2019_programme: DEVELOPMENT OF ACOUSTIC DOPPLER FISH MONITORING FOR APPLICATIONS IN HIGH-ENERGY TIDAL CHANNELS

• Session: 15. Acoustics of marine renewable energy developments
  Organiser(s): Robinson Stephen, Lepper Paul, Blondel Philippe
• Lecture: DEVELOPMENT OF ACOUSTIC DOPPLER FISH MONITORING FOR APPLICATIONS IN HIGH-ENERGY TIDAL CHANNELS
  Paper ID: 821
  Author(s): Dunn Muriel, Zedel Len, Trowse Greg, ,
  Presenter: Dunn Muriel
  Presentation type: oral
  Abstract: Acoustic Doppler profiler systems (ADCPs) are the standard instrument used to monitor ocean currents. These instruments also detect signals scattered by fish, but these signals are normally treated as noise and rejected by ADCP data processing techniques. Those rejected signals do however contain information on fish movement providing an opportunity to extend the application of ADCP technology. The added capability of the ADCP provides a monitoring tool for fish activity and presence in areas that may be impacted by future in-stream hydro energy development projects. We explore this capability through a 37-day deployment of a self-contained bottom-mounted frame equipped with a 600 kHz RD Instruments Workhorse ADCP alongside a 120 kHz BioSonics DTX Submersible Split Beam Echo Sounder system. The deployment took place in Grand Passage, Nova Scotia, at a depth of 25m, where the tidal range is ~5m, and the currents are up to 2.5m/s. We chose this site because it is located in a tidal channel that is identified as having the potential for in-stream tidal generation. Anticipating possible interference, we selected different frequencies and regulated the duty cycles to overlap for half of the total sampling time to assure the collection of uncontaminated data. The split-beam echo sounder shows plumes of scatterers, presumably bubbles, emanating from the surface. Discrete targets are detected throughout the water column within fish schools and as individuals. The corresponding ADCP data detects the same fish schools by using coinciding instances of high intensity and high correlation. The ADCP signal has a lower range resolution but shows less contamination from surface bubbles and weaker scatterers. We present observations for both instruments and contrast their capabilities.
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• Corresponding author: Ms Dunn Muriel
  Affiliation: Memorial University of Newfoundland
  Country: Canada
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