Weak salmon returns this fall to the North Fork of the Lewis River may slow efforts to restore coho upstream of Swift Dam.
PacifiCorp, along with the state and federal natural resource agencies, hopes to transport 7,500 coho from downstream of Merwin Dam to various points upstream of Swift Dam as part of the utility’s 30-year federal license to operate the three hydroelectric dams on the Lewis River.
A schedule was developed calling for the transport of 300 to 2,000 coho above Swift every 14 days, mimicking the timing of native Lewis River fish.
Through today, the schedule called for 2,800 early-stock coho to have been hauled, while the actual number is closer to 400, said Chris Karchesky, fish passage coordinator for PacifiCorp.
That’s because early-stock coho returns to the Lewis River are “a pretty dramatic no-show,’’ said Aaron Roberts, manager of several Southwest Washington hatcheries for the state Department of Fish and Wildlife.
The initial forecast called for a return of 16,000 early coho, but the number as of Monday was 3,510.
Transport of coho upstream of Swift Dam was put on hiatus in September and early October to allow the hatcheries to collect fish for spawning this fall.
Members of the Lewis River Aquatic Coordination Committee agreed two weeks ago not to backfill a shortage of early coho with late coho, which return to the river from mid-October into December.
The transport of late coho will follow the original schedule — if enough salmon are available.
Roberts said the initial forecast calls for 13,600 late coho back to the North Fork of the Lewis.
Historically, late coho returns have matched well with pre-season forecasts, Roberts said.
Early coho tend to migrate south of the Columbia River mouth. This year, there is a huge blob of warmer-than-normal water in the Pacific Ocean.
Late coho tend to migrate north of the Columbia River mouth.
“These late coho are north-turning fish,’’ Roberts said. “I think they will tell us a lot about ocean conditions.’’
A year ago, 9,000 coho — all early stock — were released in the upper watershed. Members of the Aquatic Coordination Committee agreed to cut that number to 7,500 coho, largely due to the fish tending to congregate in the Eagle Cliff-Muddy River mouth reach of the North Fork Lewis River rather than distributing widely.
Patrick Frazier of the Lower Columbia Fish Recovery Board said the congregation of coho near Eagle Cliff resulted in fish spawning on top of the nests of others and in predation of bull trout, a threatened species.
This year, the release of adult coho is being spread out between four sites — Eagle Cliff, Clear Creek, Muddy River and near Lower Falls — to get a better distribution of fish.
Frazier said falling short of the goal of 7,500 coho is not a major setback.
“If we don’t hit 7,500, it’s early in the reintroduction,’’ he said. “There’s not a huge urgency to get every single fish up there.’’
