Effect of temperature on growth and energy budget of juvenile cobia (Rachycentron canadum)

Growth and energy budget of juvenile cobia (initial body weight similar to 22 g) at various temperatures (23, 27, 31 and 35 degrees C) were investigated in this study. Maximal ration level (RLmax, %/day) increased as temperature (T, degrees C) increased from 23 degrees C to 31 degrees C but decreased at 35 degrees C, described as a quadratic equation: RLmax=-0.023T(2)+1.495T-17.52. Faecal production (f, mg g(-1) day(-1)) increased with increased temperature (T, degrees C), described as a power function: Inf=0.738lnT-0.806. As temperature increased, feed absorption efficiency in dry weight (FAE(d), %), protein (FAE(p), %) and energy (FAE(e), %) all increased first and then decreased, but the variation of feed absorption efficiency was small, with ranges of 89.59-91.08%, 92.91-94.71%, 93.92-95.32%, respectively. Specific growth rate in wet weight (SGR(w), %/day), dry weight (SGR(d), %/day), protein (SGR(p), %/day) and energy (SGR(e), %/day) showed a domed curve relative to temperature (T, degrees C), described as quadratic equations: SGR(w)=-0.068T(2)+3.878T-50.53, SGR(d)=-0.079T(2)+4.536T-59.64, SGR(p)=-0.084T(2)+4.783T-63.08 and SGR(e)=-0.082T(2)+4.654T-60.99, and SGR(w), SGR(d), SGR(p) and SGR(e) maximized at 28.5 degrees C, 28.6 degrees C, 28.4 degrees C, 28.5 degrees C, respectively, as calculated from the regression equations. The relationships between feed conversion efficiency in wet weight (FCEw, %), dry weight (FCEd, %), protein (FCEp, %), energy (FCEe, %) and temperature (T, degrees C) also took on a domed curve described as quadratic equations: FCEw=-0.726T(2)+39.71T-473.8, FCEd=-0.276T(2)+15.31T-190.6, FCEp=-0.397T(2)+22.05T-277.9 and FCEe=-0.350T(2)+19.39T-239.9, and FCEw, FCEd, FCEp and FCEe maximized at 27.4 degrees C, 27.8 degrees C, 27.7 degrees C and 27.7 degrees C, respectively, as calculated from the regression equations. Energy budget of juvenile cobia fed satiation was 100C=5F+67(U+R)+28G at water temperature 27 degrees C and 100C=5F+70(U+R)+25G at water temperature 31 degrees C, where C is food energy, F is faeces energy, (U+R) is excretion energy and metabolism energy, and G is growth energy. (c) 2006 Elsevier B.V. All rights reserved.