Seawatch: Late-stage chinooks not as safe as thought

Seawatch: Late-stage chinooks not as safe as thought

“It has been assumed that the early stage in the ocean is more dangerous”

Researchers at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences have made a discovery about mortality in late-stage chinook salmon — fish that have been in the marine environment for two years or more — that is a bit surprising.

The researchers, Andy Seitz and Michael Courtney, have been using pop-up satellite tags to study chinook salmon since 2013. A satellite tag is attached to a fish, where it collects data on temperature, depth and ambient light intensity. On a pre-programmed date, the tag releases from the fish, pops up to the surface of the ocean and transmits its stored data to satellites that researchers can access from a computer.

They were testing whether the tags are an effective tool for studying chinook salmon ecology and behavior.

ADVERTISEMENT
0 seconds of 0 secondsVolume 0%
Press shift question mark to access a list of keyboard shortcuts
00:00
00:00
00:00
 

“It has been assumed that the early stage in the ocean is more dangerous,” Seitz told UAF News, “and that fish become safer as they grow.”

The researchers tagged 43 late-stage chinook salmon between 2013 and 2017, and 35 of the tags transmitted data back to satellites. Marine predators, including warm-blooded salmon sharks, cold-blooded fish and marine mammals, consumed 19 of the 35 tagged fish.

The results suggest that late-stage marine chinook salmon may not be as safe as originally suspected.

These fish salmon are an under-studied group, and their decline in recent years has led to fishery closures and restrictions, especially in Cook Inlet.

Early in this project, a number of the tags were transmitting data sooner than expected. Each tag is programmed with an “abort mission!” sensor that is triggered when the tag is inactive for three days, telling the tag to automatically transmit data to satellites even if it’s before the programmed release date.

Seitz and Courtney had tagged big chinook salmon off the coast of Dutch Harbor in December, when temperatures in the Bering Sea are about 39 to 43 degrees. But in many of the prematurely transmitted datasets, the researchers noticed a sudden spike in temperatures days before the data was transmitted.

“The depth records of these tags were still moving up and down, sometimes down to 400 meters, and remaining at this 77-degree temperature,” Seitz said. “The only place that can happen is in the stomach of a warm-blooded salmon shark.”

After exiting a shark’s digestive system, the tag would pop to the surface and remain inactive, triggering data transmission.

Cristy Fry can be reached at realist468@gmail.com.


• Cristy Fry can be reached at realist468@gmail.com.


More in News

Kenai City Manager Terry Eubank speaks during Kenai’s State of the City presentation at the Kenai Chamber of Commerce and Visitor Center in Kenai, Alaska, on Wednesday, April 2, 2025. (Jake Dye/Peninsula Clarion)
Services, projects spotlighted at Kenai’s State of the City

Mayor Brian Gabriel and City Manager Terry Eubank delivered the seventh annual address.

The Homer Public Library. File photo
In wake of executive order, peninsula libraries, museums brace for funding losses

Trump’s March 14 executive order may dismantle the Institute of Museum and Library Services “to the maximum extent consistent with applicable law.”

Cracks split the siding outside of Soldotna High School on Tuesday, Sept. 27, 2022 in Soldotna, Alaska. (Ashlyn O’Hara/Peninsula Clarion)
SoHi siding, Hope roof repair projects move forward

The Soldotna project has been reduced from its original scope.

Jacob Caldwell, chief executive officer of Kenai Aviation, stands at the Kenai Aviation desk at the Kenai Municipal Airport on Thursday, Sept. 13, 2022, in Kenai, Alaska. (Jake Dye/Peninsula Clarion)
Kenai Aviation selected to provide air service to Seward

Scheduled flights between Seward and Anchorage will begin May 1.

Monte Roberts, left, and Greg Brush, right, raise their hands during an emergency meeting of the Kenai River Special Management Area Advisory Board’s guide committee at the Kenai Peninsula Region Office of Alaska State Parks near Soldotna, Alaska, on Feb. 25, 2025. (Jake Dye/Peninsula Clarion)
KRSMA board pushes back on new guide stipulations, calls for public process

Stipulations 32 and 40 were included in an updated list emailed to Kenai River guides.

KPBSD Board of Education member Patti Truesdell speaks during a town hall meeting hosted by three Kenai Peninsula legislators in the Kenai Peninsula Borough Assembly Chambers in Soldotna, Alaska, on Saturday, March 29, 2025. (Jake Dye/Peninsula Clarion)
Education hot topic at local legislative town hall

More than 100 people attended a three-hour meeting where 46 spoke.

The Soldotna Field House is seen on a sunny Monday, March 31, 2025, in Soldotna, Alaska. (Jake Dye/Peninsula Clarion)
Field house work session set for April 9

A grand opening for the facility is slated for Aug. 16.

HEX President and CEO John Hendrix is photographed at Furie’s central processing facility in Nikiski, Alaska, on Wednesday, July 10, 2024. (Jake Dye/Peninsula Clarion)
Furie announces new lease to use Hilcorp rig, will drill this spring

A jack-up rig is a mobile platform that can be transported and deployed in different areas.

The ORPC proposed American Tidal Energy Project site is located at East Forland, Cook Inlet, just north of Nikiski, Alaska. Photo provided by ORPC
Marine energy developer pursues Cook Inlet tidal project

ORPC recently filed a draft pilot license application for a tidal energy project site near Nikiski.

Most Read