CHANGES IN THE ABUNDANCE OF NEW-ZEALAND FUR SEALS, ARCTOCEPHALUS-FORSTERI, ON THE NEPTUNE ISLANDS, SOUTH AUSTRALIA

The South Neptune Island group is a well-known site for the New Zealan d fur seal, Arctocephalus forsteri. A survey of seals in South Austral ia and Western Australia in the 1989-90 summer indicated that colonies on the South Neptunes and the adjacent North Neptunes group contained half of the breeding population in Australia. The abundance of pups a t the South Neptune group was determined in four breeding seasons: 196 9-70, 1988-89, 1989-90 and 1992-93. The population on Main Island incr eased at an exponential rate of r = 0.053 (equivalent to 5.4% per annu m) between the first two surveys: counts of pups increased from 487 to 1333, and the breeding area expanded to include several new colonies. Mark-recapture estimates of pup numbers in the two largest colonies i n 1989-90 and 1992-93 did not differ statistically. Rates of increase in individual colonies over the 19 or 20 years from 1970 ranged from r = 0.031 (3.1%) to r = 0.256 (29.2%). On the South Neptune Islands, th e estimate of pup abundance in the most recent survey (1992-93) was 19 16, on the basis of mark-recapture in most colonies and of counting in a few small ones. On the North Neptune Islands, the estimate of pup a bundance in 1992-93 was 2756, on the basis of mark-recapture in most c olonies. By applying a multiplier of 4.9 to convert pup numbers to an estimate of abundance of the whole population, estimates of 9400 and 1 3500 fur seals were obtained for the South Neptune and North Neptune I slands in 1992-93, respectively. These estimates provide a firm founda tion for comparisons in future years.