THE CULTURE OF THE PACIFIC WHITE SHRIMP Litopenaeus vannamei WITH LIGHT RESTRICTION REARED IN BFT SYSTEMS

In recent years, new management practices have been studied for production of food shrimp with emphasis on reduced water exchange. The biofloc technology culture system (BFT) contributes to the water quality, through the removal of nitrogen compounds, supplements the shrimp diet and allows the use of high stocking densities. In this system, in this system They may occur changes in water when exposed to long periods of solar insolation changing from a system with green water, to a brown water system, and vice versa. The present study aims to evaluate the bacterial community and zootechnical performance of Litopenaeus vannamei in tanks with light restriction in a biofloc system.

A 70 day-trial was conducted at the Marine Station of Aquaculture, University of Rio Grande, Rio Grande do Sul State, Brazil. After nursery, Pacific white shrimp (1.06g ±0.58) juveniles were stocked at 400/m³ in a nine-35 m³ lined raceways greenhouse enclosed. Three treatments (three replicates) were tested: T1, 24 hours night; T2, 24 hours day, and T3 12 hours night and 12 hours day.  Shrimp were fed with a commercial diet (42% CP, 0.4-1.2mm, Guabi®, Campinas, SP, Brazil), offered on a feed tray (10 cm diameter, 5 mm mesh size, one per tank). At study initiation shrimp were fed 50% their total biomass. Daily rations were adjusted based on shrimp consumption and growth performance. Tanks were kept with no water exchange through the duration of the study. Water temperature, salinity, dissolved oxygen (DO) and pH was recorded twice daily (0800 and 1700) using a YSI 556 MPS meter (YSI Inc., Yellow Springs, Ohio, United States). Water was tested daily for for measuring TA-N. Monitoring of NO₂-N, NO₃-N and PO4⁺³-P was done every five days, while alkalinity was measured once a week. Adjustments of culture water pH in all test-tanks were made anytime the levels dropped below 7.2 using 0.05 g of Ca(OH)₂ for each liter of water (added directly into water). Water turbidity was measured once a week using a Turbidimeter (Hach 2100P, Hack Company, Loveland, Colorado, United States). Total suspended solids (TSS) and settleable solids (SS) were measured three times per week. Every week, 60 shrimps were randomly sampled from each tank and individually weighed. At the end of the trial, total shrimp biomass along with individual weights of randomly selected 200 shrimp from each tank were recorded. Water quality parameters were compared by two-way repeated measures ANOVA (system type). Significant differences of P<0.05 was used in all zootechnical performance, Tukey's multiple-range test was applied when significant differences were detected. At this time the study is currently underway and this presentation will summarize the results obtained in this study.