Summary
The Antarctic Pack-Ice Seals program (APIS) is an initiative of the SCAR Expert Group on Seals aimed at quantifying the role of pack-ice seals (crabeater, leopard and Ross) in the Southern Ocean. A central feature of APIS was a synoptic, circumpolar survey of pack-ice seal abundance and distribution through a co-ordinated, multi-national effort. We present here results of the Australian survey effort in a 1.5 million km2 region off east Antarctica between longitudes 60-150oE in 1999/00. The survey presented a unique set of logistical, methodological and analytical challenges. Survey methods comprised sighting surveys from aircraft and ships to estimate the abundance of hauled out seals, and studies of haulout behaviour using satellite transmitters to assess the proportion of seals in the water and hence ‘unavailable’ for survey. Weather and ice conditions prevented random sampling of the pack-ice from ships and aircraft. Consequently, extrapolation from sampled areas to the entire region was not possible using traditional design-based methods, and spatial modelling was instead employed. The uncertainty in abundance estimates was estimated from bootstrapping of the estimation process. Estimates of abundance will be presented and discussed in relation to previous knowledge.