State, federal and tribal fish biologists hope to update on Monday the forecast of the spring chinook salmon run headed for the upper Columbia and Snake rivers.
The Columbia River Technical Advisory Committee met early this week and concluded there was not enough information available to make a reliable update, said Stuart Ellis of the Columbia River Inter-Tribal Fish Commission and TAC chairman.
A run of 160,400 spring chinook was forecast in December to enter the Columbia River this year. Through Tuesday, the count for the season at Bonneville Dam was 25,197 adult spring chinook. The 10-year average cumulative count through May 9 is 104,606.
The count at Bonneville Dam reached a daily peak of 6,177 adult spring chinook on Friday, then dropped to 4,342 on Saturday, 2,544 on Sunday, 1,651 on Monday and 1,234 on Tuesday.
Typically, when the Bonneville count hits a high, then starts to decline, that denotes the 50-percent passage mark and forecasting the run is possible.
But maybe not in 2017.
“A majority of the TAC thinks there is a good chance that the flows jumping way up impacted passage,’’ said Ellis. “They feel the decline is not reflective of the actual run.’’
Streamflow at Bonneville Dam jumped from 340,000 cubic feet per second on Thursday to 452,000 cubic feet per second on Tuesday. A year ago, the flow was 278,000 cubic feet per second at this time.
Ellis said streamflow is forecast to stay at 400,000 cubic feet per second at McNary Dam through the end of this week, then drop. But, he added, flow forecasts for more than a week out are not particularly reliable.
“It depends on the temperature,’’ Ellis said. “If it’s warm, the snow will melt and we could see it really high. If it stays relatively cool, it’ll just be pretty high. If the flows are stable, the fish will probably get back on it. If they change rapidly, it may make things confusing.’’
He said the chinook might wait another week or two to pass Bonneville, but are biologically programmed to get to their tributary streams before flows in the headwaters get too low to get there.
“They want to get into the high country,’’ Ellis said.
The biologists who are optimistic on the spring chinook run have several pieces of information to support their view.
Ellis said early-season test netting caught good numbers of spring chinook, as has research test fishing in Cathlamet Channel and research fishing by the National Marine Fisheries Service near the mouth of the Columbia as part of a sea lion predation study.
Ellis said a count of 93,400 at Bonneville Dam is needed to cover Endangered Species Act impacts already caught in the lower Columbia sport season that ended April 23, plus commercial fishing in off-channel locations like Youngs Bay.
There are multiple fishing decisions dependent on the updated spring chinook forecast.
“There’s increasing pressure to get this figured out,’’ he said.