Movement and Behavior of Juvenile Salmonids at Bonneville Dam, Columbia River

The Problem

At Bonneville Dam, past studies have shown that the current bypass systems do not divert sufficient numbers of fish away from the turbines. To understand why so few juvenile fish are bypassed at Bonneville Dam and to establish a baseline from which to improve, the U.S. Army Corps of Engineers (COE) initiated a monitoring and evaluation program. As part of that program, the USGS's Columbia

Aerial photo of Bonneville Dam looking downriver. Spillway is in the center with powerhouses on either shore. Image source: U.S. Army Corps of Engineers.

River Research Laboratory (CRRL) was contracted by the COE to evaluate behavior and passage of juvenile salmonids at Bonneville Dam. Personnel from CRRL utilized state-of-the-art radio telemetry techniques to conduct the first estimates of species-specific passage estimates for the entire Bonneville Dam project. In 2000, a relatively normal water year, passage through non-turbine routes (spill, bypass structures, etc) at Bonneville Dam was estimated to be between 73% and 91%, depending on species. However, during the low flows and resultant low spill levels encountered in 2001, passage through non-turbine routes ranged from 40-56%, depending on species. In response, the COE has initiated various programs aimed at improving passage through non-turbine routes. The COE field-tested a prototype screen system at Powerhouse 2 (north side of the river) in 2001 and 2002. In 2002, tests were also conducted at Powerhouse 1 on a new minimum gap runner turbine, designed to be less harmful to fish. The sluiceway at Powerhouse 1 will be evaluated in 2003 and 2004 to determine existing efficiency and survival. Also in 2004, a new Surface Flow Bypass Corner Collector will be evaluated at Powerhouse 2. The fish behavior and passage data the CRRL has collected at Bonneville Dam provide a valuable baseline for evaluating the performance of these and future management actions aimed at improving juvenile fish passage and survival.

Objectives

The objectives of the project are to: 1) determine the behavior, distribution, and approach patterns of fish in the forebay areas of Bonneville Dam, 2) determine the timing and route of dam passage of fish, 3) estimate passage through non-turbine routes for the entire Bonneville Dam complex, and 4) provide data to estimate survival of radio tagged fish released above Bonneville Dam.

Picture of juvenile salmon after being implanted with miniature radio transmitter.

Methodology

Thousands of yearling chinook salmon and steelhead and subyearling chinook salmon are radio-tagged annually at various locations upstream of Bonneville Dam. These fish are tagged and released with the run-at-large, usually from late April through May for yearlings and late June through July for subyearlings. Extensive aerial and underwater radio antenna arrays in and around Bonneville Dam provide continuous movement and passage data of radio-tagged fish. These data enable estimates of fish passage metrics such as fish passage efficiency, fish guidance efficiency, spill efficiency, spill effectiveness, and survival. The estimates can then be used as a measure of the performance of various management actions (e.g., dam operating conditions and structural modifications) to improve juvenile salmonid passage and survival.

Highlights and Key Findings

Radio telemetry data collected on juvenile salmonids during 2000-2002 indicates passage through non-turbine routes and other passage metrics can vary widely depending on flows and project operations. During 2000 and 2002, relatively normal water years, passage through non-turbine routes ranged from 73-91%, depending on species. Spillway efficiency, the proportion of all fish passing the project that passed through spill, ranged from 33-56% in 2000 and 2002, depending on species. However, during the low flows and resultant low spill levels (spillway efficiency ranged from 2-16%) encountered in 2001, passage through non-turbine routes ranged from only 40-56%, depending on species. Fish Guidance Efficiency (FGE), the proportion of fish that passed the powerhouse that were guided into the bypass system, did not appear to be affected by flow or spill. Regardless of year, spring migrants experienced FGEs of 50-75% at Powerhouse 1 and 37-59% at B2. Summer migrants experienced the lowest FGEs: 20-57% at Powerhouse 1 and 25-47% at Powerhouse 2. These results highlight the importance of spill in achieving high passage through non-turbine routes at Bonneville Dam under the current turbine bypass systems.

Where Are We Headed In 2003

We will use radio telemetry to evaluate survival through passage route-specific locations at Powerhouse 1 on a species by species basis in 2003. Radio-tagged yearling and subyearling chinook salmon will be released into the Downstream Salmonid Migrant Channel (DSM), Sluiceway, and Minimum Gap Runner (MGR) turbine unit 6 at Powerhouse 1. Numerous fixed-antenna sites downstream of Bonneville Dam will monitor these fish and the data will then be used to estimate relative survival. Completion of a Surface Flow Bypass Corner Collector at Powerhouse 2 is expected before the 2004 juvenile salmonid migration season. During 2004, we plan to evaluate the Corner Collector with radio telemetry and to continue project-wide radio telemetry monitoring.

Project Contact

Noah Adams
U.S. Geological Survey
Western Fisheries Research Center
Columbia River Research Laboratory
5501-A Cook-Underwood Rd.
Cook, WA 98605-9717

Email: noah_adams@usgs.gov
Phone: 509-538-2299
Fax: 509-538-2843

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