First long-term acoustic study sheds new light on Cook Inlet beluga behavior

 Belugas spotted in Ship Creek (Courtesy Peter Scully)
Belugas spotted in Ship Creek (Courtesy Peter Scully) (KTUU)
Published: Feb. 24, 2020 at 5:18 PM AKST
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Biologists trying to piece together the puzzle of why the endangered Cook Inlet beluga whale population continues to decline despite recovery efforts now have more information they hope will lead to answers.

This month researchers with NOAA Fisheries, Alaska Department of Fish and Game, the University of Washington and other partners published findings from the first long-term acoustic monitoring in Cook Inlet, shedding light on the seasonal distribution of the animals and where they feed.

"In summer it's easier to monitor them but during the Fall, Winter and early Spring it's very complicated in Cook Inlet," said Manuel Castellote, who lead the project for NOAA Fisheries.

The acoustic monitors were placed on the ocean floor at 13 locations from Kachemak Bay and north into the Knik Arm.

"The first most surprising result was that we didn't expect to have so many whale detections in the upper part in the Northern part of Cook Inlet. Because the ice gets pretty intense, and all the previous knowledge from aerial surveys and other studies show that they disperse to the Southern end or mid inlet, but in our case we detected belugas almost on a daily basis, which was surprising," Castollete said. "Even in the arms, Knik Arm and Turnagain Arm they were coming in even in winter where tides and current combination with ice is a risky place to navigate, so we really don't know how they can cope with this environment."

Castellote says knowing the year-round presence of belugas in Upper Cook Inlet is useful for researchers because it is the area where the whales are exposed to the most disturbance by shipping traffic and other human activities.

"The other part that was interesting in our study is that foraging behavior seems to be focused in the Summer from Spring to Fall basically when there's more fish rungs going into rivers," Castellote said. "We still have no idea where and when do they feed outside of the summer period, which is a big piece of the puzzle to understand how we can support the conservation of these species."

Castellote says determining a new project is focused on determining where and what belugas feed on during the months outside of summer.

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