Performance of white shrimp (Litopenaeus vannamei) grown in diatoms or microbial flocs with minimal water exchange

Author: Leandro Cesar de Godoy (Currículo Lattes)
Supervisor: Dra Clarisse Odebrecht
Co-supervisor: Dr Wilson Francisco Britto Wasielesky Junior

Abstract

The present study aimed to determine the efficiency of media containing diatoms or microbial flocs and the mixture of both, in the survival, growth and feed conversion of juvenile white shrimp (Litopenaeus vannamei) in super-intensive cultivation with minimal water exchange. For 30 days, prawns with an initial average weight of 0.31 ± 0.10 g were grown in 12 80 L tanks (called microcosms) at a density of 300 prawns/m2 in 3 treatments with 4 replicates. In the treatment in the midst of diatoms (MD) the water came from a matrix inoculated with the species Thalassiosira weissflogii and Chaetoceros muelleri. In the treatment in the midst of microbial flocs (MF) the matrix received an organic fertilization daily maintaining the C/N ratio in the middle of approximately 17: 1.The mixed treatment (MM) consisted of a matrix that received water from MF and MD in an equal proportion (1: 1). A recirculation system was used so that the water from the matrices was pumped through submerged pumps to the respective microcosms, and returned by gravity. Water quality parameters were monitored and samples collected every 3 days were used to quantify and characterize the microbial community present in the treatments. The physical-chemical parameters of the water were within the recommended range for the good performance of the species. The shrimps grown in the MD had a significantly higher final weight (P <0.05) compared to the other media. The feed conversion rate was lower in the DM (0.47), not differing significantly from MM and MF (0.76 and 0.80 respectively).Survival was high (90 - 97%) and there was no significant difference (P> 0.05) between treatments. A variety of protozoa, some metazoans, microalgae and cyanobacteria were observed, reflecting the diversity of trophic levels present in the water for cultivation of the three treatments. Filamentous cyanobacteria and especially colonies of coccoid cyanobacteria seem to have great importance in the formation of microbial flocs. The results indicate that the natural food was of great importance for the performance of the shrimp in all treatments and that the diatoms served as a source of essential nutrients that contributed significantly to the better performance of the shrimp in the MD treatment

 

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