W-136-3
Drought, Stream Flow, Adult Chinook Salmon Migration, and Smolt Production within the Redwood Creek Basin
We used three smolt traps, two DIDSON sonar cameras, and two USGS stream gages within the Redwood Creek (RC) basin to assess effects of drought in WY’s 2013 and 2014 on adult Chinook salmon migration and smolt yield. Daily stream flows in WY 2013 during the adult migration were 15% and 9% below average in lower and upper RC, respectively. In WY 2014, average daily stream flows at both locations during the adult migration were 93% less than average. Adult Chinook salmon escapement to lower RC in 2012/13 equaled 3,401 with a resulting basin-wide smolt output of 663,676 or 195 smolts/adult. Smolt output from mid-upper RC in 2013 was the highest of record, and equaled 680,747. In 2013/14, 3,487 adult Chinook salmon entered lower RC, but only 84 adults migrated upstream into mid-upper RC. Smolt output from mid-upper RC (41 smolts per adult) was 99% less than output in 2013. Smolt output through lower RC in 2014 equaled 2224,184, or 64 smolts/adult. Drought flows in 2014 apparently decreased year-to-year smolt yield per adult by 67%.