Influence of biofilm on the survival and growth of juvenile pink shrimp Farfantepenaeus paulensis cultivated in a nursery system in the Lagoa dos Patos estuary
A series of experiments was carried out to evaluate the influence of biofilm on the survival and growth of juvenile pink shrimp Farfantepenaeus paulensis grown in fixed cages in a shallow estuary in Lagoa dos Patos - RS - Brazil. The first experiment evaluated the ability to fix biofilm of six types of materials: green and white polyethylene mesh (1mm mesh), alignment bags of the type used for feed packaging, polyamide mesh (12mm mesh) and polyester coated mesh. PVC (1.5 and 5mm meshes). Panels of 1m2 of these materials were immersed in situ for 28 days and samples were taken weekly to estimate the amount of chlorophyll a.The final values found ranged between 3.68 and 9.34 mg / cm2 of chlorophyll a with polyethylene nets showing the greatest results.The second experiment evaluated the survival and growth of shrimp grown for 30 days in two treatments. Three cages were installed in the estuary 15 days before the start of the experiment's cultivation phase and biofilm fixation was allowed in them throughout the experimental period. Another three cages were installed on the day of storage of the shrimp (beginning of the cultivation phase) and were changed every ten days in order to limit the fixation of biofilm. At the end of the experiment, it was found that the shrimp grown in the cages where there was no limitation of biofilm fixation had significantly greater growth (p <0.05) compared to the other treatment. There was no significant difference in relation to survival in the two treatments (p> 0.05).The third experiment evaluated the effects of increasing the area for biofilm fixation on shrimp survival and growth. All cages were installed in the water 15 days before the beginning of the experiment's cultivation phase. In three cages, 8m2 of polyethylene screens were added. At the end of the experiment, it was found that the shrimp grown in the cages where extra substrates for biofilm fixation were placed had significantly higher survival and growth (p <0.05) compared to the other treatment. In the first and third experiments, the microbial composition of the biofilm was analyzed. The results of these experiments demonstrated the importance of biofilm and the use of extra substrates in the cultivation of F. paulensis juveniles in nursery systems carried out in the Lagoa dos Patos estuary.