Biomonitoring using tagged sentinel fish and acoustic telemetry in commercial salmon aquaculture: A feasibility study

- Prototype acoustic telemetry system for real time monitoring of fish in fish farms.
- System performance verified through field experiment at commercial scale fish cages.
- System successfully collected the majority of the data acoustically communicated in the cage.
- Acoustic telemetry is a viable tool for real time monitoring of individual fish in industrial fish farming.

We tested if it is technically feasible to monitor fish in real-time in full-scale commercial fish farms using acoustic telemetry. 31 Atlantic salmon were equipped with acoustic transmitter tags containing depth sensors. Tagged fish were monitored for three months in two industrial scale sea-cages containing 180000 and 150000 fish, respectively. Each cage was fitted with two prototype acoustic receiver units designed to collect, interpret and store the information transmitted by the acoustic transmitter tags. Ten in each cage were also equipped with Data Storage Tags (DSTs) containing depth sensors to record individual-based datasets for comparison with the acoustically transmitted datasets. After compensation for sample loss caused by expected acoustic interference between the transmitter tags, the resulting dataset revealed that the receiver units collected 90-95% of the signals in both cages. Acoustic communication conditions in the sea-cages were not strongly impaired by factors such as fish density and local noise. Further, the dataset from the acoustic transmitters had comparable resolution and quality to that produced by the DSTs. However, acoustic tags provide data in real time and enable farmers to respond to the received information with farm management measures, whereas archival tags such as DSTs need to be retrieved and downloaded and hence have no real-time applications. We conclude that acoustic telemetry is feasible as a method to monitor the depth of fish in real-time commercial aquaculture.