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Belugas absent from Kenai River during peak fishing season

Endangered Cook Inlet beluga whales, which have traditionally fed in the salmon-rich Kenai River throughout the summer, were absent during times of high human activity in a recent two-year period.

A team led by Sonia Kumar, a Ph.D. student at UAF’s ���ϳԹ��� of Fisheries and Ocean Sciences, spent two years tracking belugas in the Kenai and Kasilof rivers using underwater microphones. The team included researchers with the UAF ���ϳԹ��� of Fisheries and Ocean Sciences and the National Oceanic and Atmospheric Administration.

Belugas have historically fed in the two Cook Inlet rivers from April to November. However, the hydrophone data found they were much less likely to be present throughout the summer fishing seasons, when a busy swarm of people arrive each year in search of salmon.

“Commercial fishing, personal-use dipnetting, sport fisheries, seafood-processing companies — there’s just a ton of activity going on,” Kumar said.

Based on hydrophone data from 2021 and 2022, researchers determined that belugas were largely skipping the peak of the sockeye salmon run on the Kenai River, when the area is busiest. They were more likely to feed in the Kenai in the fall, when human activity was low. Belugas weren’t detected in the Kasilof River at any time.

The study .

Researchers have worked to learn more about Cook Inlet beluga behavior amid a decades-long decline in their genetically distinct population. An estimated 331 belugas lived in the inlet year-round during the most-recent survey in 2022, roughly a quarter of the number that were present in the late 1980s.

While the Cook Inlet beluga population has stabilized in recent years, researchers are still working to better understand the causes behind that drop.

“We have a population that has room to expand and recover, and they’re not,” said Lara Horstmann, a UAF marine biology professor who participated in the study. “There’s certainly room to understand what’s impeding their recovery.”

Researchers cautioned that the findings don’t definitively point to human-caused activity as the reason belugas aren’t using the Kenai and Kasilof rivers in the summer. Because of the low population numbers, there is less competition among Cook Inlet belugas than in the past. The remaining whales may bypass the Kenai River because they have the luxury of feeding in areas where prey abundance might be higher.

“It’s not a black-and-white issue,” Kumar said. “Because their population is small, belugas may have their pick of where the most optimal foraging location is. There’s a happy middle ground where we can all be in this ecosystem together, and we need to figure out what that is.”

ADDITIONAL CONTACTS: Sonia Kumar, svkumar@alaska.edu; Lara Horstmann, lahorstmann@alaska.edu

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