STANDARD EXPERIMENTAL DIETS FOR CRUSTACEAN NUTRITION RESEARCH .2. GROWTH AND SURVIVAL OF JUVENILE CRAYFISH ASTACUS-ASTACUS (LINNE) FED DIETS CONTAINING VARIOUS AMOUNTS OF PROTEIN, CARBOHYDRATE AND LIPID

Nutritional experiments were conducted with individual juvenile freshwater crayfish, Astacus astacus (Linne), using twelve pelleted diets containing various combinations of protein (22, 31 or 40%), lipid (5.5-16%) and carbohydrate (9.2-25.8%) in a 394-day experiment. The diets ranged from 241 to 321 kcal/100 g feed and with protein/energy (P/E) ratios of 69 to 153 mg/kcal. The experiments were carried out in a closed system with constant temperature; dissolved nitrogen, oxygen content, pH and water temperature were monitored. All diets with 40% protein gave a good survival rate. The diet with 31% protein, moderately high carbohydrate (16.6%) and a low lipid content (7%) promoted a high survival rate as well. At the 22% protein level, the feed with high lipid content (16%) gave a poor survival rate. The mean biomass increase was greatest with all diets with 40% protein and those diets with 31% protein, high carbohydrate level and low lipid content. Younger juveniles demonstrated the highest growth rate on 40% protein diets and 31% protein diets, when the latter contained P/E ratios in the range 114 to 153 mg/kcal. At the 22% protein level growth was poor. Optimum biomass gain was obtained with P/E ratios above 114 mg/kcal. Optimum lipid/carbohydrate ratios changed with protein content of the feed. Lipid levels above 10% in diets containing 31 and 22% protein depressed the growth rate of younger animals. With increasing physiological age, the animals responded favourably to higher lipid and carbohydrate levels.