Colville Tribes Fish and Wildlife release tagged Chinook below Chief Joseph Dam

BRIDGEPORT – The last of about 775 tagged juvenile Chinook salmon were released in the Columbia River below Chief Joseph Dam last Friday, May 6, by Colville Tribes Fish and Wildlife personnel, as part of its Phase II Implementation Plan. The last load included about 75 fish fitted with PIT (Passive Integrated Responder) or acoustic tags to allow researchers track the salmon on their journey through the dams, to the ocean, and back. 

The releases started in mid-March when the first salmon released at sites on Hangman Creek where that stream enters the Spokane River and at Kettle Falls. Similar releases continued downstream at Sand Point, and Grand Coulee through the reservoir reaches ending below Chief Joseph.

“We are releasing below Chief Joe Dam because we have already released above the dam,” said research scientist Casey Baldwin. “When they come through the dam we can compare their survival through the next downstream site. The difference in that survival will be the effect of going through the dams.”

The differences between PIT and acoustic tags include expense, duration, range, and detection. Because they are battery powered and miniaturized for use in salmon the acoustic tags are magnitudes more expensive to use that the barcode PIT tags. Every tagged salmon has a PIT inserted but far fewer also wear the acoustic type.

Each acoustic tag has power for about 75 days and emits a unique signal that pings every five seconds and can be detected for a couple hundred yards by underwater sensors. Arrays of hydrophones and receivers are placed underwater along the migration route to monitor fish movements. The hydrophone detects the signals and the receiver determines which fish is transmitting based on the code.

“We have six receivers set up on Chief Joe Dam.” said Baldwin. “Two on the spillway and four across the powerhouse.”

The tags allow researchers how the fish approach dam, where they pass through the dam, and the survival rate.

The non-battery PIT tags last for the life of the fish and must be read by a scanner when the fish passes close to it such as when navigating a fish ladder. PIT tags allow researchers to monitor returning salmon from their four-year period in the ocean.

Baldwin said the sample releases from this year’s tag study will probably not have a sufficient survival return rate for researchers to draw many conclusions. A larger release is planned for next year that will involve sufficient numbers of tagged fish to measure survivability and other factors.

In August 2019 tribal members released the first 30 adult Chinook in Lake Rufus Woods to return to their native Upper Columbia waters in eight decades. It was the beginning if an ambitious phased implementation of salmon above the dams and continues with the tagging and tracking release last week.