS IN GRAY SEAL (HALICHOERUS-GRYPUS) BLUBBER DURING THE 1ST-YEAR OF LIFE

Between 1988 and 1991 grey seal (Halichoerus grypus) pups at various d evelopmental stages were sampled at Sable Is., NS, and blubber samples were analysed for lipid content and organochlorine (OC) residue conce ntrations. Blubber lipid content increased significantly between birth and 12 d, and then stayed relatively constant. Blubber OC residue con centrations were fairly constant during the first 12-16 d of life. Fro m weaning (approx. 16 d) until four months, the pups are learning to f eed but are relying on blubber fat reserves; thus, during this period blubber weight declined to minimum levels, and OC residue concentratio ns in blubber lipid increased significantly. Blubber lipid OC concentr ations then declined slightly as the pups gained weight, until at the end of one year they were about twice those immediately post-weaning. Blubber lipid residue burdens calculated from these data showed that a t weaning, about 98% of the seal's residues were accumulated from mate rnal milk. After weaning, there were no significant changes in the bur dens of any residue until the end of the first year of the pup's life, and the organochlorine concentration changes reflected a fairly const ant organochlorine burden around which lipid contents varied. These da ta suggest that the capacity of the seal to degrade the residue inheri ted from its mother is very limited. Furthermore, the absence of any s ignificant accumulation of organochlorines during the second six month s of the seal's life suggests that the juvenile seal must feed at a lo w trophic level which is not highly contaminated with organochlorines.