Humpback Highs and Lows Amid Shifting Seas and a Northeast Pacific Marine Heatwave: Whale Demographics in the Main Hawaiian Islands, 2002–2023

ABSTRACT North Pacific humpback whales are a celebrated conservation success, rebounding from extensive commercial whaling. Yet they remain vulnerable to the impacts of climate change, a multifaceted stressor that can exacerbate existing threats. During 2013–2016, a Northeast Pacific marine heatwave severely reduced forage availability in their feeding grounds, concurrent with diminished whale recruitment and increased mortality. We analyzed photo‐identification data of whales that visited the Main Hawaiian Islands from 2002 to 2023 to estimate apparent survival, abundance, and distinct population segment (DPS) growth rates. Survival was high prior to (0.987; SE = 0.003), low during (0.684; SE = 0.022), and higher, but still reduced, after (0.956; SE = 0.006) the heatwave. Annual breeding season abundance estimates averaged 11,617 (SD = 1914) and included a striking 37% decrease from 2014/15 to 2021/22. While the average annual DPS growth rate was stable (1.00) over 20 breeding seasons, shorter periods included high growth (1.09) and steep decline (0.783). Depressed survival and abundance estimates may signal lingering heatwave effects or adjustment to current carrying capacity. Climate change predictions include more frequent, intense, and longer heatwaves; thus, this DPS serves as a crucial ecosystem‐health indicator. Continued research and monitoring are essential to support resiliency against future climate perturbations.

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Publication Details

Journal
Marine Mammal Science
Published
2026-08-14
DOI
https://doi.org/10.1111/mms.70231
Primary Topic
Marine animal studies overview
Type
article
Field-Weighted Citation Impact
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article

Humpback Highs and Lows Amid Shifting Seas and a Northeast Pacific Marine Heatwave: Whale Demographics in the Main Hawaiian Islands, 2002–2023

Amanda L. Bradford, Ann M. Zoidis, Shannon M. Barber‐Meyer, Joseph R. Mobley et al.
Marine Mammal Science
Marine animal studies overview
article

Humpback Highs and Lows Amid Shifting Seas and a Northeast Pacific Marine Heatwave: Whale Demographics in the Main Hawaiian Islands, 2002–2023

Amanda L. Bradford, Ann M. Zoidis, Shannon M. Barber‐Meyer, Joseph R. Mobley, Adam A. Pack, Martin van Aswegen, Edward Lyman, Ted Cheeseman, Florence A. Sullivan, Rachel Cartwright, Jens J. Currie, Stephanie H. Stack, Daniel Mauricio Palacios, H. R. Spears, E. Elizabeth Henderson, Beth Goodwin, Lars Bejder, Marc O. Lammers, Meagan E. Jones, Kymberly M. Yano, Marilia Olio, Chris Gabriele, Jay P. Barlow, Lewis Evans, M. Deakos, S. Yin, R. Finn, D. M. McSwain, C. Hayslip
article en

Abstract

ABSTRACT North Pacific humpback whales are a celebrated conservation success, rebounding from extensive commercial whaling. Yet they remain vulnerable to the impacts of climate change, a multifaceted stressor that can exacerbate existing threats. During 2013–2016, a Northeast Pacific marine heatwave severely reduced forage availability in their feeding grounds, concurrent with diminished whale recruitment and increased mortality. We analyzed photo‐identification data of whales that visited the Main Hawaiian Islands from 2002 to 2023 to estimate apparent survival, abundance, and distinct population segment (DPS) growth rates. Survival was high prior to (0.987; SE = 0.003), low during (0.684; SE = 0.022), and higher, but still reduced, after (0.956; SE = 0.006) the heatwave. Annual breeding season abundance estimates averaged 11,617 (SD = 1914) and included a striking 37% decrease from 2014/15 to 2021/22. While the average annual DPS growth rate was stable (1.00) over 20 breeding seasons, shorter periods included high growth (1.09) and steep decline (0.783). Depressed survival and abundance estimates may signal lingering heatwave effects or adjustment to current carrying capacity. Climate change predictions include more frequent, intense, and longer heatwaves; thus, this DPS serves as a crucial ecosystem‐health indicator. Continued research and monitoring are essential to support resiliency against future climate perturbations.

Marine Mammal ScienceVol. 42(4)
Griffith University (AU), University of Hawaiʻi at Mānoa (US), Oregon Research Institute (US), Naval Information Warfare Center Pacific (US), University of California, Santa Cruz (US), Whale Museum (US), Bamfield Marine Sciences Centre (CA), University of Hawaii at Hilo (US), Clinical Research Organization (BD), Istituto di Scienze Marine del Consiglio Nazionale delle Ricerche (IT), NOAA National Marine Fisheries Service Pacific Islands Fisheries Science Center (US), Center for Whale Research (US), Center for Coastal Studies (US), NOAA Office of National Marine Sanctuaries (US), Cascadia Research Collective (US), Monk Seal Foundation (US), Keihin (Japan) (JP)
Whaleman Foundation, Marine Mammal Commission, National Marine Sanctuary Foundation, Volgenau Foundation, National Oceanic and Atmospheric Administration, U.S. Geological Survey, Office of Naval Research, National Marine Fisheries Service, Office of National Marine Sanctuaries
Climate action
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Marine animal studies overview
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