| 摘要 |
A method and system are provided for obtaining acoustic data for use in determining fish populations in shallow waters. The system includes an acoustic source comprising a buoyancy unit, anchor, and a broadband acoustic transmitter, and a cable which connects the buoyancy unit to the anchor and supports the transmitter. The system also includes one or more acoustic receivers employing hydrophones and including a similar buoyancy unit, anchor, and cable. When the source and receiver are (separately) deployed, the respective cables are released so that the buoyancy units rise in the water. Thus, with the source and receiver anchored to the bottom the transmitter and hydrophones are suspended at a depth near the bottom (below the thermocline if there is a thermocline) determined by the cable length released. At this time, acoustic signals are transmitted from the acoustic transmitter to the hydrophones for recording. Next, the cables are again released so that the buoyancy units rise higher in the water and thus the transmitter and hydrophones are suspended at greater heights from the bottom, i.e., near the surface (above the thermocline if there is a thermocline). When this is done, acoustic signals are again transmitted from the acoustic transmitter to the hydrophones for recording. The source and receivers are ultimately released from the respective anchors for recovery.
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