Acoustic Imaging Evaluation of Juvenile Salmonid Behavior in the Immediate Forebay of the Water Temperature Control Tower at Cougar Dam, 2010

Abstract

Executive SummaryThis report presents the results of an evaluation of juvenile Chinook salmon (Oncorhynchus tshawytscha) behavior at Cougar Dam (CGR) on the south fork of the McKenzie River in Oregon in 2010. The study was conducted by the Pacific Northwest National Laboratory (PNNL) for the U.S. Army Corps of Engineers, Portland District (USACE). The overall goal of the study was to characterize juvenile salmonid behavior and movement patterns in the immediate forebay of the Water Temperature Control (WTC) tower of the dam for USACE and fisheries resource managers use in making decisions about bioengineering designs for long-term structures and/or operations to facilitate safe downstream passage for juvenile salmonids.We collected acoustic imaging (Dual-Frequency Identification Sonar; DIDSON) data from March 1, 2010, through January 31, 2011, to evaluate juvenile salmonid behavior year-round in the immediate forebay surface layer of the WTC tower (within 20 m, depth 0 to 5 m). From October 28, 2010, through January 31, 2011, a BlueView acoustic camera also was deployed in an attempt to determine its usefulness for future studies and to augment the DIDSON data. A total of 277 days of DIDSON and 65 days of BlueView data were collected during the study period. Because of the large amount of data recorded by the acoustic cameras each day and the cost for analysis, it was not feasible to analyze all of the acquired data. Instead, in consultation with USACE personnel, we processed a total of 45 separate 24-hour periods of DIDSON data covering every month throughout the 11-month study; some months included more sub-sampled days than others to cover special circumstances, such as, different forebay elevations and the presence of large numbers of juvenile fish. Two different 24-hour periods were processed for the BlueView data for the feasibility study. A basic observation of fish, that is, a single fish or a school of fish, in the sample volume was termed an "event." The data were analyzed to characterize a fish abundance index, fish size patterns, movement direction, diel and seasonal behavior patterns, schooling, and predation.Juvenile salmonids were present in the immediate forebay of the WTC tower throughout the study (March 2010 through January 2011). The juvenile salmonid (hereafter, called "fish" unless otherwise noted) abundance index was low in early spring (<200 fish per sample-day), began to increase in late April, and peaked on May 19 (6,039 fish). A second peak was observed on June 6 (2904 fish). Screwtrap estimates obtained from the Oregon Department of Fish and Wildlife (ODFW) of juvenile Chinook caught in the tailrace of the dam show comparable numbers, with estimates increasing in the spring and peaking in early June (~2400 fish). The fish abundance index began to decrease in early June and remained low in the summer months (<100 fish per sample-day). During the fall and winter, fish numbers per subsample date varied with a peak on November 10 (1881 fish) and a minimum on December 7 (12 fish). A second...

Hydroacoustic Estimates of Fish Density Distributions in Cougar Reservoir, 2011

“…Most fish were detected in the upper 6 m of the water column and none were detected deeper than about 36 m. These observations contrast with those of Khan et al (2012), who reported most fish within 50 m of the water control tower detected at depths between 10 and 20 m during two dates (11/14 and 12/07/2011) when they sampled vertical distributions with a BlueView acoustic camera. Khan et al (2012) observed few fish in the upper 10 m of the water column near the tower. We can only assume that the depth distribution near the tower was unique and highly influenced by the flow regime there.…”

“…The 2010 screw-trap data collected by ODFW indicated that juvenile Chinook salmon pass through the dam all year, and preliminary estimates indicate that higher numbers (perhaps several thousands of fish per month) pass downstream in winter (Figure 3.5 in Khan et al 2012). The 2011 screw-trap catches follow a similar pattern but were not expanded to abundance estimates by ODFW (Figure 14 in Romer et al 2012).…”

“…The rafts were less of an impediment than the many signal cables running between the rafts. In 2010, Khan et al (2012) reported observing numerous schools of fish within 50 m of the tower from April through June. Schooling behavior was not observed in fall or winter, even though the total number of fish detection events was higher in fall than it was in summer (Khan et al 2012).…”

“…In 2010, Khan et al (2012) reported observing numerous schools of fish within 50 m of the tower from April through June. Schooling behavior was not observed in fall or winter, even though the total number of fish detection events was higher in fall than it was in summer (Khan et al 2012). In contrast, we observed no evidence of fish schooling during any survey in 2011, but again, we could not sample near the tower where milling of fish was the most common behavior observed in 2010.…”

Predator and prey events at the entrance of a surface‐oriented fish collector at North Fork Dam, Oregon

“…Factors influencing the performance of surface collectors are generally defined in physical or hydrological metrics without incorporating predator fish assemblage data into physical or performance evaluation design. The facilities at North Fork Dam and Reservoir, along with other surface‐oriented fish collectors, are known to have predator‐size fish (including Salvelinus confluentus and other sport fishes) in close proximity to their entrances (Beeman et al., 2016b; Khan et al., 2012; McIlvaine, 2015). Given the relatively short time the FSC was monitored, little is known about the contribution of Salvelinus confluentus and other sport fishes to higher mortality rates of smolt‐size fish upstream of dams.…”