Survival of Juvenile Chinook Salmon Passing the Bonneville Dam Spillway in 2007

Abstract

Executive SummaryIn 2007, the Portland District of the U.S. Army Corps of Engineers contracted with the Pacific Northwest National Laboratory (PNNL) to conduct an acoustic telemetry study to estimate the survival of juvenile Chinook salmon passing the spillway at Bonneville Dam. Fish longer than 95 mm were surgically implanted with Juvenile Acoustic Telemetry System (JSATS) and passive integrated transponder (PIT) tags, held overnight in tanks supplied with continuous flow of river water to allow time for recovery from surgery, and released between 1400 and 1700 hours on 16 days in spring and 14 days in summer. Some fish were released in the spillway forebay above the dam to create treatment-release groups that would pass through the spillway, and other fish were released 2 km downstream of the spillway in the tailrace to create reference-release groups that did not pass through the spillway. Reference releases in the tailrace began about 1 hour after the start of treatment releases in the forebay so that both groups would mix and pass through the common downstream tailwater about the same time of day. The common tailwater for our survival estimates was from the tailrace-release site 2 km downstream of the dam to the first or second of three tag-detection arrays located downstream of the dam. An array is a group of autonomous underwater receivers (nodes) deployed to listen for acoustic tags passing through an entire cross section of the river. Treatment fish were exposed to passage through < 76 m of spillway forebay, spill bays, and 2 km of tailrace that the reference-release groups avoided. Single-release estimates included survival from the point of release to the primary detection array or from the primary array to the secondary array and included losses of fish in the common tailwater. Paired-release survival estimates for spillway-passed fish to the tailrace-release site were calculated as the ratio of the survivals of treatment-release groups to the survivals of paired reference-release groups to remove effects of losses of fish in the common tailwater. The PNNL team released treatment fish in the forebay and a National Oceanic and Atmospheric Administration Fisheries team released reference fish in the tailrace. Some treatment fish were detected by spillway hydrophones and assigned a bay of passage based upon the location of the last of at least four detections of implanted acoustic tags. Detections of PIT tags in the Powerhouse 2 (B2) Corner Collector (B2CC) and B2 Juvenile Bypass System (B2 JBS) were used to assign non-spillway routes of passage. Major FindingsWe only tagged fish longer than 95 mm to avoid overburdening small fish and inducing unnecessary tag effects. This 95-mm minimum length for tagging did not restrict the lengths of fish that could be tagged in spring because the length of almost all yearlings exceeded 95 mm, and the frequencies of tagged and untagged yearling Chinook salmon in the JBS samples being of similar length were very similar. In contrast, the 95-mm minimum length to be el...

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

“…Observing slower egress rates for FC through middle spill bays (Point 6 above) is consistent with findings in 2007. In 2007 found that the mean travel time from spillway passage to an egress array located 9 km downstream of the dam was 20 minutes longer (P = 0.0105) for fish passing 4.5 through middle bays (2.58 hours) than it was for fish passing through end bays (2.26 hours).…”

“…Previous experience indicates that dead fish usually travel much slower than live fish because they typically sink for a few days before they float and travel at the speed of prevailing river currents (Counihan et al 2006a(Counihan et al , 2006bPloskey et al 2008). The tendency of dead fish to travel slower than live fish led Counihan et al (2006a) to exclude data for fish with long egress times (>99.7 percentile) from survival calculations.…”

Acoustic Telemetry Evaluation of Juvenile Salmonid Passage and Survival at John Day Dam with Emphasis on the Prototype Surface Flow Outlet, 2008

“…In 2006, the JSATS receivers were deployed at various locations between John Day Dam and Camas, Washington (a 150-km reach of the river), to estimate turbine passage and tailwater survival rates at John Day Dam, and dam-passage and tailwater-passage survival rates for The Dalles Dam and Bonneville Dam (Ploskey et al 2007). The first deployment of the JSATS cabled system was in 2007 at the Bonneville spillway to estimate route-specific passage and survival rates (Ploskey et al 2008). …”

“…Several filtering algorithms were then applied to the raw results from the decoding utilities to exclude spurious data and false positives. Tag-detection data from JSATS autonomous nodes were processed by two independent groups as a quality-control measure as in previous studies (Ploskey et al 2007;Ploskey et al 2008) using standardized methods. One method processed data using programs written in Python, and the other involved processing data with programs written in the Statistical Analysis System (SAS).…”

“…The >95-mm-length requirement on candidate fish for tagging did not restrict the lengths of fish that could be tagged in the spring and only excluded about 9% of the run-of-river subyearlings from tagging in 2008 (Figure 4.1). In 2007, 40% of subyearlings could not be tagged because they were too small (Ploskey et al 2008), presumably because growth was slower that year. Tagging must include 80-to 95-mm smolts to be fully representative of the run-of-river population in summer, but only the production of smaller lighter tags than those available in 2008 will make that possible.…”