Seasonal variation in body condition of adult male hooded seals (Cystophora cristata) in Skjalfandi-Bay, northeast Iceland

Abstract

This study examined seasonal changes in blubber distribution and body morphology of 61 male hooded seals, 4 years of age and older, caught in Skjalfandi-Bay in northeast Iceland in May, August and October during 1998 and 1999. Seasonal changes were found in girth, blubber depth and the ratio of blubber depth to body radius (d/r ratio). The seals lost 16% of their total mass between May and August, during moulting, but d/r ratios did not drop significantly. Hooded seals caught in October were 10% heavier than seals caught in August mostly due to greater sculp mass but were not as heavy as seals caught in May that had a higher core mass (mass–sculp). Core mass decreased by 14% between May and August or almost proportionally to total mass but increased much more slowly than total and sculp mass between August and October. Furthermore, this study found that commonly used condition indices are misleading when comparing condition of adult male hooded seals between seasons.