Effects of feeding frequency on metabolism of juvenile walleye

Abstract

The effects of feeding frequency (1, 2, 3, or 15 times daily) on oxygen consumption (OC, mg O 2 kg −1 h −1) and ammonia excretion, (AE, mg TAN kg −1 h −1) of walleye ( Stizostedion vitreum) are described. Walleye were reared at a practical culture density of 35·4 kg m −3 in a single-pass system at 23·2°C. Diurnal variation in metabolic rates were related to feeding, not to photoperiod. Minimum OC rates occurred 30 min before the first feeding of the day, which was the longest average time since the last feeding. Metabolic rates increased immediately after feeding. The maximum rates for OC were 36–49% higher than the minimum rates, and 14–22% higher than the 24-h mean rate. Maximum rates for AE were 137–409% higher than the minimum rates, and 39–87% higher than the mean rates. There was a highly significant difference in the mean metabolic rates related to feeding frequency. The mean OC rate for 1 feeding day −1 (222·0 mg O 2 kg −1 h −1) was greater than the mean rates for 2, 3 and 15 feedings day −1. The OC rate for 1 feeding day −1 was 50·6% greater than the rate for 15 feedings day −1 (147·4 mg O 2 kg −1 h −1), the lowest mean rate. Mean and maximum oxygen/feed ratio (OFR, kg O 2 kg −1 feed fed day −1), varied inversely with feeding frequency. The mean ammonia/feed ratio (AFR) was similar for all but the 3 feedings day −1 treatment, but the maximum AFRs for 2 and 15 feedings day −1 were lower than the AFRs for 1 and 3 feedings day −1. AE was directly proportional to OC; the regression equations were highly significant, but specific for feeding frequency.