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'We need to be vigilant': Declining humpback whale population blamed on warming waters

Researchers and scientists hope this study will be a "whale-sized dose" of motivation to reduce the impacts of climate change.

Researchers are sounding the alarm after a recent study revealed a large decline in the humpback whale population.

A total of 56 international authors and more than 4,000 citizen scientists came together for the research paper on North Pacific humpback whales and discovered a 20 per cent decline in the population. 

"I was taken a little off guard by the extent of the decline that coincided with the marine heat wave,” says Tasli Shaw, lead investigator at Humpback Whales of the Salish Sea.

Researchers focused on humpback whales from 2002 through to 2021 and found that the decline was due to a marine heat wave from 2014 to 2016, also referred to as 'The Blob.'

The study focused on humpback whales in the marine waters of Alaska, British Columbia, Washington, Oregon, California, Mexico, Central America, Hawaii, Russia and Japan. 

“This took a huge effort from a lot of people and it highlights that we need to be vigilant,” says Shaw.

The study is the largest individual photo-identification dataset ever created with information coming from 46 organizations, including seven B.C.-based ones.

The Canadian Pacific Humpback Collaboration (CPHC) was involved in the study and catalogues humpback whales. The CPHC consists of the Marine Education and Research Society, North Coast Cetacean Society, the Pacific Wildlife Foundation, Ocean Wise, Humpback Whales of the Salish Sea, KETA CoastalConservation, and the Whales of Clayoquot and Barkley.

In 2012, there were about 33,500 humpbacks in the North Pacific. Average population growth was 5.9 between 2002 and 2013.

From 2012 to 2021, there was an estimated population decline of nearly 7,000 whales in the North Pacific. 

“What happens is warmer waters impact the way that the food web works, starting all the way down at the bottom with plankton. When plankton is disrupted because of warmer waters, that works its way all the way up the food chain to the prey that the humpbacks are looking for,” says Shaw. 

The study found prey availability was reduced as a result of warming waters, which led to humpback whales becoming emaciated. 

“They identified marine heat waves as a major threat to the continued success of the species,” says Shaw, adding the project was a major collaborative effort.

Shaw explains how they used HappyWhale, an AI technology, to match photographs of humpback whales’ tails in order to follow their travels. 

"So you photograph one whale off Victoria, B.C., in July and somebody in Hawaii might photograph that same whale a few months later in December,” she says. “We get this really detailed overview of not only where the humpbacks are going for their feeding season and their breeding season, but we can estimate how many there are across the entire Pacific.”

Jackie Hildering, a researcher with Marine Education and Research Society, tells Glacier Media the humpback whale population was increasing with a "humpback comeback" after whaling stopped. However, she says there were signs the population was decreasing. 

“We had local indicators that there was likely going to be a strong impact because of warming water,” says Hildering. 

She explains how her colleagues in southeast Alaska reported that humpbacks that had been coming back to that area year upon year were going missing or not showing up. 

“The whales that showed up, many of them were emaciated and there were far fewer calves,” says Hildering. 

She adds the study gives researchers a chance to understand what is going on and what threats humpback whales could face in the future. 

“Humpbacks are fantastic indicators of our human values and of how the ecosystem is doing,” says Hildering. "We have a second chance."

She’s concerned about future warming waters for the mammals and others in the ecosystem. Humpback whales may need to shift where they are feeding, she says.

“Let this be a whale-sized dose of motivation to reduce the impacts of climate change,” says Hildering. 

Shaw also hopes the study will show the public that there is a need for precaution and continued monitoring. 

“Humpbacks have to contend with these marine heat waves which are projected to be more intense and more frequent as the years go on,” she says.