Winter foraging behaviour of lactating New Zealand sea lions (Phocarctos hookeri)

The overlap and conflict between marine mammals and fisheries is widespread and increasing globally. This study used satellite telemetry to examine the foraging patterns of lactating female New Zealand (NZ) sea lions Phocarctos hookeri from the Auckland Islands (50 degrees 50S, 166 degrees 28E), over two consecutive austral winters, 1996 and 1997. Overall, all individuals tagged were characterised as benthic foragers and were found to be diving beyond their calculated aerobic dive limits on 65% of all dives. They exhibited preferential use of the continental shelf and its edge, as they do in summer (59% overlap between winter and summer foraging areas). This study confirms that NZ sea lion foraging behaviours and areas are similar between seasons, and within and between years. Female winter foraging areas spatially overlapped by 38% with the operation areas of sub-Antarctic trawl fisheries. These findings are important because: female NZ sea lions show extreme foraging behaviour year round; and overlap with trawl fisheries is likely to occur throughout the entire lactation period of NZ sea lions. These results need to be accounted for in the management of this nationally critical, declining species.