Abstract
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.
Highlights
In terrestrial animal farming, there are numerous examples of farmers observing the individual behaviours of animals either directly or with remote monitoring techniques and adjusting farm practices with this information (e.g. Tebot et al, 2009; Darr and Epperson, 2009; Terrasson et al, 2016)
Our experiments were conducted in cages of 30 m depth and the transmitters were set up with a depth range of 0–50 m, leading to a depth resolution of approximately 0.2 m. All tags transmitted their data at an acoustic carrier frequency of 69 kHz, with each transmission encoding a unique tag identification number (ID) and the present depth value registered by the sensor
Two individuals originally equipped with both Data Storage Tags (DSTs) and acoustic tags were found to only contain one tag when slaughtered
Summary
There are numerous examples of farmers observing the individual behaviours of animals either directly or with remote monitoring techniques and adjusting farm practices with this information (e.g. Tebot et al, 2009; Darr and Epperson, 2009; Terrasson et al, 2016). There are numerous examples of farmers observing the individual behaviours of animals either directly or with remote monitoring techniques and adjusting farm practices with this information Tebot et al, 2009; Darr and Epperson, 2009; Terrasson et al, 2016) In aquaculture settings, both the large number of small animals under production and the underwater environment make this approach more difficult. The sheer number of fish at each farm makes it difficult for farmers to maintain an overview of production and integrate information from individuals into their farming strategies. This represents a challenge, as ethical considerations require farm operations to secure the welfare of the fish.
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