Dwindling salmon stocks mean endangered B.C. orcas are going hungry, researchers say

Orcas are one of the biggest ocean predators, but in the waters off B.C.'s coast, researchers say the hunters are going hungry.

According to a new study from the University of British Columbia, endangered southern resident killer whales are missing thousands of their much needed daily calories. 

"They are not getting 28,716 calories, or about 17 per cent of what they need daily," said the study's lead author, Fanny Couture. "If we talk about humans, we will say that it's the equivalent of missing about one meal per day."

Couture is a marine ecologist with UBC's Institute for the Oceans and Fisheries. She says the orcas have been in an alarming and consistent "energy deficit" since 2018.

"That means the whales used up more energy than what they consumed from food, and they are very big animals with big energetic demands," she said.

With fewer than 80 left in the wild, southern residents are the smallest orca population in the Pacific Northwest. They have not only been an iconic fixture in B.C., but are culturally significant to west coast First Nations.

Along with her team, Couture reviewed data from 1979 to 2020, in order to analyze the abundance, age and size of the different salmon species the orca's consume.

"Chinook salmon represents up to 90 per cent of their food source, and we do know their populations have been dwindling as well," she said.

Wild Chinook, also known as king salmon, are prized for their large size; however, their stocks are in steep decline.

According to the Pacific Salmon Commission, which is a joint regulatory body run by Canada and the United States, Chinook salmon populations "are down 60 per cent" since 1984. 

Fisheries and Oceans Canada cites a number of factors for a drop in the salmon population, including "habitat destruction, harvest and the effects of climate change."

"There is a real urgency with all of this because the killer whales and the Chinook are so connected, and we need to really understand what is happening with both the prey and the predator," Couture said.

Scientists say orcas are not a fasting species, and depending on their size, need to consume about 200,000 calories a day. With such high energy demands, a food shortage can devastate a population.

"They share their food, almost compulsively, so the whole group tends to suffer and get thin if there is food depletion," said Lance Barrett-Lennard, a senior scientist with the Raincoast Conservation Foundation.

Barrett-Lennard has been studying orcas for more than 30 years and also co-authored the UBC study.

"When they go through these periods of not having enough food and being in very poor shape, it can impact their ability to hunt, reproduce and grow in size."

Barrett-Lennard says it is often young orcas most impacted when food is scarce, adding if they are not properly nourished during the first three years of life, "they can be around a meter shorter in length by the time they are fully grown."

In 2019, the federal government announced an "enhanced recovery strategy" for the southern resident whales that includes area-based fishing closures to increase Chinook salmon availability if orcas forage the areas. 

In April, Ottawa put in place more measures to protect the whales in hopes of boosting their dwindling numbers, but many scientists say more needs to be done to address the food shortage.

"There has been a lot of effort and money into trying to save the endangered southern residents, but clearly need to do more because the population is not recovering," Barrett-Lennard said. "They need safe places where they can forage, and we need to keep working on increasing the salmon supply for them."

As for the new study, Couture says she hopes it highlights that both killer whales and Chinook salmon are "important, iconic species for the west coast of Canada."