SEASONAL CHANGE IN THE DISTRIBUTION AND DENSITY OF SEALS IN THE PACK ICE OFF PRINCESS-MARTHA-COAST, ANTARCTICA

During the period 9 December 1991-4 February 1992 shipboard and aerial surveys of seals in the pack ice off the Princess Martha Coast were m ade. All aerial surveys were flown from the MV SA Agulhas at the edge of the fast ice opposite SANAE at 70 degrees 19'S, 02 degrees 26'W. A total of 18 1/2-nm-wide transects were flown censusing 481.3 nm(-2) of pack ice within which 1437 seals were counted. The species compositio n of the seals was 94.4% crabeater, 3.4% Ross, 1.4% leopard and 0.8% W eddell seals. The density of seals nm(2) for the early season surveys (December) in the inner pack was 1.92 for crabeater, 0.0 for leopard, 0.026 for Weddell and 0.057 for Ross seals. The density for the late s eason surveys throughout the pack was 4.02 for crabeater, 0.10 for leo pard, 0.029 for Weddell and 0.122 for Ross seals. These data support t he thesis that seal densities increase as the amount of pack ice dimin ishes with the advance of summer. Leopard seals were largely found nea r the retreating outer edge of the pack, and Weddell seals associated closely with the inshore fast ice, whilst both crabeater and Ross seal s showed no statistically significant preference either for any part o f the pack ice or for any particular geographical area covered during the surveys in the present study. The high densities (0.45-2.91 seals nm(-2)) and percentage species contribution (9.7-32.4%) of Ross seals determined by shipboard censuses in the same area during the early 197 0s could not be confirmed in the present study, and it is likely that a real decrease in Ross seal numbers has taken place.