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How Fast Can a Salmon Swim Upstream to Idaho Waters? by Rich Landers Spokesman-Review, May 8, 2015

Answer: From Bonneville Dam, salmon take four to six weeks to travel to the Little Salmon River near Riggins, Idaho

FISHING -- How long it takes for salmon to travel from Bonneville Dam to Idaho?

Joe DuPont, Idaho Fish and Game regional fisheries manager in Lewiston looked at data and came up with answers to that often-asked question from curious anglers.

On average, an adult spring chinook takes about 18 days to swim 253 river miles from Bonneville Dam to Lower Granite dam, including passage over a total of four Columbia River dams and four more on the Snake River.

After crossing Lower Granite Dam, the salmon need another day or two up the Snake to reach Idaho, for a total of about 19-20 days in average flows, DuPont said.

This year, with lower than normal flows, spring chinook are making it faster to Idaho -- about 13 days.

Considering the fish counts at dams, "the majority of the chinook salmon destined for the Clearwater Region will all be in Idaho in two weeks," he said Tuesday.

Salmon River anglers wonder how long it takes their share of the Snake River salmon run to travel farther upstream, from Lower Granite Dam to Riggins.

This journey varies more widely depending upon flows and water clarity, DuPont said.

"When flows are high and dirty it can cause chinook to stop migrating. In fact there is evidence that the Slide Rapid in the lower Salmon River can greatly delay migrations in higher flows."

However, on a year like this, when river flows are low, the fish will get there fast, he said:

• 5-13 days to run 90 miles from the Idaho state line to Rice Creek Bridge.
• 7-20 days to run 135 miles from the Idaho state line to Little Salmon River.

Faster travel times tend to translate into slower fishing, he said.

"With these lower flows, fish are moving faster and more up the middle of the river making fishing more difficult," he said.

"Fish are already showing up at Kooskia Hatchery, and PIT tagged fish are passing the array in the lower South Fork Clearwater River. I suspect by next week we will have documented harvest all the way upstream to around Kooskia."