Evaluation of Fish Behavior with Acoustic
Telemetry Relative to Prototype Passage Systems at
Lower Granite Dam

The Problem

The U.S. Army Corps of Engineers (USACE) has been evaluating the recovery of anadromous fish under the National Marine Fisheries Service's Biological

Figure 1. Lower Granite Dam with fish passage structures upstream of the powerhouse (2002).

Opinion. Surface bypass is one option being tested by the USACE to improve juvenile salmonid survival. Observations at several Columbia River dams have shown that migrating fish use shallow water passage structures, deep turbine or spillway routes for dam passage. In 1996, the USACE installed a prototype surface bypass collector (SBC) at Lower Granite Dam. Testing of a prototype surface bypass collector at Lower Granite Dam was completed in 2000. Radio telemetry and hydro-acoustic evaluations indicated that juvenile salmonid migrants used the SBC (Figure 1).

A behavioral guidance structure (BGS) was added to Lower Granite Dam in 1998. The purpose of the BGS was to divert fish away from the turbine intakes and allow greater opportunity for juvenile salmonids to find the SBC's entrances. The BGS diverted 61-92% of radio-tagged fish. During 2000, studies were designed to test the effects of powerhouse operations on SBC performance. As a result, the USACE installed a removable spillway weir (RSW) to improve surface bypass at Lower Granite Dam in 2002. Based on the surface bypass concept, the RSW discharges water at a much shallower depth than conventional spill bays. The goal of the RSW is to provide an alternative route of passage other than the turbines, provide more efficient spill (i.e., pass more fish with less water), and decrease the delay in migration time caused by dam passage. Preliminary results conducted on the RSW in 2002 indicate that the RSW may provide the best surface-oriented passage route for juvenile salmonid migrants tested to date. The USACE will be conducting further tests of RSW performance at Lower Granite Dam in 2003.

Objectives

The goal of this study is to assess how fish migration behavior is influenced by the RSW. The approach path that the fish take at the dam should be improved due a change in the hydraulic environment (i.e., flow variables) caused by the RSW. As testing continues, it will be vital to understand why the RSW works in order to incorporate the same concepts in future designs of surface bypass structures. The first objective of this study is to evaluate fine-scale, species-specific fish behavior immediately upstream of the RSW using a three dimensional fish tracking system. The second objective is to integrate fine-scale behavioral information from juvenile salmonid migrants with water velocity data generated at the dam and from flow modeling.

Methodology

The ultrasonic (3-D) tracking system consists of a receiver, hydrophones, and ultrasonic transmitters. The receiver will continuously monitor 16 separate hydrophones distributed throughout the forebay and synchronize the signals as they were received at Lower Granite Dam. Different repetition rates will allow

Figure 2. Tagging station used to implant acoustic tags in juvenile salmon.

the monitoring of multiple transmitters in the array and have the ability to identify individuals. Therefore, the geometry of the array must have sufficient horizontal and vertical separation to allow accurate and precise calculations of the 3-D fish position in the x, y, and z planes. By triangulating the location of the transmitter, the principle used in 3-D fish tracking is the same principle used in Global Positioning Systems (GPS).

Juvenile hatchery and wild steelhead (Oncorhynchus mykiss) and chinook salmon (O. tshawytscha) obtained from the Juvenile Fish Collection Facility at Lower Granite Dam will be used in these studies. Fish will be tagged and released about 12.5 miles upstream of the dam and be held in-river for 24 h prior to being tagged and released. All fish will be greater than 150 mm in fork length and be surgically implanted with ultrasonic transmitters (Figure 2). Transmitters are about 20 mm in length and 6 mm in diameter. Transmitter weight is about 1.5 g and will have a functional life of 10-12 d after activation.

Highlights and Key Findings

The USGS was contracted by the USACE to determine the feasibility of using 3-D telemetry systems to obtain fine-scale fish behavior information in the forebay of Lower Granite Dam. These tests showed that the system was capable of producing 3-D information in the forebay of large hydroelectric projects. Based on the results of the feasibility tests in 1999, a deployment of a 16-hydrophone 3-D telemetry system, used to monitor the movement of juvenile steelhead trout, was implemented in 2000. Out of 225 juvenile hatchery steelhead that were tagged and released as part of the first 3-D acoustic telemetry test, 225 were detected and tracked within the hydrophone array.

The 2000 3-D study showed a behavioral shift in the approach path taken by the migrating juvenile steelhead, which occurred between 100 m and 150 m upstream of the dam. In most cases, fish with short residence times as they passed the dam (i.e., a direct approach with little meandering through the forebay) approached the powerhouse from north to south and followed the flow field toward the BGS and powerhouse at a depth of greater than 4 m. A high proportion of fish with longer residence times (i.e., displaying a milling behavior in the forebay) approached the dam at the gap between the powerhouse and spillbays at a depth of less than 4 m. Many of these shallow, milling fish appeared to be guided by the trash sheer boom, which acted as a surrogate guidance structure similar to the BGS. This behavior may be important in interpreting migration behavior with respect to acceptance or rejection of the RSW surface passage route.

In 2001, an acoustic array was designed with a higher hydrophone density and 1:1:1 spatial separation. As a result, improved precision and accuracy of the 3-D position estimates allowed sub-meter (within 0.3 m) precision within the hydrophone array. The new hydrophone configuration was implemented at Lower Granite Dam for 3-D monitoring in 2002. Results of the 2002 RSW test are currently being analyzed. However, preliminary findings continue to provide evidence that the RSW system is meeting the desired objectives. In summary, a high proportion of fish (from a total sample of 203 chinook salmon, 197 hatchery steelhead and 197 wild steelhead) appeared to enter the RSW. In addition, it appeared that fewer fish meandered in the forebay prior to passing through the RSW. Once the analysis of the 2002 test is complete, the information will be integrated with results from flow modeling to characterize how and why fish behavior is influenced by the RSW structure.

Where Are We Headed In 2003

Three-dimensional fish tracking will be used to examine the movements of acoustically-tagged hatchery steelhead, wild steelhead and chinook salmon as they approach the removable spillway weir (RSW) at Lower Granite Dam. The deployment of the 3-D system in 2003 will be similar to the array design used in 2002. The 3-D system will allow us to gather continuous, fine-scale data on fish as they move close to the RSW and accept or reject the opening. The 3-D information could be combined with near-field water velocity data to provide valuable information on fish behavior caused by changes in water velocities near the RSW.

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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