THE GROWTH AND FOOD RATION OF PISCIVOROUS BROWN TROUT (SALMO-TRUTTA)

1. In this study we examined how temperature, a major determinant of energy budgets and thus the biological success of ectothermal animals, affects growth and feeding rate of a teleost fish species. 2. Feeding experiments with piscivorous brown trout from the Norwegian River Laerdalselva were performed in the laboratory at water temperatures from 8 to 18-degrees-C, to estimate the optimal temperature for growth fed at maximum rations. 3. Optimal temperature for growth was found to be approximately 16-degrees-C, which is 2-4-degrees-C higher than reported previously. 4. In contrast to earlier studies, the optimal temperature for growth was similar to the temperature at which maximum feeding rates occurred. 5. Growth increased more rapidly with increasing temperature for small and young fish than for large and old fish.