UI study tracks salmon in Columbia

A spring chinook salmon tagged with a University of Idaho radio-tracking device was caught earlier this month at Cedar Creek Hole on the Lewis River in southwest Washington.

The 10-pound salmon with a clipped adipose fin was taken with a combination salmon egg-shrimp bait on July 4 by Vancouver fisherman Terry Prager just below Washington state’s sprawling salmon hatchery in Cowlitz County about eight miles upstream from the Columbia River. Based on the darkened color of the fish’s skin, it was clear that the salmon had been swimming in fresh water for weeks. The clipped fin showed it was a hatchery fish, and thus, legal to harvest.

Inside its gullet was a small radio telemetry device with a transmitter wire protruding from its mouth. The transmitter was marked to identify it as part of UI’s fishery research program. For the lucky fisherman, the device offered a $25 reward for its return.

Prager’s daughter, Elizabeth, was curious about what appeared to be a mystery: an Idaho-tagged fish swimming in Washington state waters.

She contacted Dan Joosten, a senior scientific aid working with the Cooperative Fish and Wildlife Research Unit, a multi-agency effort based at the university. She also mailed the transmitter back to researchers.

Joosten said the fish was trapped earlier this year just below Bonneville Dam. He said a team of researchers is studying how efforts to reduce sea lion predation of spring salmon at the dam are affecting fish migration. The fish are caught, “fed” transmitters and then released about 10 kilometers downstream, he said.

Receivers at the dam then track the fish’s movements as they return to the dam and climb its fish ladders. Joosten works under assistant Professor Chris Peery, the principal investigator on the study.

For some reason, the fish reversed course and swam nearly 60 miles back down the Columbia and turned up the Lewis River near Woodland, Wash. From there, it made its way to the hatchery area just above Cedar Creek.

Joosten said the fish could have been an upriver-bound salmon that strayed and failed to migrate to its home waters, or it was a Lewis River fish that strayed to Bonneville Dam and then returned to its home waters after being trapped and given the transmitter. Straying is part of the salmon’s natural diversity.