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Acoustic tagging seeks answers to King salmon decline

An ambitious new research project is aiming to better understand the lives of king salmon by focusing on their difficult journey from freshwater habitat to the ocean.

The project, a collaboration between the University of �Ӱ�ԭ�� Fairbanks and �Ӱ�ԭ�� Department of Fish and Game, is using hundreds of acoustic tags and an array of underwater hydrophones to track young salmon as they navigate the Kenai River to Cook Inlet.

Researchers are focusing on kings in the smolt stage, a relatively understudied period of development. Resources for studying king salmon have largely focused on adult fish.

The project comes amid widespread declines among �Ӱ�ԭ�� king salmon populations, and the Kenai River’s famous run has become the “poster child” for the struggles of the species, said Andy Seitz, a professor at the UAF College of Fisheries and Ocean Sciences. Knowing more about the perils facing juvenile salmon could spotlight the challenges they are facing.

“It’s a time when they’re going through physiological changes, and it’s also a dangerous stage,” said Seitz, who is co-leader of the project. “They’re changing from freshwater to saltwater fish, and there are a lot of hungry mouths in the ocean.”

A research team recently concluded the first season for the project by implanting 289 Kenai River king salmon smolt with tiny devices about the size of a Tic Tac mint that emit regular pings. Each has a unique signal, allowing researchers to identify individual fish with underwater hydrophones as they make their journey in the Kenai River to Cook Inlet.

The most notable array of sensors is a roughly 4-mile-wide span near the mouth of the Kenai, which researchers plan to double in size next year. It will monitor tagged fish during a critical stage when they depart their freshwater habitat.

The acoustic technology has never been used on juvenile salmon in �Ӱ�ԭ��, and the first summer was spent working to adapt it to the rugged Kenai River environment. CFOS students working on the tagging project include Johnna Elkins, Dakota Rygh and Danielle Tryon. Elkins and Tryon are also ADFG employees.

The project will expand in scope as it continues for each of the next two summers.

A better understanding of the survival bottlenecks facing young salmon could ultimately affect how they are managed in �Ӱ�ԭ�� rivers, said Tony Eskelin, a Soldotna-based fisheries biologist who is leading the project for ADFG.

“Transitioning into the marine environment is a perilous life stage for these fish,” he said. “If we can better understand factors affecting their survival, maybe we can make some decisions to help them along the way.”

“We have a lot of excitement for this project, and a lot of data to process.”

The project is being funded by a $4 million federal earmark through NOAA to research juvenile Chinook salmon.

ADDITIONAL CONTACTS: Andy Seitz, acseitz@alaska.edu; Tony Eskelin, anthony.eskelin@alaska.gov

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