Antarctic fur seals in the South Shetland Islands: pup production and population trends

Discovered in 1819, the South Shetland Islands soon became the focus of intensive sealing efforts. Abundant, but never quantified, Antarctic fur seal populations were exterminated by 1874 and did not begin re-colonizing until ~80yrs later. The first reported pups born post-exploitation were found at Cape Shirreff, Livingston Island in January 1960. In 1987, an archipelago-wide aerial and ground census identified breeding colonies and substantial increases in pup production. This paper reports the results of a ground survey of all known fur seal colonies from Smith to Elephant Islands from 30 January –5 February 2002. Multiple counts of pups at each colony were conducted to establish confidence limits on pup production. Total pup production was 10,057 (±142); 85% were from Cape Shirreff (64%) and San Telmo Islands (21%). Dead pups accounted for 1.37% of the total. A comparison with previous censuses over a 15yr period (1987, 1992, 1994, and 1996) indicates the rate of increase in fur seal populations has diminished substantially. The averaged annual rate of increase from 1987-1994 was between 13.5-13.9%. From 1994-1996 it was 8.5% and from 1996-2002 the average annual rate was +0.9%. Pup production at individual colonies varied with some increasing and others decreasing. The San Telmo Islands had the largest decline from 2684 pups in 1996 to 2124 in 2002 (-3.5%/yr). Pup production at Cape Shirreff increased from 4968 to 6453 pups (5.0%/yr) during the same period. Cape Lindsey, Elephant I., and the Seal Islands had averaged annual declines of –9.4 and -6.3% from 1996-2002.