Effects of temperature and body weight on growth rate and feed conversion ratio in turbot ( Scophthalmus maximus)

Abstract

Six size groups of hatchery produced turbot (2–499 g) were reared at six constant temperatures (10–25 °C). The results were used to develop a mathematical model for growth rate and feed conversion in turbot. At each temperature there were linear relationships between logarithms of (a) specific growth rate ( G%/day) and body weight ( W g), and (b) feed conversion ratio ( FCR) and W. The slopes of the regressions were linearly related to temperature and the intercepts of the regression changed with temperature according to a second order polynomial. The optimal temperature for growth ( T opt.G ) is predicted to decline with increasing body weight: T opt.G = 22.45 − 0.713ln W, i.e. 22.5, 20.8, 19.1 and 17.5 °C for 1, 10, 100 and 1000 g fish, respectively, and the growth rates of these fish sizes at their optimal temperature ( G max ) were predicted to be 7.63, 2.73, 1.03 and 0.40%/day, respectively. The optimal temperature for feed conversion ( T opt.FCR ) is also predicted to decline with increasing fish size: T opt.FCR = 18.80 − 0.625ln W, i.e. 18.8, 17.4, 15.9 and 14.5 °C for 1, 10, 100 and 1000 g fish, respectively, and the predicted feed conversions of these fish sizes ( FCR min ) were 0.44, 0.56, 0.68 and 0.82 for the present feed types. The growth model predicts that 2 g turbot can reach 743 and 619 g in 1 year when reared at T opt.G and T opt.FCR , respectively.