Growth in the Antarctic fur seal Arctocephalus gazella

The growth of the Antarctic fur seal Arctocephalus gazella at South Georgia is described from 556 specimens whose age was determined. The following parameters are described: standard length, body weight, foreflipper length, hindflipper length, neck girth, axillary girth and blubber thickness. Data are also presented on absolute and relative sizes of the following organs in new‐born pups, pups near weaning, two‐year‐olds and adults: thyroids, adrenals, heart, lungs, kidneys, liver, spleen and brain. The growth of the pup within the 110–115 day suckling period is estimated as 98 g/day for males and 84 g/day for females. No other species of fur seal grows so rapidly at this time. Subsequent growth is compared with that of the other species of fur seal to inhabit polar water, Callorhinus ursinus. A. gazella grows more rapidly up to age three, and although adult males are smaller, females are slightly larger. This more rapid initial growth, and earlier breeding, may be related to the large reduction in the Antarctic stocks of baleen whales which eat the same food. The mean weights of males, females and all individuals in the population are calculated as 54‐8,25‐3 and 39‐3 kg respectively. The number in the population at the end of the breeding season is 41 times the number of pups born, equivalent to a total population in March 1976 of 369,000 seals with a biomass of 14,500 tonnes and an annual food consumption of about 350,000 tonnes.