Figure 6. Testing tag detection. After hydrophones were deployed, a Ping-Around™ wasperformed to verify hydrophone positio...
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Evaluating Fish Passage in Noisy Environments Using Acoustic Telemetry


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Poster presented by Tracey Steig at the Fish Passage 2013 Conference in Corvallis, OR.

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Evaluating Fish Passage in Noisy Environments Using Acoustic Telemetry

  1. 1. Figure 6. Testing tag detection. After hydrophones were deployed, a Ping-Around™ wasperformed to verify hydrophone positions and hydrophone detectability. During this test, thehydrophones are changed from a receiving only state to an active “pinging” state whereby theytransmit the same codes as fish tags. Next, an active acoustic tag (the same size and outputthat were subsequently implanted in fish) was towed behind a boat throughout the tailrace totest array coverage and tracking performance.Tags were programmed to transmit two separate “coded” signals (3 ms, and 5 ms) and threeseparate non-coded signals (1 ms, 3 ms, 5 ms). Through preliminary test, we determined thatthe 5 ms coded pulse had the greatest range and detectability, which was then selected for thefish. The initial test also showed that all hydrophones were functional at setup and thathydrophones had sufficient detection range to locate tagged fish present in the high noiseconditions in the tailrace.1Tag Tracking Results in the TailraceAcoustic tagging studies routinely provide information about fish presence and absence. Thisdetection information is combined into a chronology of time-stamped tag detections to measurefish survival and fish passage estimates, among others. Beyond this simple tag detection data, iftag detections are uniformly spaced to a high level of precision then the detection time series canbe used to assess fish behavior even in acoustically noisy environments, such as the tailrace of ahydroelectric dam.In Brazil’s São Francisco River, the Federal University of Lavras Department of Biology (UFLA),and one of Brazil’s largest electrical power producers and distributors, the Companhia Energéticade Minas Gerais (Cemig) began an unprecedented study. In order to improve fisheriesmanagement downstream of the Três Marias Dam, they set out to monitor fine-scale fish behavior.Acoustically tagged fish were simultaneously detected and identified in real-time at a distance up to100 m (328 ft) in the turbulent water of the dam’s tailrace. An active part of Cemig’s conservationinitiative, Peixe Vivo Program, the results will be used to increase the understanding of how fishmove and behave near power generating units during various stages of operation.In this poster, we document equipment (Figure 1), implementation, methodology and additionalconsiderations (Figures 3-4) for acoustic tag tracking in acoustically loud environments.Additionally, we will discuss the procedures for testing tag tracking results in the tailrace (Figure 6).This work was also documented for a PhD thesis for UFLA researcher and Oregon State Universityexchange-student, Fabio Suzuki.AbstractSolutionsWe determined that detecting and tracking the behavior of acoustically tagged fish in noisytailrace environments is feasible. The methods that we used for our feasibility study weresufficient to address research objectives and provided two-dimensional tracking information fromtagged fish. Spatial resolution of fish position was significantly improved by using encodedpulses and appropriately spaced hydrophones within the study area.When multiple hydrophones are deployed to provide fine-scale 2D or 3D fish track data, thensudden behavioral changes and quantifiable patterns of swimming behavior can be measured.High-resolution fish track data provides valuable information that can aid in characterizingtailrace swimming behavior under different plant operational regimes.The conclusion of this project will provide the group with vital fisheries data and correlated tagvisualizations (via HTI’s AcousticTag Software) to accurately illustrate how fish approach one ofthe plant’s noisiest and most turbulent areas, the powerhouse tailrace.ConclusionTracey Steig, Colleen Sullivan & Sam JohnstonHTI Hydroacoustic Technology, Inc. (206) 633-3383 tsteig@HTIsonar.comEvaluating Fish Passage in Noisy Environments Using Acoustic TelemetryFish Passage 2013June 25-27 2013Figure 4. Proper hydrophone deployment. With an adequately spaced hydrophone array, taggedfish can still be detected and tracked in hydropower dam tailraces. Adequate spacing may accountfor the reduction in tag ranges due to higher levels of noise and air entrainment in the tailraceenvironment. Detection ranges among HTI’s acoustic tags and hydrophones average up to 1 kilo-meter (33,280 ft), however, to compensate for the amount of noise and entrained air present, theywere placed and tested in closer proximity (50 m / 164 ft). The geo-referenced image aboveillustrates shallow and deep hydrophone placement.Figure 2. Feasibility testing in-situ. Detection feasibility tests were conducted near Brazil’sTrês Marias Dam located on the São Francisco River. The image above left and top right wastaken when the dam was non-operational (no high noise conditions) so that the hydrophonescould be deployed and tested. The lower right image illustrates a hydropower dam turbine thatcan create highly turbulent waters in the dam’s tailrace.Downstream at Hydropower DamsData courtesy of the Federal University of LavrasDept. of Biology (UFLA), the Companhia Energéticade Minas Gerais (Cemig), one of Brazils largestpower generators & distributors, & Peixe VivoProgram, a Cemig conservation initiative.AcknowledgmentsDouble pulse tag in noisyenvironment without subcode filter.Tag TagDouble pulse tag in noisyenvironment with subcode filter.Figure 5. Tag parameters and filters for overcoming noise. To overcome noise challenges,combined filters can be used (e.g., filters for subcodes, period, threshold, noise band). Theexample above shows a double pulse tag with and without a subcode filter in a noisy environment.Also vital to effectively tracking in noisy environments is the ability to control (increase) the energyof the tag’s pulse. Increasing the width of the pulse (or burst), increases the energy in the pulse,allowing it to travel farther through entrained air and noisy environments. Pulse encoding and digitalsignal processing techniques compress the output pulse, allowing increasing resolution andmaximum detection range (Ehrenberg and Steig 2003).Figure 3. Sources of Noise. Challenges often found in hydropower dam tailraces include theenvironmental factors noted above. Alone or together, they can significantly reduce the range ofsignal detection for acoustic tags, making it difficult to detect and acquire fine-scale behavioral data.Challenges, Methodology & ConsiderationsEntrained Air(Scattering)Density Differences(Turbulence, SoundSpeed Changes)Debris(Scattering, Blocking)Acoustic Noise(Constructive & DestructivePhase Interference)Figure 1. Acoustic Telemetry System. The acoustic telemetry system includes HTI’s Model 290Acoustic Tag Receiver, hydrophones, Model 795 Acoustic Tags, and a computer with AcousticTagSoftware to receive and process tagged fish positioning data.Equipment for Detecting Fish PassageAcoustic Tags