Apparent heat increment and feeding strategy in walleye, Stizostedion vitreum vitreum

Abstract

Apparent heat increment (AHI), the expenditure of energy associated with the ingestion and conversion of foodstuffs to metabolically useful substances, was measured for juvenile walleye fed a nutritionally balanced formulated diet (20°C). Number of walleye, of similar individual weight, maintained in identical metabolic chambers (10, 20 and 30 fish/chamber) did not significantly influence AHI when expressed on the basis of an individual of 35 g. AHI relative to digested energy (DE) for groups of 10 walleye varied inversely with the daily ration of food which ranged between 0.4 and 1.6% live body weight of the group. The reduction in AHI relative to DE with increases in meal size is attributed to a decrease in the energy requirements to mechanically process food-stuffs. AHI relative to DE was not demonstrably affected when the daily allocation of food was divided equally into one, two or three feedings. Applications to walleye culture are discussed.