ICES CM 2008/B:20 Distribution and Movement Patterns of Killer Whales (Orcinus orca) in the Northwest Atlantic Tara S. Stevens1,2 and Jack W. Lawson1 (1) Fisheries and Oceans Canada, NAFC, 80 East White Hills Road, St. John’s, Newfoundland and Labrador A1C 5X1, Canada (2) Memorial University of Newfoundland, Cognitive and Behavioural Ecology Program, St. John’s, Newfoundland and Labrador A1B 3X7, Canada Corresponding author e-mail: [email protected]

ABSTRACT: Killer whales (Orcinus orca) occur throughout the northwest Atlantic. A sightings database and photographic catalogue, created mostly from opportunistic sources, is used to examine the occurrence of killer whales in Atlantic Canada. A majority of the sightings are from the Newfoundland and Labrador Region despite comparable observer coverage in adjacent areas such as the Gulf of St. Lawrence and Scotian Shelf, which suggests greater abundance in and habitat preference for Newfoundland and Labrador waters. Killer whales occur in all months of the year and in both near- and offshore regions, although particular sighting patterns may represent local observer effort and awareness. The distribution, movement, and residency patterns of killer whales may be closely linked to that of their prey; they have been observed harassing, attacking, and eating marine mammals, including minke whales (Balaenoptera acuterostrata), dolphins, and seals, and potentially eating fish. Some killer whales appear to remain year round in the Newfoundland and Labrador area and have been sighted during the spring within pack ice, potentially in association with breeding harp seals (Phoca groenlandica). Based on photographic records, individual killer whales in this area have been shown to move hundreds of kilometers within a year. Conversely, although there is no spatial or temporal evidence of seasonal migration, killer whales may be reliably seen in certain areas during particular times of the year, suggesting that long-term site fidelity patterns may exist within this population.

Figure 2: Killer whales in three separate encounters off St. Pierre attacking and/or consuming (counter-clockwise from top): minke whale (Balaenoptera acuterostrata), white-beaked dolphin (Lagenorhynchus albirostris), and unknown rorqual species. Figure 3: NW Atlantic subdivided into DFO regions. METHODS: The Atlantic Canada killer whale photo-identification catalogue and sightings database were used in this study to document and analyze the distribution and movement patterns of killer whales in the NW Atlantic. The photographic catalogue is used to identify individuals while the sightings database is used to maintain all temporal, geographic, and behavioural data associated with encounters. There are over 40 contributors to the photographic catalogue and several hundred to the sightings database.

RESULTS: • There are 348 sightings of killer whales in Newfoundland and Labrador, 25 in the Gulf of St. Lawrence, and 43 in the Scotian Shelf/Bay of Fundy regions. • There are 10 sightings of killer whales in the presence of ice around Newfoundland and Labrador. • There are 46 catalogued individuals in the Atlantic Canada killer whale catalogue, plus many yet unmatched photographs. • A majority of the encounters documented with photographs occurred in nearshore waters in few locations around Newfoundland and Labrador. Figure 1: Sightings of killer whales in the NW Atlantic from 1864–2008. • There are 30 foraging-related accounts, which include eight predation or attempted predation events on minke whales, three on humpback whales, possibly three on fish, and at least five scavenging-related events.

Catalogue photograph Whale ID Dates sighted Locations sighted NF0002 11 August 2004…………………... Battle Harbour 07 September 2004………………. Battle Harbour 08 September 2005………………. Battle Harbour 30 April 2006……………………. St. Pierre 19 July 2006……………………… Battle Harbour 22 August 2007..…………………. Battle Harbour NF0007 09 August 2005………………….. L’Anse aux Meadows 14 August 2005………………….. St. Anthony 19 July 2006……………………… Battle Harbour 07 September 2006………………. Battle Harbour 30 June 2007…………………….. St. Pierre 29 July 2007……………………… Fogo Island NF0009 09 August 2005………………….. L’Anse aux Meadows 14 August 2005………………….. St. Anthony 07 September 2006………………. Battle Harbour 21 June 2007…………………….. St. Pierre 30 June 2007…………………….. St. Pierre NF0010 2001……………………………… Bonavista 11 August 2004………………….. Battle Harbour 09 August 2005………………….. L’Anse aux Meadows 14 August 2005………………….. St. Pierre 19 July 2006……………………… Battle Harbour 07 September 2006………………. Battle Harbour 26 August 2007………………….. St. Anthony Table 1: Sighting history of four frequently-sighted killer whales. Notice the spatial and temporal range of movements, plus potential site fidelity patterns. Figure 4: Sightings distribution of identified killer whales around Newfoundland and Labrador through 2006.

CONCLUSIONS: Geographic Distribution: Killer whales are sighted throughout the NW Atlantic although, based on the sightings database, there are considerably more sightings in the Newfoundland and Labrador Region than in other areas of Atlantic Canada. This may represent a habitat preference for the Newfoundland and Labrador Region. Temporal Distribution: Killer whales are sighted throughout the year in Newfoundland and Labrador, including during the winter months in the presence of sea ice and breeding harp seals. Movement and Residency Patterns: Killer whales move hundreds of kilometers within a year and also exhibit site- fidelity patterns in certain areas during particular times of the year. Minke whales appear to constitute a potentially considerable portion of killer whale diet in this region. The movement and residency patterns of killer whales may be closely linked to that of their prey.

Figure 5: DFO researcher photographing male killer whale NF0040 in St. Anthony in 2006. Inset shows the same male photographed by DFO off St. John’s in 2008.