J. CETACEAN RES. MANAGE. 1 Killer whale studies, McMurdo Sound, Ross Sea, Antarctica, Jan-Feb 2014 1 Regina Eisert, 2 Paul Ensor, 3 Rohan Currey 1 Gateway Antarctica, University of Canterbury, Christchurch, NZ 2 33 Governors Bay-Teddington Road, Governors Bay, RD1 Lyttelton 8971, NZ 3 Ministry of Primary Industries, Wellington, NZ ABSTRACT Ecotype B and C (TBKW, TCKW) killer whales (Orcinus orca) were studied in McMurdo Sound, Antarctica, in late January and early February 2014. While the unusually extensive break-out of the sea ice in the 2013-14 season limited opportunities for the collection of dart biopsies, three whales were sampled. In the period from 20-28 January, a total of 307 whales were detected including 297 TCKW and 10 ecotype B killer whales (TBKW) along a 20-30 nautical mile stretch of fast ice at the western margin of McMurdo Sound. Feeding behaviour of TCKW was recorded during 5 of the 8 flights. TCKWs with prey items held in their jaws were seen on 5 occasions; in 3 cases, the prey was clearly identifiable as toothfish (Dissostichus mawsoni). A large number of images were collected for photo- identification. Additional observations of hunting behaviour of Type B killer whales directed at seals and penguins were made from Scott Base between 30 Jan and 16 Feb 2014. KEYWORDS: ANTARCTIC, KILLER WHALE, ECOTYPES, FEEDING, PHOTO-ID, TOOTHFISH, MINKE WHALE INTRODUCTION In January 2014, killer whale research was conducted in McMurdo Sound, Ross Sea, Antarctica, as part of a collaborative study of megafauna trophic relationships led by the University of Canterbury and funded by the New Zealand Antarctic Research Institute (NZARI RFP 2013-1). The aim was to study the diet of killer whales (Orcinus orca), Weddell seals (Leptonychotes weddellii) and Adélie penguins (Pygoscelis adeliae) as key predators of the region. The killer whale component focussed on ecotype C killer whales (sensu Pitman & Ensor 2003). This ecotype has a wide distribution in Antarctic waters and in the Austral summer is particularly abundant in the shallow waters of the Ross Sea. Ecotype C killer whales (TCKW) are postulated to feed primarily on fish based on analyses of stomach contents from Soviet whaling (Berzin & Vladimirov 1983; Pitman & Ensor 2003), although neither the species of fish nor the ecotype of whale examined were reported. There are a two reports of killer whales feeding on Antarctic toothfish Dissostichus mawsoni in channels in the sea ice made by US icebreakers operating in McMurdo Sound during the austral summer (Thomas et al. 1981; Wu & Mastro 2004) as well as an observation near the ice edge in Terra Nova Bay (Ainley et al. 2009), suggesting that toothfish may be an important prey item for TCKW. However, TCKW have also been reported to feed on Antarctic silverfish SC/65b/SM06