We present definitive evidence, derived from two independent methods (satellite tagging and photo-identification), that TCKW undergo long-distance travel from the southern Ross Sea to New Zealand waters and into subtropical regions (31°-35°S). This not only establishes ecosystem connectivity between the Ross Sea and New Zealand, but also emphasises the urgent need to re-evaluate the profile of potential threats faced by, and capacity for resilience in, this top predator. Together with Weddell seals, TCKW have been identified as one of the two top predator species in the Ross Sea most likely to be affected by the Ross Sea fishery for Antarctic toothfish, Dissostichus mawsoni, but critical knowledge gaps regarding abundance, diet, foraging habitat, and movement patterns limit our ability to assess or manage risk to TCKW.
New results from satellite transmitters deployed on TCKW in Terra Nova Bay suggest that TCKW may use small-scale areas in this highly productive ecosystem intensely for a period of days to weeks, but also undergo rapid long-distance travel along a northward transect towards New Zealand and the Kermadec Trench. Dive records from these tagged TCKW (n=4) indicate that whales perform deeper dives while in Terra Nova Bay (100-455 m) than on the northbound journey. A preliminary analysis of photo-ID data indicates that TCKW show a high degree of seasonal site fidelity, with whales inter-annually returning to areas of ecological significance, including New Zealand waters north and east of East Cape, the Kermadec Trench region, and highly productive Antarctic areas providing access to silverfish and toothfish (or other, yet unidentified prey resources).
The unexpectedly complex movement patterns and extremely broad spatial scale of movement exhibited by TCKW have important implications for our understanding of the ecology of this key Ross Sea predator, and for the precautionary spatial management of the Ross Sea regions, including monitoring of the existing ASPA #173 Silverfish Bay and the establishment and ongoing monitoring of the proposed Ross Sea Marine Protected Area. These research priorities would be best addressed by multi-national collaborative efforts coordinated through the frameworks of IWC SORP and CCAMLR.