Unprecedented Decline in North Pacific Humpback Whale Population Linked to Marine Heatwaves

A recent study published on Feb 28 has revealed concerning information about the North Pacific humpback whale population. The study indicates a drastic 20% decline in less than a decade, with marine heatwaves being identified as the potential primary cause. This news raises alarms about the future of these majestic sea creatures. 

 Since the successful conservation efforts and the end of commercial whaling in 1976, the humpback whale population in the North Pacific region had been steadily increasing until 2012. However, over the past ten years, researchers have observed a sharp decline in whale numbers, as reported in the Royal Society Open Science journal. 

 A team of 75 scientists used the largest photo-identification dataset for a large marine mammal, spanning from 2002 to 2021, to track North Pacific humpback populations. By analyzing images of the unique tail patterns of the whales, the team recorded over 200,000 sightings of more than 33,000 individuals. Contrary to expectations that the humpback population would stabilize, there was instead a significant and steep decline observed from 2012 to 2021. The number of humpbacks fell by 20%, dropping from approximately 33,000 individuals to just over 26,600. For a subgroup of whales wintering in Hawaii, the decline was even more pronounced at 34%. 

 The study highlighted the occurrence of a strong and prolonged marine heatwave from 2014 to 2016 as a critical factor in the decline. This heatwave had a significant impact on the marine ecosystem and the availability of humpback prey, leading to a more severe decline than anticipated. Study author Ted Cheeseman, a whale biologist and PhD student, expressed surprise at the magnitude of the decline. He estimated that around 7,000 whales likely starved to death during this period. 

The scientists hypothesize that the extreme marine heatwave may have reduced the carrying capacity threshold for humpbacks, resulting in a collapse in their population dynamics. The study emphasizes that a warmer ocean produces less food, affecting not only humpback whales but also other marine species like tufted puffins, sea lions, seals, and some commercial fisheries. While acknowledging the success of international restrictions on commercial whaling in the rebound of humpback populations, the study underscores the need for continued conservation efforts and climate action to ensure the well-being of these remarkable creatures.