Effects of temperature on the growth of pollack (Pollachius pollachius) juveniles

Growth of juvenile pollack was assessed at five constant temperatures (9, 12, 15, 18 and 21 degrees C) in an 84-day trial. Duplicate groups of 75 fish (initial weight 143 +/- 2 g) were held in O-2 saturated water (102-103% saturation) and fed to apparent satiation. Growth increased as temperature increased from 9 degrees C up to a plateau at 12-15 degrees C (NS differences between 12 and 15 degrees C) followed by a decrease from 18 degrees C. No growth occurred at 21 degrees C. For the overall period, specific growth rates were 0.52% and 0.53% day(-1) at 12 and 15 degrees C compared to 0.40% day(-1) at 18 degrees C. Feed intake was maximum at 15-18 degrees C (0.68-0.69% day(-1)) and it was significantly lower at 21 degrees C (0.45% day(-1)). Apparent feed conversion ratio was significantly higher at 18 degrees C than at 12-15 degrees C (1.8 compared to 1.2-1.4). There was no significant change in fish whole body composition related to temperature. At the end of the experiment, fish growth recovery following a transfer from 18 and 21 degrees C to 15 degrees C was assessed using a 50-day challenge test. Growth rate of the previous 21 degrees C group was the same as in the 15 degrees C group (NS differences) and in the previous 18 degrees C group it was significantly lower. The study showed that pollack have a high capacity to recover from a prolonged period of low or no growth induced by high temperatures. (c) 2005 Elsevier B.V. All rights reserved.