Studies on the development of demand-feeding system in fish aquaculture

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In order to apply demand-feeding system to fish aquaculture, we studied the feeding behavior, growth rate, reward level, diet and feeding device in rainbow trout, red sea bream and yellowtails.1) These fishes learned demand-feeding mostly within several days after subjected to the feeder. The fish showed a good growth performance.2) Rainbow trout displayed daily feeding rhythms with diverse feeding patterns under simulated seasonal conditions. The feeding rhythms were controlled by biological clocks. Trout self-selected macronutrients by means of digestible energies. Time-restricted demand-feeding seemed to be important for the mass aquaculture.3) Demand-feeding of red sea bream reduced the amounts or uneaten foods compared with the automatic feeding. In addition, time-restricted demand-feeding during daytime decreased the uneaten foods, but not the weight gain. Behavioral interaction between the fish, that can or cannot activate the feeding device, was also studied. The daily feeding rhythms were controlled by biological clocks.4) Yellowtails reared in indoor tanks exhibited clear diurnal demand-feeding pattern synchronizing to the given photoperiod, whereas those in outdoor tanks became nocturnal. Moreover, they seemed to maintain routine food intakes by regulating the number of switch-activation when different amounts of food were rewarded. Time-restricted demand feeding effectively decreased the food waste.5) A microcomputer-controlled demand feeding system was designed and developed for outdoor experiments. Importance of switch sensitivity, quick and accurate food deliver was assessed.