Live feed as supplement from the onset of external feeding of juvenile signal crayfish (Pacifastacus leniusculus Dana. Astacidae) under controlled conditions

Two 100-day experiments were carried out under controlled conditions in order to evaluate the effects of different combinations of a dry diet supplemented with live feed on survival and growth of juvenile Pacifastacus leniusculus Dana juveniles from the onset of external feeding. In the first experiment, juveniles were subjected to five feeding and density conditions: a dry diet for rainbow trout (D) with a density of 50 animals m− 2, the same dry diet supplemented with Artemia nauplii for 20, 60 or 100 days (50 m− 2) and D supplemented with Artemia nauplii for 100 days at a density of 200 m−2. When juvenile crayfish did not receive live feed supplement, mean survival rate (11.33%) and growth were significantly lower. The highest survival rates were obtained when nauplii were added for 100 days (57.83% and 57.33%). Survival rates in the two densities were similar but growth was significantly higher at the lowest one. When the period of supplementation was reduced to 20 or 60 days, survival rates decreased significantly. In experiment 2, amount and frequency of Artemia supply were increased and freshwater zooplankton (Daphnia pulex) was used as supplement of D. An increased frequency (three times a week) and amount of live food supply led to high survival rates (up to 82%) and growth (Carapace length: 11.79 mm, Weight: 360.16 mg). From these results it can be deduced that live feed can be the source of some nutritional factors needed for astacid juvenile crayfish from the onset of external feeding to guarantee the viability during the first months of life.