ARIEL, Wash. — The transport of adult coho salmon to the North Fork of the Lewis River upstream of Swift Dam will be reduced about 20 percent this fall.
The Lewis River Aquatic Coordination Committee agreed last week to cut the trucking of coho from the lower Lewis from 9,000 spawners to 7,500, and also to add late-stock coho to the reintroduction effort.
The committee is composed of PacifiCorp, the state and federal fishery agencies, the U.S. Forest Service, Indian tribes, Cowlitz PUD, conservation groups and others who signed the settlement agreement as part of the relicensing of Merwin, Yale and Swift hydroelectric dams.
PacifiCorp’s 50-year federal license to operate the three Lewis River dams calls for reintroduction of spring chinook, coho and winter steelhead upstream of Swift.
Biologist Erik Lesko of PacifiCorp said the determination to transport 9,000 coho relied largely on opinion from local biologists and the Forest Service.
However, 9,000 coho may be more than the carrying capacity base on more recent evaluations of spawning success upstream of Swift Dam, he said.
Many of the coho in past years have stayed near the release site just upstream of Eagle Cliff Bridge and not distributed well throughout the upper North Lewis watershed, Lesko added.
Streamflow in the North Fork of the Lewis is very low this year. Low flows reduce available habitat for side channel and tributary spawners such as coho.
PacifiCorp is developing protocols for releasing fish higher in the basin, plus in tributaries such as Clear Creek, Crab Creek and the Muddy River.
The settlement agreement calls for the transport only of early-stock coho. Early coho enter the Columbia in August and September. Their time in the ocean is mostly south of the Columbia River. Late coho return in October, November and even December. Their ocean residency is off the coasts of Washington and British Columbia.
The Lower Columbia River Endangered Species Act Recovery Plan does not differentiate between early and late stocks, but considers coho as one stock.
Using the returns of natural-origin coho at the Merwin Dam fish trap as a guide, PacifiCorp has developed a schedule of coho transport upstream of Swift that starts with 300 fish in early September and concludes with 600 coho the final two weeks of December.
Sixty-four percent of the coho transport would be in September and October, with 36 percent in November and December.
Biologist Jim Byrne of the Washington Department of Fish and Wildlife asked if adding late coho to the upper watershed creates a greater likelihood the coho will damage spawning nests of bull trout, also a threatened species.
“We all realize it’s a risk, and these risks would be present in the absence of dams,” Lesko said.
Eric Kinne, hatchery reform coordinator for the Department of Fish and Wildlife, said hopefully spreading coho out better in the watershed will lessen their spawning in the few spots used by bull trout.
Frank Shrier, principal scientist for PacifiCorp, also that with the water level at Swift Reservoir lowered due to the drought good spawning habitat for coho is showing near Eagle Cliff Bridge and at the mouth of Drift Creek.
When the reservoir is raised again in late fall or winter, those stretches could be inundated and the eggs would die before the young fish emerge from the gravel in January or February.
Some coho released each year at Eagle Cliff actually go down Swift Reservoir and use small tributaries such as Diamond Creek.
In-season modifications may be made based on coho returns and weather conditions this fall. Committee members agreed to discuss the situation again in mid-September.
