2012 Spring Chinook Escapement to the Upper Basin of the Klickitat River Based on DIDSON Sonar Counts
A Dual-Frequency Identification Sonar (DIDSON) sonar was deployed to observe passage of fish through the Castile Falls fishway on the Klickitat River, to obtain an estimate of 2012 spring Chinook Oncorhynchus tshawytscha escapement to the upper basin. The DIDSON was set up to continuously record sequential 1-hour files from July 2 until September 21. A total of 30 observations of medium to large-sized fish, presumed to be spring Chinook, were observed outside the fishway swimming from in an upstream direction. This estimate is similar in magnitude to the escapement estimates of 24 ± 4, 26 to 27, and 38 derived with the DIDSON in 2009, 2010 and 2011, respectively. Also similar to prior years, the 2012 estimate is substantially higher than the estimate of 15 at based on spawning ground surveys (5 redds observed X 3 fish/redd).
Unlike prior years, a similar set of observations were recorded with a video camera recently installed in a newly constructed monitoring facility. The video recordings, showed 45 fish passage events in the corresponding July-September period – 50% more than observed with the DIDSON. Also, the video images indicated that the majority of fish were steelhead (34 of 45; 76%), as opposed to spring Chinook (11 of 45; 24%). A video count of 11 spring Chinook is not dissimilar to the estimate of 15 based on expanded redd counts. Assuming that the species mix was similar across years, we readjusted our prior estimates of spring Chinook escapement for the years 2009 to 2011, making the new estimates to be only 6, 6, and 9 in 2009, 2010 and 2011, respectively. Similar to 2012, these lower estimates bring them closer in line with escapement estimates based on expanded redd counts for these years. However, these new estimates also indicate that spring Chinook are recolonizing the upper basin at a much lower rate than previously thought. Steelhead escapement in prior years was estimated as 18, 20 to 21 and 9 for 2009, 2010 and 2011, respectively.
Galbreath, P.F., P.E. Barber, and C.R. Frederiksen. 2013. 2012 Spring Chinook escapement to the upper basin of the Klickitat River based on DIDSON sonar counts. Columbia River Inter-Tribal Fish Commission Technical Report 13-06, Portland, Oregon.