The potential growth of salmonids

Abstract

The mean specific growth rates of live weight ( G) of brown trout and Arctic char in the man-made reservoir Nesjöen in Norway exceeded the established limits of maximum growth for all salmonids. Calculated for fish of unit weight (1 g), the values were 7.2 and 7.6% day −1 for the total growth season of the second year of the reservoir, and for 17 days of the third summer they reached 8.7 and 8.9% day −1 for brown trout and Arctic char, respectively. Temperature was limiting, and potential rates of 13.8 and 11.6% day −1 for fish of unit weight are predicted at optimal temperature. For sea-dwelling Arctic char a corresponding rate of 12.6% day −1 has been recorded by earlier workers. The following equations expressing the dependence of maximum growth on temperature, below the optimal ones, and fish size were derived: Brown trout; In G=In|13.8(-0.3474+0.1053T)|-0.325 In W Artic char; In G=In|12.6(-0.0815+0.917T)|-0.325 In W where G is specific growth rate of live weight (% day −1), T temperature (°C) and W fish weight (g). Such growth is dependent on a life in standing water, and the former lower limits of growth are assumed to be a consequence of experimental conditions and especially the effect of circulating or flowing water.