Maximum Feeding Rations and Maximum Growth Rates as a Function of Temperature - Derived by Using a Traditional Feeding Chart for Rainbow Trout (Oncorhynchus mykiss)

For profitable operation of aquaculture facilities, it is necessary to feed fish preferably with the optimum feeding rate. The appetite and thus the optimum feeding rate depend on the instantaneous body mass and increase with temperature up to a certain limit. However, the food consumption continues to rise even if the temperature exceeds this limit, but the food is no longer completely digested. Fish need to be fed less than they will eat. Overfeeding and excessive temperatures generate unnecessary costs; also decreasing the water quality and finally the profit. An optimization of those relationships regarding profits and value chain is complicated because a precise functional relationship between feeding and growth does not exist yet. Feeding data are provided usually in tabular form and the relationship between food intake and growth is modeled by the feed conversion ratio. However, the feed conversion ratio is a function of body mass and temperature, thus calculations based on those relationships are inaccurate. To gain precise estimates of feeding data a feeding function was developed based on the approach of Pütter (1920) and the approach of Ivlev (1939). Key parameters of this model are the reference assimilation rate, its temperature constant, the limit temperature and the food efficiency. The first three parameters were determined applying the least squares method on data of feeding experiments of Hinshaw (1999) with rainbow trout (Oncorhynchus mykiss). Further experiments are necessary (Bethke et al. 2013) for the estimation of the food efficiency and maintenance rate. In addition to the precise control of food intake, the new model should also allow the calculation of the percentage of food which is not utilized. A more complete picture of the value chain is available