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

1. Figure 6. Testing tag detection. After hydrophones were deployed, a Ping-Around™ was
performed to verify hydrophone positions and hydrophone detectability. During this test, the
hydrophones are changed from a receiving only state to an active “pinging” state whereby they
transmit the same codes as fish tags. Next, an active acoustic tag (the same size and output
that were subsequently implanted in fish) was towed behind a boat throughout the tailrace to
test array coverage and tracking performance.
Tags were programmed to transmit two separate “coded” signals (3 ms, and 5 ms) and three
separate non-coded signals (1 ms, 3 ms, 5 ms). Through preliminary test, we determined that
the 5 ms coded pulse had the greatest range and detectability, which was then selected for the
fish. The initial test also showed that all hydrophones were functional at setup and that
hydrophones had sufficient detection range to locate tagged fish present in the high noise
conditions in the tailrace.
1
Tag Tracking Results in the Tailrace
Acoustic tagging studies routinely provide information about fish presence and absence. This
detection information is combined into a chronology of time-stamped tag detections to measure
fish survival and fish passage estimates, among others. Beyond this simple tag detection data, if
tag detections are uniformly spaced to a high level of precision then the detection time series can
be used to assess fish behavior even in acoustically noisy environments, such as the tailrace of a
hydroelectric 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 Energética
de Minas Gerais (Cemig) began an unprecedented study. In order to improve fisheries
management 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 to
100 m (328 ft) in the turbulent water of the dam’s tailrace. An active part of Cemig’s conservation
initiative, Peixe Vivo Program, the results will be used to increase the understanding of how fish
move and behave near power generating units during various stages of operation.
In this poster, we document equipment (Figure 1), implementation, methodology and additional
considerations (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 University
exchange-student, Fabio Suzuki.
Abstract
Solutions
We determined that detecting and tracking the behavior of acoustically tagged fish in noisy
tailrace environments is feasible. The methods that we used for our feasibility study were
sufficient to address research objectives and provided two-dimensional tracking information from
tagged fish. Spatial resolution of fish position was significantly improved by using encoded
pulses and appropriately spaced hydrophones within the study area.
When multiple hydrophones are deployed to provide fine-scale 2D or 3D fish track data, then
sudden behavioral changes and quantifiable patterns of swimming behavior can be measured.
High-resolution fish track data provides valuable information that can aid in characterizing
tailrace swimming behavior under different plant operational regimes.
The conclusion of this project will provide the group with vital fisheries data and correlated tag
visualizations (via HTI’s AcousticTag Software) to accurately illustrate how fish approach one of
the plant’s noisiest and most turbulent areas, the powerhouse tailrace.
Conclusion
Tracey Steig, Colleen Sullivan & Sam Johnston
HTI Hydroacoustic Technology, Inc. (206) 633-3383 tsteig@HTIsonar.com
Evaluating Fish Passage in Noisy Environments Using Acoustic Telemetry
Fish Passage 2013
June 25-27 2013
Figure 4. Proper hydrophone deployment. With an adequately spaced hydrophone array, tagged
fish can still be detected and tracked in hydropower dam tailraces. Adequate spacing may account
for the reduction in tag ranges due to higher levels of noise and air entrainment in the tailrace
environment. 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, they
were placed and tested in closer proximity (50 m / 164 ft). The geo-referenced image above
illustrates shallow and deep hydrophone placement.
Figure 2. Feasibility testing in-situ. Detection feasibility tests were conducted near Brazil’s
Três Marias Dam located on the São Francisco River. The image above left and top right was
taken when the dam was non-operational (no high noise conditions) so that the hydrophones
could be deployed and tested. The lower right image illustrates a hydropower dam turbine that
can create highly turbulent waters in the dam’s tailrace.
Downstream at Hydropower Dams
Data courtesy of the Federal University of Lavras'
Dept. of Biology (UFLA), the Companhia Energética
de Minas Gerais (Cemig), one of Brazil's largest
power generators & distributors, & Peixe Vivo
Program, a Cemig conservation initiative.
Acknowledgments
Double pulse tag in noisy
environment without subcode filter.
Tag Tag
Double pulse tag in noisy
environment 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). The
example 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 energy
of 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 digital
signal processing techniques compress the output pulse, allowing increasing resolution and
maximum detection range (Ehrenberg and Steig 2003).
Figure 3. Sources of Noise. Challenges often found in hydropower dam tailraces include the
environmental factors noted above. Alone or together, they can significantly reduce the range of
signal detection for acoustic tags, making it difficult to detect and acquire fine-scale behavioral data.
Challenges, Methodology & Considerations
Entrained Air
(Scattering)
Density Differences
(Turbulence, Sound
Speed Changes)
Debris
(Scattering, Blocking)
Acoustic Noise
(Constructive & Destructive
Phase Interference)
Figure 1. Acoustic Telemetry System. The acoustic telemetry system includes HTI’s Model 290
Acoustic Tag Receiver, hydrophones, Model 795 Acoustic Tags, and a computer with AcousticTag
Software to receive and process tagged fish positioning data.
Equipment for Detecting Fish Passage
Acoustic Tags