Last month, the Alaska Department of Fish and Game and the US Fish and Wildlife Service conducted fieldwork for the first phase of a project that marks coho salmon and tracks their movement via radio signals. Scientists want to better understand their spatial distribution, including where they swim, how they get there and where they spawn.
Ken Gates is a senior fish biologist with the US Fish and Wildlife. He says the tracking method, known as radio telemetry, is a common practice among biologists.
“Knowing where the fish are through this technology can help us prioritize where we spend our money,” he said.
Gates says the project informs scientists about how the Kenai River fishery is being used and what enhancement efforts, such as fish passage channels, are needed in the future.
“One of the biggest takeaways for me would be the future of where this project could lead,” said Johnna Elkins, a fisheries biologist with the Alaska Department of Fish and Game. She managed the day-to-day operations of the project in the field.
Since fieldwork began in 2022, the agencies have collectively tagged about 1,300 coho on the Kenai River between the Kenai River Bridge in Soldotna and Bear Creek, about a mile downstream from the confluence of the Funny River . The tags themselves are small, programmed to emit signals 24 hours a day for 240 days. They are inserted into the coho’s stomach through the mouth with an antenna sticking out.
During the late summer and early fall, scientists were on the river every day of the week netting and tagging coho. Gates, who was not in the field, says the team also tracks tagged coho twice a week by boat, air or foot.
“We have to physically go out every week to track these fish with radio receivers that decode the radio frequency coming off the tag,” Gates said. “We have specialized equipment that is tuned for a certain frequency range.”
Scientists say some of the radio tags were traced to coho that later died, or had been archived. The tags had a phone number marked on them in case a fisherman found one. They say that this season, about 30 of the nearly 450 disposed have been called.
Although there have been some less complete studies that have tracked the movement of the coho of the Kenai River, scientists say that there are still many unknowns about their behavior. So far, new data from this sample size dispelled a myth that coho courses can occur at the beginning of winter. The team didn’t catch much after mid-October.
Gates says the team also found that tributary bank coho entered the river before those spawned in the main stem.
“The Kenai River, for whatever reason, is very unique compared to other watersheds across the state,” Gates said. “The stream life of some species, of coho in particular, we’re talking about months that these fish will stay in fresh water before they really start spawning.”
While the study’s sample size is small, scientists say the tagging project allows them to better estimate the size of the coho population in the Kenai River basin.
“The collaborative work has been great, I think it’s great to work with multi-agency to improve fisheries,” Elkins said. “And also, just develop future projects on the coho.”
If funding is approved, the second phase of the project would tag Kenai River Coho to confirm their genetic basis from the first date. Scientists are also adding known populations of coho in the watershed to a database.