Optimization of feeding schedules in salmon hatcheries

Abstract

A methodology is developed that determines feeding schedules which will reduce total food consumption for coho salmon in a hatchery during the rearing period. The method presented assumes that the feeding level has a parabolic mathematical form with respect to time. Coefficients of this parabola are converged upon in such a way that the fish achieve a particular size on a chosen release date and simultaneously total food consump tion for the rearing period is minimized. The indicator of feeding level chosen is a nondimensional parameter that equals one at the minimum feeding rate resulting in maximum growth rate and equals zero at a feeding rate that results in a zero growth rate. Results show that for long rearing periods corresponding to rearing in unheated water, the feeding level should be low initially and gradually increase towards the end of the rearing period. Conversely, for rearing periods simulating the accelerated growth periods that occur in heated hatcheries, feeding levels should in general be high at the beginning and gradually decrease throughout the rearing period though sometimes in creasing towards the end. In general, it has been shown that optimum feeding schedules sacrifice efficiency at the beginning of the rearing period when little weight is being gained and max imize efficiency at the end of the rearing period when the greatest amount of weight is being gained. This is in contrast to schedules often devised by hatchery managers to achieve a specified size at a particular date. These schedules may sacrifice efficiency at the end of the rearing period to achieve the goal.