A HYDROACOUSTIC WASTE FEED CONTROLLER FOR TANK SYSTEMS

The objective of this work was to develop a commercially viable method to reduce waste feed and thus improve production efficiency and reduce discharge of solids and nutrients within tank based aquaculture systems. We developed and custom fabricated a feeding controller which uses ultrasound to detect uneaten feed and controls feeding events based upon appetite satiation as measured by the quantity of waste feed detected. During feeding, the developed device functions as a combination ultrasonic detector, feedback controller, and interval timer. The device functions as a feedback controller by ultrasonically sampling the stock tank effluent and turning off the feeder when an excessive amount of feed enters the effluent flow. After feeding has been inactivated, the ultrasonic waste feed controller operates as an interval timer and provides a user selected delay between feedings. A custom hydroacoustic probe assembly was developed to detect uneaten feed. The controller can be calibrated by adjusting the transducer signal gain to detect signals resulting from feed pellets, while reducing signals resulting from faeces. The controller has an adjustable set-point for deactivating the feeder circuit based upon the number of feed pellets detected by the transducer and a programmable delay time interval (from 5 to 160 min) to set the time between feedings. The controller also has an adjustable sampling rate for detection at different pipe velocities and an adjustable observation volume for use in standard 2, 3, 4 and 6 inch diameter effluent pipes. The cost in materials and labour to produce this waste feed controller was estimated at around $100 (U.S.).