Effects of fish size and feeding frequency on metabolism of juvenile walleye

Abstract

The effects of fish weight and feeding frequency on metabolism of juvenile (204 to 425 g) walleye ( Stizostedion vitreum) reared under intensive culture conditions are described. The metabolic rates (mg kg − h −1) for oxygen consumption (OC) varied inversely with fish weight (BW). In the rectilinear arithmetic regression, BW accounted 86% of the variability in the metabolic rate measured by OC. The ammonia excretion (AE)-BW relationship was more variable, regressions for fish given 15 feedings per day were significant but not for fish given 2 and 3 feedings per day. For a data set of 82 measures of average daily AE mg kg −1 h −1 rates, the slope of the log 10−log 10 AE to BW regression was significant (P>0·01) but BW accounted for only 30% of the variability in AE. The exponent ( b) for the general equation M BW = aBW b relationship, derived from the log 10−log 10 regression, was −0·465 for OC-BW and −0·460 for AE-BW. The average daily rates of OC and AE were not significantly affected by feeding frequencies of 2, 3, and 15 times daily. However, the variance in OC, but not AE, was significantly affected by feeding frequency after the effects of fish weight were removed by analysis of covariance. The variance in OC declined with increasing number of feedings per day for 2 to 15 feedings per day. The implications to fish culture are discussed.