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

Abstract

Growth and energy budget of juvenile cobia (initial body weight ∼ 22 g) at various temperatures (23, 27, 31 and 35 °C) were investigated in this study. Maximal ration level (RL max, %/day) increased as temperature ( T, °C) increased from 23 °C to 31 °C but decreased at 35 °C, described as a quadratic equation: RL max = −0.023 T 2 + 1.495 T − 17.52. Faecal production ( f, mg g − 1 day − 1 ) increased with increased temperature ( T, °C), described as a power function: ln f = 0.738ln T − 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, °C), described as quadratic equations: SGR w = − 0.068 T 2 + 3.878 T − 50.53, SGR d = − 0.079 T 2 + 4.536 T −59.64, SGR p = − 0.084 T 2 + 4.783 T − 63.08 and SGR e = − 0.082 T 2 + 4.654 T − 60.99, and SGR w, SGR d, SGR p and SGR e maximized at 28.5 °C, 28.6 °C, 28.4 °C, 28.5 °C, respectively, as calculated from the regression equations. The relationships between feed conversion efficiency in wet weight (FCE w, %), dry weight (FCE d, %), protein (FCE p, %), energy (FCE e, %) and temperature ( T, °C) also took on a domed curve described as quadratic equations: FCE w = − 0.726 T 2 + 39.71 T − 473.8, FCE d = − 0.276 T 2 + 15.31 T − 190.6, FCE p = − 0.397 T 2 + 22.05 T − 277.9 and FCE e = − 0.350 T 2 + 19.39 T − 239.9, and FCE w, FCE d, FCE p and FCE e maximized at 27.4 °C, 27.8 °C, 27.7 °C and 27.7 °C, respectively, as calculated from the regression equations. Energy budget of juvenile cobia fed satiation was 100 C = 5 F + 67( U + R) + 28 G at water temperature 27 °C and 100 C = 5 F + 70( U + R) + 25 G at water temperature 31 °C, where C is food energy, F is faeces energy, ( U + R) is excretion energy and metabolism energy, and G is growth energy.