Marine heatwave likely caused sharp decline in Hawaiian humpback whales, study finds

A study analyzing over 27,000 whale-fluke photos from the citizen-science platform Happywhale found the Hawaiian humpback whale population dropped 37% between the 2014-2015 and 2021-2022 breeding seasons, coinciding with a 2013-2016 marine heatwave that devastated forage fish and krill in the northeastern Pacific. Adult survival rates, normally around 99% annually, fell to an estimated 68% during the heatwave, and researchers documented whales starving in Alaska and British Columbia.

Roughly 5,000 fewer humpbacks were counted after the heatwave, though researchers can't rule out some relocated rather than died. The population still hasn't recovered, leaving it more exposed to entanglements, ship strikes and pollution.

The North Pacific is again experiencing a marine heatwave alongside a strong El Niño, raising concern the pattern could repeat. Researchers noted similar declines in gray whales tied to Arctic ice loss, suggesting a broader trend across species.

The full dispatch is available from the source below.