Effects of rhythmic temperature change on the growth, body composition and energy budget of hybrid grouper (Epinephelus lanceolatus male x Epinephelus fuscoguttatus female)

摘要

Effects of rhythmic temperature change on the growth, body composition and energy budget of hybrid grouper (Epinephelus lanceolatus male x E. fuscoguttatus female) were investigated. Nine groups of fish received repeating cycles of low-temperature manipulation (22 degrees C) for 1, 2 and 4 days followed by recovery temperature (28 degrees C) for (3, 7 and 11 days), (6, 14 and 22 days) and (12, 28 and 44 days) respectively, designated as L1R3, L1R7, L1R11, L2R6, L2R14, L2R22, L4R12, L4R28 and L4R44 respectively. In the control group (C), fish were reared at 28 degrees C throughout the whole experiment. After 96-day feeding trail, the final weight, relative weight gain rate, specific growth rate, food conversion efficiency and apparent digestibility coefficient of fish in L4R28 were significantly higher than those of control (p &.05). The crude protein contents of fish in L2R14, L2R22, L4R12, L4R28 and L4R44 were significantly higher compared to the control (p &.05). According to energy budget, fish in L4R28 exhibited significantly higher proportion of food energy assimilated into growth and lower proportion consumed for excretion than the control fish (p &.05). These results indicated the occurrence of complete or over growth compensation in hybrid grouper, and the use of repeated cycles of low temperature (22 degrees C) for 4 days followed by recovery temperature (28 degrees C) for 28 days could obtain enhanced growth, that is overcompensation, with improved apparent digestibility coefficient, food conversion efficiency and energetic efficiency into growth. This technique would be more practically applicable in indoor culture for this species.