An optimum ration was not readily apparent as conversion differed only slightly at high and low rations. Gross (K1) and net (K2) conversion was affected by neither ration size nor temperature, but decreased with increasing fish size. Conversion of the third order (K3) was affected only by temperature, being greater at higher temperatures. Gross and net conversion were consistently lower at cycled temperatures, 16–8 C. Gross and net conversion were similar since the high assimilation efficiency (82.1–97.9%) of walleye (Stizostedion vitreum vitreum) did not greatly alter the latter.Assimilation efficiency was dependent upon diet type, least for invertebrates (82.1% for amphipods and 83.5% for crayfish) and greatest for fish (96.9% for age O perch and 97.9% for emerald shiners). Assimilation efficiency decreased with increasing walleye size (slope of − 0.0045) irrespective of the food organism. Regurgitation of crayfish occurred in two of three trials, and it was not established if this was a natural phenomenon.Maintenance requirement per gram was independent of fish size, but was affected by temperature. Maintenance between temperatures of 4–12 C was similar, 33.3–45.7 cal/g walleye per week, but increased greatly above 12 C. Results from maintenance experiments paralleled Winberg's (1956) approximation of routine metabolism.