How Did Tropical Dolphins End Up Off the Coast of Canada?

An unusually large group of bottlenose dolphins—a species of cetacean that normally lives in tropical and temperate waters—has been spotted off the coast of British Columbia, write researchers Luke Halpin, Jared Towers, and John Ford in a new paper in a marine biodiversity journal.

Halpin noticed the pod of approximately 200 bottlenose dolphins about 200 kilometres (124 miles) from northern Vancouver Island on July 29, 2017. “It’s about 1,000 kilometres (621 miles) north of where the species is typically found, so it is significant,” Towers, a whale researcher for Fisheries and Oceans Canada, said in a phone interview from BC.

Normally, these dolphins tap out around 35° N, off the coast of northern California. But because of rising ocean temperatures, researchers have been finding more and more tropical fish and cetaceans in northern climes. In 2015, a number of butterfish, tope sharks, ocean sunfish, and other animals were observed near BC.

A giant blob of unusually warm water originating in the Gulf of Alaska was partly to blame for those animals’ northern appearances. That blob lived from 2013–2016, though, so it doesn’t explain the July 2017 dolphin sighting. “Even though the blob was gone, the North Pacific was almost 2℃ warmer than usual,” explained Towers.

According to the researchers, it’s the only time common bottlenose dolphins have been recorded in Canadian Pacific waters and the most northern record, too. Previously, the furthest north this species was observed was in Puget Sound in Washington State. Since the late 1980s, five bottlenose dolphins have been spotted there. Only one is still alive, said Towers.

“It’s possible bottlenose dolphins have occurred in the province irregularly for decades. There’s just not a lot of people looking around,” said Towers, who has worked for the federal government’s Fisheries and Oceans department since 2006.

This time, the BC bottlenose dolphins were accompanied by about 70 false killer whales, another cetacean species that normally lives in warm and tropical waters. That it was a mixed pod isn’t so strange; bottlenose dolphins like to mingle with other cetaceans, including whales and other dolphins. Travelling together, this megapod of 270 animals was observed in mid-summer BC waters measuring 16.5℃ (61.7℉).

So, does this mean the Pacific is becoming soup?

“Kind of,” Towers said. “In this case it certainly does suggest the North Pacific is warming up, and it kind of speaks to the fact that the ocean climate is changing. Nothing is static in the environment, and this is possibly representative of that.”

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