Effects of water temperature and dissolved oxygen on daily feed consumption, feed utilization and ž / growth of channel catfish Ictalurus punctatus

Ž . Ž . Ž . Ž . Feed intake FI , feed efficiency FE , protein efficiency ratio PER and weight gain WG of Ž . juvenile channel catfish initially weighing 15.0"0.23 g 10–12 cm initial total length were Ž evaluated under three regimes of time-varying water temperature mean daily water temperature . Ž for Stoneville, MS, USA; mean q3; and, mean y38C and three of dissolved oxygen DO; 100, . 70 and 30% air saturation, at each temperature . Two independent experiments lasting 6 and 8 weeks, respectively, simulated spring and fall temperature and photoperiod patterns. Temperature–oxygen regimes were applied to randomly assigned duplicate 110-l aquaria with individual biofilters. Fish were fed once daily, to slight excess, a commercial catfish floating feed. After 45 min, uneaten feed was collected, dried and weighed; then FI was calculated by difference. Fish in each aquarium were weighed collectively, biweekly. In both experiments higher temperatures and higher DO levels produced increased feed consumption. A multivariate regression model was fitted to the data to describe the combined effects of temperature and DO on FI. There was a progressive reduction in FI as DO declined from 100 to 30% air saturation. In both trials weight gain was higher for fish held 38C above the mean water temperature at 100% air saturation values of DO; whereas, the lowest values of WG were obtained for fish held at 30% air saturation and 38C below the mean water temperature. Weight gain increased with temperature, with maximum rates reached at 27.18C with DO equivalent to 100% air saturation. In contrast, when DO was 30% air saturation, growth rates plateaued as ambient temperature exceeded 22.88C. This model will assist in optimization of feeding practices in channel catfish aquaculture. q 2000 Elsevier Science B.V. All rights reserved.