Influence of stocking density on the performance of white shrimp Litopenaeus vannamei during the final fattening phase in a super-intensive system
The present study aimed to evaluate the influence of stocking density on the growth and survival of Litopenaeus vannamei shrimp sub-adults, grown in a super-intensive system without water renewal with the presence of microbial flocs. For this purpose, in a closed greenhouse, a system was set up containing 12 tanks (called microcosms) where they were grown for 45 days of juvenile L. vannamei with an initial average weight of 11.96 ± 1.14g. The prawns were stocked at densities of 150, 300, 450 and 600 m-2 prawns with 3 replicates per treatment. Artificial substrates were placed in the experimental tanks for the growth of the biofilm. The air supply and water circulation occurred through a 4.5 CV blower, the water was pumped to the experimental units, at a flow of 6,6 L / min per experimental unit, which was equivalent to 48 recirculations of the total volume of water per day. The water exit was by gravity, through a chute that directed it to a tank (matrix of flocs) in a “raceway” system. In the flake matrix, two months ago, there was a super-intensive cultivation without water renewal, of L. vannamei at the stocking density of 300 shrimp m-2. The suspended material (microbial flocs) was collected for analysis of proximal composition. The growth of the shrimp was analyzed through biometrics and at the end the shrimp were counted to verify the survival in the different densities. The stomach content of the shrimp in the different treatments was analyzed at the end of the experiment. The water quality parameters of the flake matrix were monitored daily.The main microorganisms present in the biofilm that formed on artificial substrates and in the matrix tank were identified and quantified, as well as chlorophyll a and dry weight were quantified. In the analysis of microorganisms, a preference was mainly for shrimp to consume rotifers, ciliate and flagellates. A negative relationship was observed between the increase in the stocking density of shrimp and their survival and growth. The results show that the recommended stocking density for the cultivation of L. vannamei final fattening phase in the proposed system should be between 300 and 450 shrimp m-2.