Study of growth rate, nutritional indices and stress response in Pacu, Piaractus brachypomus, to produce edible fish

The main aim of this research is study of growth، survival، nutritional indices and stress response of P. brachymous in rearing conditions in a recirculation system. An experiment carried out in 3 recirculation treatments with 3 replications in 250-liter tanks with a volume of 200 litres water. An extra 100-liter tank prepared as biological filter. Tanks were stocked in 3 densities 50، 75 and 100 fingerling. m-3 with an average weight as 3. 52±0. 11 for duration of 3 months. Water replacement was 10% per day. Survival was determined with counting of dead fish daily and growth with monthly biometry. Blood was collected to determine cortisol and glucose as stress response indices. The results showed that intensity of 100 pis. /m3 has a negative effect on some of the growth indices: average of body weight، absolute growth rate، and daily gained weight (P<0. 05)، but no effect on Specific Growth Rate (SGR)، Relative Growth Rate (RGR) and Condition Factor (CF) (P>0. 05). In addition، the intensity 100 pi/m3 has negative effect on nutritional indices; FCR، protein production value، fat production value (P<0. 05). This stocking increased cortisol and glucose values in the fish (P<0. 05). It is concluded that since the intensity 100 pi/ m3 decreased the gain weight and increased stress responses in Pacu fish، it is suggested that 75 pi/m3 is the best intensity to produce edible fish with the defined experiment.