It has been five years since the heatwave subsided and recently there have been some hopeful signs. Janet Neilson, co-principal researcher on Glacier Bay’s whale team, just finished writing a report summarizing the 2021 whale season and said, “In 2019, whale numbers started to climb, and in 2020 and 2021 we started to see more females with calves: equivalent to about 1 calf for every 14 whales."
However, since 2016, many whales have appeared to be unusually thin, based on a lack of fat behind the blowholes, near the shoulder-blades or along the flanks. Neilson added, “Almost all of the 11 mothers this year appeared thin, even at the end of the feeding season when they should have fattened up." Overall, these results suggest that the PMH caused long-term changes in the marine food-web that are having lingering effects on the whales.
Understanding the effects of ocean warming is increasingly important as marine heatwaves become more common and increase in severity as a result of climate change. Long term oceanographic monitoring in Glacier Bay has shown that ocean temperatures are warming by 0.1°C per decade since 1993. As whales and other marine life face growing threats to their habitat and food supply from a warming planet, protected marine areas like Glacier Bay National Park are increasingly important as a place where whales can feed relatively undisturbed. Gabriele hopes that the Park Service continues the whale study in Glacier Bay for many years to come. “Long term studies like this one are rare but essential to understanding our changing oceans. Disruptions of the marine food-web ultimately affect humans as well as other animals."
The results of the study are being published this week in the journal Mammalian Biology. Co-authors on the study are National Park Service biologists Courtney Amundson and Janet Neilson, Janice Straley at the University of Alaska Southeast in Sitka, C. Scott Baker at Oregon State University’s Marine Mammal Institute, and Seth Danielson at the University of Alaska Fairbanks.
Note to Editors: Photographs of humpback whales from the Glacier Bay humpback whale monitoring program at the following link may be used with appropriate photo credit. https://www.nps.gov/glba/learn/nature/2022-humpback-whales-media.htm
Mammalian Biology article: Sharp decline in humpback whale (Megaptera novaeangliae) survival and reproductive success in southeastern Alaska during and after the 2014-2016 Northeast Pacific marine heatwave
2021 Whale Population Resource Brief: https://irma.nps.gov/DataStore/DownloadFile/668731
Information on Alaska Marine Heatwave Effects:
Ecosystem response persists after a prolonged marine heatwave - PubMed (nih.gov)
Seabirds and Forage Fish Ecology | U.S. Geological Survey (usgs.gov)
Seabird Die-offs in Alaska | U.S. Geological Survey (usgs.gov)
Tags: humpback whale whales park science alaska marine heatwave glacier bay glacier bay national park and preserve
Source: U.S. Department of the Interior, National Park Service
