Annual food consumption, and seasonal fluctuations in biomass of seals at Marion Island

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Abstract
Recent population estimates and annual haul out cycle data for the 3 spp. of seals which occur on Marion Island (Mirounga leonina, Arctocephalus tropicalis and A. gazella) were studied. These data have enabled estimation of the number of seals, of each species, that haul out each month on the island, and by making use of published and unpublished data on body mass, it has also been possible to estimate the seal biomass hauled out each month. Total population biomass of M. leonina was estimated to be 14,207 .times. 102 kg, for A. tropicalis 2529 .times. 102 kg and for A. gazella 124 .times. 102 kg. Maximum seal biomass occurred on the island in Jan. (11,870 .times. 102 kg). From Nov.-April most elephant seal biomass occurred inland in molting areas and on the beaches from the rest of the year. Mean monthly unit mass for elephant seals hauling out was 353.9 .+-. 137.6 kg. 33.7 .+-. 7.4 kg for A. tropicalis, and 46.9 .+-. 10.1 kg for A. gazella. Annual food consumption for all species was estimated to be 346,353 .times. 102 kg, of which M. leonina consumed 82%. Of the total food biomass consumed annually by all species, fish comprised .apprx. 29%, squid 70% and krill 1%.

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