The influence of temperature and ration on growth, feed conversion, body composition and nutrient retention of juvenile turbot (Scophthalmus maximus)

The influence of two water temperatures (16 and 22 degreesC) on growth, feed conversion, body composition and nutrient retention was investigated in juvenile turbot fed to satiation (0.9% and 1.1% bw day(-1) at 16 and 22 degreesC, respectively) and at restricted rations of 65% and 35% of the satiation level at each temperature. Fish fed the same % rations at 16 and 22 degreesC did not differ in final mean weight or specific growth rate, which decreased at restricted rations. Feed restriction did not result in an increase in size heterogeneity over time at any temperature, as indicated by the stability of the coefficients of variation of weight (DeltaCV(w) = 1.00-1.13%). At both temperatures, the best feed conversion efficiency (FCE) was found at the 65% ration, and the FCE from fish fed the same rations was higher at 16 degreesC (1.30 g g(-1)) than at 22 degreesC (1.17 g g(-1)). A similar trend was found in energy and protein retention levels. At both temperatures, fish fed 35% rations had lower body lipid and higher ash and moisture content compared to fish fed to satiation, with the most pronounced effects on lipid (4.8% vs. 7.8% bw) and ash (4.1% vs. 3.6% bw) at 22 degreesC. Feeding ration proved to be the main differentiating factor in all growth, feed conversion and body composition parameters, whereas additional temperature and/or interaction effects were found in FCE, whole body protein, lipid, moisture and energy contents. Between fish fed 100% and 65% rations, only minor differences were found, but at 35% ration, the rearing temperature of 22 degreesC had a pronounced negative influence, and resulted in a reduction of available anabolic energy for growth and adaptive responses. (C) 2003 Elsevier Science B.V. All rights reserved.