COSTA, DP; BURNS, JM; CROCKER, DE; FEDAK, MA; TRUMBLE, S; GALES, N: Winter Foraging Ecology of Crabeater Seals

The Antarctic marine environment undergoes considerable inter- and intra- annual variability, resulting in marked variation in the spatial and temporal availability of prey for vertebrate predators. Crabeater seals offer a unique opportunity to better understand the foraging strategies utilized by marine predators in the face of meso- and fine-scale ecological variability. As part of the US Southern Ocean GLOBEC program we deployed a total of 16 (8 tags during Fall 2001, April-May and 8 during Winter July-August 2001) satellite linked time depth recorders on crabeater seals to monitor their foraging patterns (locations and dive patterns). The seals spent considerable effort foraging, spending more than half their time at depths > 6m, and the majority of dives were deeper than 100m. The deepest dive was to 605 m a new record for this species. During the fall seals tagged in Marguerite Bay did not move with the sea ice, but remained near the tagging site, or exhibited directed movements to other regions (e.g. 220km in 8 days). Foraging was concentrated in ice-free waters of the coastal fjords or continental shelf. During the winter when sea-ice formation was greatest the seals exhibited a distinct northerly migration, such that by September only one of the 16 tagged animals remained in the area they were tagged within Marguerite Bay. Most of these animals moved to the North East along the Antarctic Peninsula. One animal moved to Anvers Island some 560 miles away.