Notes from planning discussions on hydrophone array and marine mammal research.

Discussion Participants

Michel André, William Wilcock, Jim Comeau, Oscar Garcia, Jordi Sorridas

Background

• No/very little information on cetacean migration patterns in the North West Pacific
• Hydrophone arrays could aid in location and tracking of both baleen (gray, fin, blue, humpback, sei, minke, right) and toothed (sperm, orca) whales. System could also be used for vessel ID and tracking.
• Unique opportunity to learn
• Pressure from human activities: necessity of mitigation/conservation actions

Under our current hydrophone configuration...

• Single hydrophones allow the detection of the presence/absence of cetaceans
• No information on distribution/migration patterns
• Limited to a certain area around the hydrophone

Perspectives

• Arrays of hydrophones allow the location/tracking of acoustic sources
• Cetaceans produce a wide variety of acoustic signals, from very low frequency sounds to ultrasonic clicks
• Odontocetes (toothed whales) produce mid- (a few kHz) to high frequency sounds (up to 110kHz) (communication and echolocation)
• Mysticetes (baleen whales) produce mid- (up to a few kHz) low frequency sounds (down to 20 Hz) (mainly for communication)
• This implies that the aperture of the array of hydrophones must be adapted to the sound characteristics to be able to track a majority of species present in the area of NEPTUNE. The aperture of the array being dependent on the wave length of the signal.
• Toothed whales: small aperture array in the order of a few meters
• Baleen whales: large aperture array in the order of a few kilometers
• Building small aperture arrays at different locations would allow to combine both above requirements
• Ideally: three (3) arrays around the continental edge, plus another one in deep waters

Instrumentation Requirements, power & communications, platform requirements

• Arrays of four (4) digital hydrophones in a tetrahedral configuration (stainless steel platform)
• One (1) array at each of the following locations, three (3) in total:
  • Folger Passage
  • Barkley Canyon
  • ODP 889
• One (1) at any of the following locations, one (1) in total:
  • Middle Valley
  • Endeavour
  • ODP 1027
• Sixteen (16) hydrophones in total if not using existing hydrophones

Manufacturer/budget

• Two companies build digital hydrophones: NAXYS and SMID
• Quotes to be asked and confirmed but a rough budget of around 100.000 euros is anticipated

What kinds of requirements and research expertise are required? Who should be involved?

• Synchronization between the different arrays to track individuals (done with seismometers)
• Research expertise: bioacoustics, signal processing, beamforming (spectral and spatial analysis), real-time processing, development of tracking modules for each acoustic source, including artificial (shipping) for long-term noise interactions
• The development of the hydrophone array architecture should be part of a particular proposal
• Duration: once the arrays are deployed and the software written and implemented: long-term use and study with no additional costs (except regular maintenance)
• Dedicated workshop with parties to identify existing solutions and write proposal.

Possible Collaborators

John Ford, Harald Yurk, Michel André, other (at the moment) not identified parties.