1. O CEAN A COUSTIC W AVEGUIDE R EMOTE S ENSING (OAWRS) Helen Dickson

2. R EVIEW : A CTIVE A COUSTIC S ENSING An acoustic signal is generated Sound waves travel through the water and scatter off objects Backscattered sound is recorded

3. R EVIEW : C ONVENTIONAL F ISH F INDING S ONAR (CFFS) Uses active acoustic sensing Sends sound waves straight down through the water column

4. P ROBLEMS OF C ONVENTIONAL F ISH F INDING S ONAR Attenuation Frequency Image size Sampling frequency

5. O CEAN A COUSTIC W AVEGUIDE R EMOTE S ENSING Method of active acoustic sensing Developed by MIT Sends sound waves horizontally through the water column

6. A COUSTIC W AVEGUIDES Physical structures for guiding waves Allow acoustic waves to travel long distances with little attenuation The continental shelf as a waveguide

7. O CEAN A COUSTIC W AVEGUIDE R EMOTE S ENSING Little attenuation Lower frequency Much larger image (1,000s of square km’s) Images created every minute (or less)

8. I MAGE GENERATED BY OAWRS

9. M OVIE GENERATED BY OAWRS

10. A PPLICATIONS Shoal Characteristics: Formation (critical density) Migration Leaders Monitor and conserve fish populations Identify fish species based on return signal

11. A PPLICATIONS Acoustic clutter Acoustic returns from objects in the water other than the intended target Is it a submarine or is it a school of fish? Important in Navy operations OAWRS allows more detailed information to be gathered

12. R EFERENCES Holden, Constance. Sound Sightings. 2006. Science. 313(5788):777 Makris, Nicholas C., et al. Fish Population and Behavior Revealed by Instantaneous Continental Shelf-Scale Imaging. 2006. Science. 311(5761):660-663. Makris, Nicholas C. et al. Critical Population Density Triggers Rapid Formation of Vast Oceanic Fish Shoals. 2009. Science. 323(5922):1734-1737. Makris, Nicholas C. Acoustic Clutter and Ocean Acoustic Waveguide Remote Sensing (OAWRS) in Continental Shelf Environments. http://www.onr.navy.mil/sci_tech/32/reports/docs/08/oamakris.pdf Makris, Nicholas C. Continuous Monitoring of Fish Population and Behavior by Instantaneous Continental-Shelf-Scale Imaging with Ocean Waveguide Acoustics. http://www.onr.navy.mil/sci_tech/32/reports/docs/08/npmakris.pdf Ratilal, Purnima et al. Long range acoustic imaging of the continental shelf environment: The Acoustic Clutter Reconnaissance Experiment 2001. 2005. Journal of The Acoustic Society of America. 117(4):1977-1998. Woods Hole Oceanographic Institution. 2007. http://www.whoi.edu/page.do?pid=10897&i=2041&x=131