Temperature dependency of early growth of turbot ( Scophthalmus maximus L.) and its implications for developmental progress

Growth in developing turbot larvae can be expressed independently of temperature when using effective day-degrees ( D° eff) as an index of development. The calculation of D° eff is based on the principle of thermal summation whereby the rate of development is linearly related to the ambient temperature above a species-specific threshold temperature ( T 0) at which development is theoretically arrested. The T 0 for turbot embryos is 5.3°C. The increase in wet body mass of developing turbot larvae at 14, 18, and 22°C can be aligned into a single exponential relationship regardless of incubation temperature when using D° eff as the index of development. Previous attempts to relate physiological processes in poikilothermic animals, including fish, to incubation temperature are discussed.