Spring is one of Christine Gabriele’s favorite times of year. She spends her days in and around Glacier Bay National Park, watching as the area’s humpback whales return after wintering overseas.
“It’s like taking attendance and seeing your old friends,” said Gabriele, who has been a whale biologist in the park for nearly four decades.
This year, she’ll be keeping her eye out for two whales in particular: A male that would be returning for his 53rd year and a female that was one of the first whales Gabriele learned to identify as a young scientist.
“She was missing last year,” Gabriele said. “I hope that she’s not gone for good, because she’s one of my favorites.”
Gabriele is part of a small team charged with studying the humpback population in Glacier Bay and nearby Icy Strait. A major theme of their recent work has been studying how the whales are doing after a marine heatwave between 2014 and 2016 devastated marine environments up and down the west coast, including the Gulf of Alaska.
By 2018, the area’s humpback population had declined by more than 50%. Last summer, it was still 33% lower than before the heatwave struck the area, according to a research update published earlier this spring.
“Lingering impacts from the [Pacific Marine Heatwave] suggest there will be reduced humpback whale population growth in the coming years, even if feeding conditions are favorable,” the report says.
That’s due to a range of factors. Among them: None of the calves born in 2014 were ever seen again. And just one of 22 whales born between 2014 and 2018 is known to have survived. That means they won’t go on to reproduce.
Another factor is the whales’ rate of reproduction, which Gabriele said went “really, really low” after the heatwave. Before the event, one in three females had calves each year, on average. In the immediate aftermath, about one in 25 were having calves per year.
Things have improved since then but still aren’t back to where they were. On average, about one in 12 females are now giving birth each year.
While female whales used to have their first calves at around age 11 or 12, more seem to be waiting until age 15, 16 or 17. On top of that, they’re waiting eight or nine years between calves instead of two or three.
“Those are the things that are causing the population to grow slowly,” Gabriele said.
Underlying all of those factors is that the marine environment is changing. The whales seem to have a less reliable food supply, which could explain why reproduction is happening less often.
Answers about the status and trajectory of that food supply could be coming. The Park Service is working on monitoring the forage fish population — small, energy-rich fish, like herring and capelin. Gabriele said the research will provide invaluable insight into the food supply, which affects seabirds, bears, whales and, of course, Alaskans.
“Really it’s just one jump away from the salmon on my dinner plate to the krill and the fish that the whales are eating,” Gabriele said. “When the whales are doing well, we’re doing well.”
