Survival Rates of Juvenile Salmonids Passing Through the Bonneville Dam and Spillway in 2008 [report]

Gene R. Ploskey, Mark A. Weiland, Derrek M. Faber, Zhiqun Deng, Gary E. Johnson, James S. Hughes, Shon A. Zimmerman, Tyrell J. Monter, Aaron W. Cushing, Matthew C. Wilberding, Robin E. Durham, R. L. Townsend (+7 others)
2009 unpublished
In 2008, the Portland District of the U.S. Army Corps of Engineers (USACE) contracted with the Pacific Northwest National Laboratory (PNNL) to conduct an acoustic telemetry study to estimate the survival rates of juvenile Chinook salmon and steelhead passing through Bonneville Dam (BON) and its spillway. Of particular interest was the relative survival rate of smolts detected passing through end spill bays 1-3 and 16-18, which had deep flow deflectors immediately downstream of spill gates,
more » ... s the survival rate of smolts passing through middle spill bays 4-15, which had shallow flow deflectors. Yearling Chinook salmon (YC), steelhead (STH), and fall Chinook salmon (FC) longer than 95 mm were collected from routine smolt monitoring samples at John Day Dam (JDA) and held overnight before surgery so that they were not overly stressed. Smolts longer than 95 mm were surgically implanted with Juvenile Acoustic Telemetry System (JSATS) and passive integrated transponder (PIT) tags and held another night to allow time for fish to recover from surgery. Fish tagged the previous day were released by a PNNL team three times per day (morning, midday, and night) in the JDA pool near Arlington, Oregon, and about 2.5 km below JDA in spring and summer. The team also released FC about 3 km below The Dalles Dam (TDA) in summer. Releases of live JSATS-tagged smolts in the Columbia River upstream of BON totaled 3431 YC and 3430 STH in spring. In summer, 5909 FC were released upstream of BON. Releases were spread out over 28 consecutive days (April 29 through May 27) during spring and over 29 consecutive days (June 15 through July 13) in summer. All of the "treatment" fish released above BON had the opportunity to be detected and regrouped by a BON forebay entrance array of autonomous nodes or by dam-face arrays at the BON spillway (this study) or BON Powerhouse 2 (B2) ) before they passed the BON project. An array is a group of underwater listening devices deployed to detect acoustic tags in fish passing through a forebay or an entire cross section of the river above or below a dam. Non-spillway passage routes were assigned based on detections of PIT tags in the B2 Corner Collector (B2CC) and B2 Juvenile Bypass System (B2 JBS) and acoustic detections on a cabled JSATS array in the B2 forebay (from Faber et al. 2009). Routes of spillway passage included end bays 1-3 and 16-18 with deep flow deflectors downstream of spill gates and middle bays 4-15 with shallow flow deflectors. Powerhouse 1 was not monitored. A National Marine Fisheries Service (NMFS) team released 826 live and 50 dead tagged YC in spring and 1020 live and 52 dead tagged FC smolts in summer into the downstream end of the BON tailrace near the USACE boat launch three times per day (about 0600, 1300, and 2100 hours PST) to serve as reference releases (controls) for virtual releases of treatment fish from upstream of the dam. Reference releases were made daily from April 30 through June 2 and from June 16 through July 22. The NMFS team also released 826 live YC and 1020 live FC smolts directly into the B2CC on the same days and at roughly the same times that fish were released in the tailrace. Pairing the B2CC-specific releases and tailwater releases provided a means of scaling paired-release estimates of dam-passage survival rates using a triple-release model (see Faber et al. 2009 ). The common tailwater that both treatment and reference releases of tagged smolts swam through was from the tailrace-release site 2 km downstream of the dam through three survival-detection arrays located about 31, 42, and 148 km downstream. Some treatment fish were detected by the forebay entrance array located about 2 km upstream of BON and classified as a virtual release of fish that passed through 2 to 3 km of forebay, the dam, 2.2 to 2.6 km of tailrace, and the common tailwater. Tagged smolts passing through the spillway were detected and tracked by a dense array of 36 hydrophones. Two hydrophones vi were mounted on each of 18 spillway piers south of spill bays at elevations 12.2 and 18.3 m above mean sea level (MSL). Smolts were tracked passing into specific spill bays and were classified as virtual releases of fish passing through end or middle spill bays. End and middle bay virtual releases were pooled to define a virtual release for the entire spillway. These virtual releases of spillway-passed smolts were exposed to passage through about 100 m of spillway forebay, spill bays, 2.2 km of tailrace, and the tailwater. In contrast to treatment fish, tailrace reference releases of fish experienced passage through the tailwater only and therefore were used as controls that did not pass the forebay, dam, or tailrace. Singlerelease, Cormack-Jolly-Seber (CJS) estimates of survival rates were calculated from detection histories on the three tailwater survival-detection arrays for each virtual or reference release of fish. Single-release survival estimates were for the river reach from the virtual or tailrace release sites to the primary detection array or from the primary array to the secondary array and included all mortality that occurred in the common tailwater. Paired-release survival estimates for dam-passed or spillway-passed fish to the tailrace-release site were calculated as the ratio of the survival rates of virtual releases of treatment fish to the survival rates of fish in tailrace reference releases. The paired-release estimate is designed to remove the mortality of fish that occurs in the common tailwater. Major Findings Detection performance of autonomous node arrays was best upstream of BON and generally decreased with the increasing distance of arrays downstream of the dam. An examination of tailwater egress rates revealed the following: 6. For most years and particularly years with above-average discharge, tagging at JDA should start by April 20 to be more representative of run timing at BON. The tagging schedule for 2008 did a good job representing run timing for STH and FC at BON and probably would not require alteration for a similar water year. xi
doi:10.2172/971109 fatcat:zbjvthrshzgonimrspomsia6zy