CLACKAMAS, Ore. – The Oregon Department of Fish and Wildlife will be placing radio tags in coho salmon bound for the upper Willamette River and its tributaries over the next three weeks in an attempt to better understand the movements of fish returning to the basin.
ODFW staff will place 130 tags in coho captured at ODFW’s fish monitoring station at Willamette Falls. The tags will transmit signals to receivers stationed at the mouths of various rivers, allowing biologists to track the fish as they move upstream to spawn. Project managers hope the information collected from the study will help identify how coho move in the mainstem Willamette, and where they hold prior to moving up the tributaries to spawn later in fall.
Interest in the study was fueled in part by this year’s return of coho, which is predicted to develop into the largest on record in the upper Willamette. Fishery managers believe that by late October the numbers will exceed the previous high of 17,900 adults counted in 1970.
What is more remarkable than the sheer number of fish is the type of coho that are returning to the upper Willamette. These coho are predominately fish produced by natural spawning in the wild in tributary rivers like the Tualatin, Molalla, Pudding, Yamhill and Santiam. The last time ODFW saw the kinds of numbers it is seeing this year, the department was releasing approximately 10 million hatchery fish into the system primarily to support commercial and sport fisheries in the ocean and Columbia River. That practice ended in 1998 with a small release of hatchery coho into the Tualatin River.
“The upper Willamette is emerging as a very significant producer of naturally produced coho, which has important relevance to the ecology of the watershed and management of coho and other fish populations,” said Tom Murtagh, district fish biologist for ODFW’s Upper Willamette Watershed. “It’s a fascinating lesson in the population dynamics of coho salmon, and we want to get a better understanding of behavioral traits and habitat factors that are allowing this population to succeed.”
This is a cooperative effort being conducted by several interested partners. The tags that will be used in the study are being donated by the Confederated Tribes of the Grande Ronde and Eugene Watershed Enhancement Board. Technical assistance is being provided by Portland General Electric.
Anglers who catch a radio-tagged fish are asked to release the fish back into the wild unharmed. Anglers should be aware that each fish carrying a radio tag will also have a colored “floy” or “spaghetti” type tag in its back near the dorsal fin for identification. These tags are about 3 inches long and will be obvious to the angler.
For more information, contact Tom Murtagh at 
971-673-6044
.
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