Rate of Food Digestion by Yellow Perch (Perca flavescens) in Relation to Size of Perch, Size and Type of Food, and Temperature
James C. Schneider
Abstract.-Laboratory experiments were performed on the rate of food digestion by yellow perch. Perch were fed single food items of known size, and then sacrificed periodically to determine the amount of food remaining in their stomachs. In an initial experiment, the digestion rate of food which had been inserted forcibly into the esophagus was compared to the digestion rate of food which had been eaten voluntarily. In other experiments, I varied the temperature (7. 8, 14. 4, 22. 2, and 27. 2 C), size of perch (9.. 7, 28. 2, 49.1, and 105. 8 g),), size of food item (0. 09 and 1. 9% of the weight of the perch), and type of food (fathead minnows and crayfish). I found that: (l) digestion rate of force-fed food was similar, on the average, to that of food eaten voluntarily; (2) time required for complete evacuation of the stomach was linearily related to temperature on a log-log scale; (3) large perch digested more grams of food per hour than did small perch. However, the amount of time required for evacuation of a meal of the same relative size-2. 1% of the weight of the perch-was independent of perch size; (4) a small food item was digested at a slower rate, but in less time, than a large food item; and (5) crayfish were evacuated more slowly than were fish. The yellow perch digested food more rapidly than did the European perch or other species of fish as reported in the literature.