PTacific white-sided dolphins are found throughout the temperate waters of the north Pacific, from Japan to North America, and from coastal Alaska to Baja, Mexico. In Canada these dolphins were once considered a pelagic species, but since the mid 1980s they’ve been seen more and more in coastal waters. Archeological work on 2000-year-old middens in Queen Charlotte Strait uncovered dolphin teeth, suggest-ing that dolphins have had a long acquaintance with the BC coast. Absent for much of the 19th and 20th centuries, they seem to have returned, enticed perhaps by a shift in ocean temperature or by prey abun-dance.
It’s estimated that about 25,000 Pacific white-sided dolphins call our coastal waters home. But reports from boat-based surveys have been called into question because of the dolphins’ propensity for bow-riding – it’s suspected that some of these numbers are duplicates as the dolphins return to surf the wake!
Pacific white-sided dolphins travel in groups to deeper waters throughout the year. Their largest offshore aggregation was estimated at 6000 individuals. A smaller group of dolphins (100 to 200) has been sighted around the Strait of Georgia, offering scientists – and whale watchers – a great opportunity for study.
Dolphins are opportunistic predators, feeding on 60 species of fish and 20 species of cephalopods. On this coast they eat over a dozen species including salmon, herring, pollock, shrimp, sablefish, smelt and squid. They forage cooperatively, in groups large and small, corralling and herding fish.
Pacific white-sided dolphins have a gregarious nature. A California study reported that in half its recorded sightings the dolphins were in company with other species. In our inshore waters they’re often seen with resident orca whales, Steller’s sea lions, Dall’s porpoise and humpback whales. Offshore they’ve been reported with northern right whale dolphins, Risso’s dolphins, common dolphins and short-finned pilot whales. Pacific white-sided dolphins are preyed upon by transient (mammal-eating) orca whales and in some parts of their range by large sharks. Up until the early 1990s dolphins were highly impacted by gill net and drift net fisheries, many of which are now permanently closed.