Marine heat wave deadly for starving humpback whales, study says

BySpencer Christian and Tim Didion KGO logo
Thursday, March 14, 2024
Marine heat wave deadly for starving humpback whales, study says
A new study published in the Royal Society Open Science journal estimates that some 7,000 humpbacks may have starved to death in the Northern Pacific.

SAN FRANCISCO (KGO) -- Humpback whales may put on a majestic show off our coast. But deep at sea, they've been falling prey to a changing ocean environment that could be a threat in the future. A new study published in the journal of the Royal Society Open Science now estimates that some 7,000 humpbacks may have starved to death in the Northern Pacific, with their population dropping as much as 20% over roughly a decade.

"So that's quite a turnover. And what's really a fraction of a generation for these organisms," says Peter Roopnarine, Ph.D., of the California Academy of Sciences' Institute of Biodiversity. "And so what that implies is that you have either lower rates of reproduction, so there're fewer humpbacks being born, or mortality rates are up, or both. And I suspect it's a combination of both. And so the paper argues that it's basically starvation."

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While he was not involved in the study, he is very familiar with an ocean phenomenon that may have played a deadly role, a marine heatwave, known as 'the Blob.' The event was so strong, it's believed to have increased temperatures in the Northern Pacific by as much as 7 to 10 degrees, for several years, devastating the ocean food chain.

"And you get this ramping up of competition with fewer resources, less food, all of the consumers out there competing for this food," adds Roopnarine. "And the whales now are competing directly with those other organisms like many of these fish, as well as suffering from the fact that all of these populations are going into a decline."

Bekah Lane studies risk factors for whales at the Marine Mammal Center in Marin County. She's quick to point out that Humpbacks frequenting the Bay Area coast belong to a different migration group than the northern pacific population profiled in the study. But she says warming ocean temperatures from Alaska to California have also strained the food chain for populations here, including Humpbacks and Gray whales. This often pushes them closer to our shores.

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"We are seeing them try to have more flexibility in what prey they go after, which often means that they come further in shore, which means that they're further or they're closer to human interactions like vessel strike and entanglement," Lane explains. "And that's a huge deal here. Because there's all kinds of high tech trying to do something about it."

Lane along with other researchers have helped to develop warning systems, designed to keep coastal whales safer from ship strikes. While out on the deeper ocean, researchers believe changes related to climate change could increase stresses on humpback populations in the future.

"So ocean temperatures, overall are beginning to climb," says Roopnarine. "But then also these anomalies like 'the Blob,' these heat waves, they are predicted to and this seems to be coming through predicted to become more intense, to more frequent and to last longer."

That marine heat wave known as the blob had a destructive impact along our coast as well. The Marine Mammal Center says it treated a record number of animals near its height in 2015, including a thousand starving California sea lion pups.

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