Effects of ration size and temperature on growth and metabolic parameters of juvenile noble crayfish Astacus astacus L.

A laboratory experiment was carried out to test the combined effects of ration size [1 vs 3% body weight (b.w.)] and temperature (15\ub12 vs 22\ub12\ub0C) on growth and metabolic parameters of 80 juvenile noble crayfish (Astacus astacus L.). The maximum daily consumption (C, g\ub7g-1) and respiration rate (R, g O2\ub7g-1\ub7d-1) were used to calculate the growth scope (i.e. the difference between maximum daily energy consumption and energy costs at a given temperature). The conversion of C and R into a food-equivalent unit (g food\ub7g-1\ub7d-1) allowed their comparison. Results showed that crayfish grew faster when fed 3% b.w. while temperature seemed to play a less relevant role on growth variables, affecting the moulting frequency only. Crayfish A. astacus fed ad libitum showed a relative insensitivity of the metabolic parameters (oxygen uptake, R and C) within the analysed range of temperatures, possibly reflecting its distribution across a broad variety of habitats with different thermal regimes. In the present study, A. astacus displayed some characteristics specific of a K-selected species, such as slow to moderate growth and low juvenile survival rate