An acoustic detector of turbot feeding activity

In fish farm conditions, visual observation of fish appetite is often impeded by high fish density and water turbidity. The present study contributes to resolution of this problem by the development of an acoustic method for direct monitoring of turbot feeding activity using sounds emitted by fish during a feeding period. The method uses an acoustic sensor (hydrophone) and a data processing system (acoustic receiver). Feeding sounds were only selected in the 6–8 kHz frequency band to reduce interference from background noise. Variances of these filtered signal amplitudes were then calculated by the processing device and represented as a function of time during a given feeding sequence via a software programme. Calibration tests carried out in a turbot fish farm showed a linear relationship between the acoustic signals produced by feeding fish, measured by the acoustic detector, and their demand for feed pellets (i.e. feeding events) estimated by the hand feeder. The use of this new device, as an objective means for control of food supply by fish farmers to adjust food delivery relative to appetite, is discussed.