Jan 14, 2014: The Northwest Fisheries Science Center has completed its analysis of 2013 survival for juvenile Snake River chinook and steelhead through the eight dams and reservoirs on the lower Snake and Columbia rivers. See the report here.
The survival rate for spring chinook was 52.5 percent, equivalent to the long-term average survival for this species.
Steelhead survival for the same reach was estimated at 50.1 percent, also similar to the long-term average, but relatively low compared to recent years. NWFSC noted that steelhead survival between Lower Granite and McNary Dams decreased through the last few weeks of the season, possibly due to increased predation and increasing temperatures during that period.
Other facts that NWFSC noted:
q Flows on the rivers were below average. Spring flow in the Snake River was the fifth lowest in the past 21 years.
q Water temperatures were higher than average.
q Surface passage and spill continue to promote faster fish travel times through the dams and reservoirs.
q Spill percentage was higher than average.
q Survival was unusually low in the pool behind Lower Granite Dam.
q The estimated percentage of fish transported was among the lowest known estimates over the past 20 years.