Growth model for Atlantic cod (Gadus morhua): Effects of temperature and body weight on growth rate

Results from several laboratory experiments showed that at each temperature there was a linear relationship between the logarithms of specific growth rate (G%/day) and body weight (W g) of Atlantic cod fed to satiation: lnG = α + βlnW. Both α and β were found to be a function of temperature (T °C): α = a + bT + cT2; β = d + eT; a = − 0.7620, b = 0.3982, c = − 0.0128, d = − 0.1500, e = − 0.0239. The e-parameter was altered by 10% from the laboratory value (to e = − 0.0215) to tune the model in accordance with growth rate of large cod reared in sea cages in Norway. The model predicts that the optimal temperature for growth (Topt.G) declines with body weight: Topt.G =  15.57–0.8426lnW, i.e. 15.0, 13.0, 11.1 and 9.2 °C for 2, 20, 200 and 2000 g fish, respectively. The predicted growth rates at optimal temperature (Gmax) were 7.41, 2.62, 1.02 and 0.44%/day for 2, 20, 200 and 2000 g fish, respectively. Model calculations show that 30 g cod juveniles stocked in sea cages on 15 May have reached 1.6 and 2.1 kg by the end of the second year and 4.6 and 6.3 kg by the end of the third year, in Northwest Iceland and West Norway, respectively.