Passive and active acoustic monitoring of mulloway in the Swan River
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Date
2017Author
Parsons, Miles, J G
Anning, Justin
Parnum, Iain M.
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Passive acoustic monitoring is a standard tool to monitor vocal marine fauna. High-frequency multibeam echosounders
have developed rapidly in recent years, with the number of applications for detecting and tracking biological
targets expanding significantly. In the Swan River, Perth, mulloway (Argyrosomus japonicus) form aggregations
each austral summer. Here, a Kongsberg MS1000 scanning sonar and a CMST Underwater Sound
Recorder (USR) were deployed onto the riverbed in 12 m of water. The sonar scanned to ranges of 50 and 75
m (angular resolution, 0.45°), taking approximately 120 s for one full 360° scan. The USR sampled at 6 ksps for
five of every fifteen minutes. The sonar detected fish travelling slowly (typically <0.5 ms-1) within its range, while
the passive recorder detected the development of an evening chorus, starting with individual calling fish. One
example target remained within the field of view of the sonar for over an hour, detected 55 times as it moved
≈100 m. Simultaneously, the USR recorded mulloway vocalisations, with received levels approximating those
predicted for a mulloway at the range detected by the sonar. This study outlines one of the first successes of
matching passive and active acoustic tracking of vocal fish, as a precursor to using sonar techniques to verify
estimates of calling numbers of fish from passive acoustic monitoring.