Download PDF - COINAtlantic

11 th International Symposium for GIS and Computer Cartography for Coastal Zones ManagementAcoustic backscatter at 200 kHz (dB)Figure 1. Data cube showing a 14-month segment of a 6-year time-series of 200 kHz backscatter for the VENUS site inSaanich Inlet, British Columbia, Canada.Single-frequency acoustic time series in the Strait of GeorgiaAnother single-frequency AWCP (200 kHz) was installed on the Delta Dynamic Laboratory (DDL) at the base ofthe Fraser River Slope in May 2011, along with other instruments. The objective was to collect various oceanographicdatasets to understand the marine habitat and monitor the presence of marine organisms (Xie and Dewey,2011). The acoustic backscatter data collected after dusk and at rising tide on September 4 and 5, 2011 clearlyshowed dense schools of fish at depths between 10 and 20 m, as well as occasional individuals between 20 and 80m. It was inferred from data collected by the Pacific Salmon Commission (PSC) that those fish were likely sockeye(Oncorhynchus nerka) and pink (Oncorhynchus gorbuscha) salmon. The coupling of swimming behaviour and calibratedtarget strengths helped determine that pink salmon were primarily at surface, whereas sockeye were found atlower depths. Between 600,000 and 800,000 salmon were detected migrating up the Fraser River at that time.Multiple-frequency acoustic time series in Saanich Inlet, BC, CanadaRecent improvements to the single-frequency AWCP have added multiple calibrated frequencies that allow informationabout species composition and abundance to be deduced from acoustic backscatter data. The new AZFP isa SONAR that supports up to four frequencies in a single housing. It can be configured as part of an underwaterobservatory, or as a low power, battery-operated device capable of autonomously collecting data at high temporaland spatial resolutions for periods of up to a year. The available operating frequencies are 38, 125, 200, 455, and 770kHz. The transducers are co-located, with the same nominal beam widths of 7° or 8°, except at 38 kHz, where thebeam width is 12°. The standard AZFP can be moored at depths up to 300 m, and with modified transducers as deepas 600 m.207