This sighting of a large group of common bottlenose dolphins off the northwest coast of Vancouver Island is the first confirmed occurrence of the species in Canadian Pacific waters despite significant aerial and ship-based survey effort over the past 15 years (Ford et al. 2010; Nichol et al. 2017; Williams and Thomas 2007). There are also no stranding records for the species in British Columbia (Ford 2014). The location of this sighting is approximately 1000 km north of the typical range of common bottlenose dolphins off the west coast of North America, and represents the northernmost record of the species in the eastern North Pacific. An estimated 200 dolphins were present in this group, which is an unusually large aggregation – group sizes of both inshore and offshore ecotypes of the species off California typically average 10–20 animals and large aggregations occur in offshore waters (Wells and Scott 2018; Barlow 2016; Jefferson et al. 2015; Defran and Weller 1999). Considering that the common bottlenose dolphins reported in the present study were observed offshore traveling closely with false killer whales, a typically offshore species, they likely represent the offshore North Pacific ecotype. However, in the absence of genetic analysis, the ecotype of the dolphins in the present study remains speculative.
The presence of a large group of false killer whales mixed with these common bottlenose dolphins is a significant record for that species as well. False killer whales are a warm-temperate to tropical species that occurs mostly in deep, offshore waters. In the eastern North Pacific, false killer whales typically do not range north of 35°N (Chivers et al. 2007). The species was not recorded during a series of extensive cetacean surveys undertaken off the United States mainland west coast from California to Washington State during 1996–2014 (Barlow 2016; Barlow and Forney 2007). In Canadian Pacific waters, there are numerous sighting records of false killer whales, but most are related to a single group of about a dozen animals that entered inshore waters of southern British Columbia in 1987 (Ford 2014). Otherwise, the only other records of false killer whales in the Canadian Pacific are a single neonate that was live-stranded along the west coast of Vancouver Island in July 2014 (Laanela 2014), and whistles characteristic of the species were detected on a recording instrument off the northwest coast of Vancouver Island in August and September, 2010 (Ford 2014).
Other species primarily known from warm waters south of B.C., such as short-beaked common dolphin (Delphinus delphis) and long-beaked common dolphin (D. capensis), dwarf sperm whale (Kogia sima), pygmy sperm whale (K. breviceps), and short-finned pilot whale (Globicephala macrorhynchus) have also occasionally been documented in the province (Ford 2014). However, the occurrence of these species is rare and, like common bottlenose dolphins and false killer whales, they can be considered vagrant, accidental or associated with changing ocean conditions, for example, due to climate change.