Coherent high-speed acoustic communication inside a commercial atlantic salmon pen

Fish telemetry is a potential method to monitor the well-being of farmed fish, where a reference group of fish are equipped with sensors tags that oversee their health and wirelessly transmit the data. Many fish must be tagged to get statistically reliable information. In this paper, very-high-frequency (250 kHz) acoustic channels are characterized using data recorded in an Atlantic salmon pen containing 180 000 fish. The results reveal vertical pen channels characterized by a direct path and a delayed tail of fluctuating multipath arrivals with an angular spread and a coherence time of order 14 ms. It is demonstrated that multichannel equalization applied to a 64-element hydrophone array enables high-speed (78 kbps) coherent communication in short bursts. We discuss the possibilities of using high-speed acoustic communication for fish telemetry and show that it has the potential of serving hundreds of distributed unsynchronized fish tags.