Warm water temperatures in the lower Snake River have put the brakes on the summer steelhead run.
“The fish aren’t entering the Snake River,” said Alan Byrne, a fisheries biologist for the Idaho Department of Fish and Game at Boise. “It seems like we have a thermal block.”
It is not uncommon for the run to stall when there is more than a few degrees of difference in water temperatures in the Snake and Columbia rivers. Water in the Columbia near McNary Dam has fluctuated between 65 and 66 degrees since July 20. During the same time frame, water near Ice Harbor Dam on the Snake River has been 70 degrees or slightly higher.
Byrne noted that for nearly two weeks, fewer than 100 steelhead per day have been counted in the fish ladder at Ice Harbor. At McNary, the daily counts have been between 700 and 1,900.
“We have seen this before. We have a hot year, the Snake River gets pretty hot and the steelhead just are not coming in because the Columbia is cooler,” Byrne said. “We think what is happening is the fish bound for Idaho are just waiting for the Snake River to cool down.”
He still expects fishing to be good.
A group of salmon and steelhead managers in the Columbia Basin is predicting 311,800 A-run steelhead and 52,800 B-run steelhead will return at least as far as Bonneville Dam. Last year, 318,000 of the smaller A-run steelhead and 37,000 of the large B-run steelhead were counted at Bonneville. So anglers can expect slightly fewer A-run fish and more of the coveted B-run.
Byrne said about 50 percent of A-run fish, or 156,000, predicted to pass Bonneville should make it past Lower Granite Dam, and 70 percent of the B-run steelhead, or 37,000, should return at least as far as Granite.
That totals about 194,000 steelhead at Granite.
A short section of the lower Clearwater River from its mouth to Memorial Bridge at Lewiston opened to catch-and-keep fishing Wednesday. The rest of the river has been open to catch-and-release fishing since July 1.
The Snake River opens to catch-and-keep fishing Sept. 1.
Through Tuesday, 1,310 steelhead had been counted passing Lower Granite Dam since June 1. The 10-year average is 3,827.