Efeito da densidade de adição de Brachionus plicatilis no cultivo de pós-larvas de Litopenaeus vannamei em sistema de bioflocos

Abstract

The production of juvenile marine shrimp has used strategies that involve coexistence with pathogens, reducing production losses in shrimp farming. One of these strategies is the application of microorganisms that can improve the nutritional content of microbial biofloc in the early stages of cultivation, contributing to greater growth of shrimp and stronger immune systems. This study evaluated the effect of addition of the rotifer Brachionus plicatilis at different densities to the cultivation of post-larvae Litopenaeus vannamei in a biofloc system supported by fermented base with a mix of bacteria. The experimental design consisted of four treatments with three replicates of each, generating a total of 12 experimental units in a completely randomized design for 42 days. The treatments iuncluded: BFT (Bioflocs); BFT - 10 (Bioflocs with the addition of B. plicatilis at a density of 10 organisms mL-1), BFT - 20 (Bioflocs with the addition of B. plicatilis at a density of 20 organisms mL-1) and BFT - 30 (Bioflocs with addition of B. plicatilis at a density of 30 mL-1 organisms). Ten-day-old postlarvae (PL10) with an average weight of 3.4 ± 0.02 mg were stocked at a density of 3,000 individuals m-3 in experimental units of 40L of useful volume. The rotifer B. plicatilis were added on the 1st, 10th, 20th and 30th days. The shrimps were fed with a commercial ration with 45% crude protein, four times a day with an initial feed rate of 35% of the biomass. During the experiment, we evaluated the water quality, zootechnical performance, and monitored the zooplankton community, centesimal composition, total hemocyte count, and quantified and characterized the Vibrio bacteria. The water quality variables were within the recommendations for marine shrimp and no significant differences were observed between treatments. At the end, regarding zootechnical performance, the highest average values of final weight and productivity were in treatments with the addition of B. plicatilis, in which the shrimp reached 1.09 to 1.26 g and 2.25 to 3.41 kg m-3. The most frequent phytoplankton genera observed were: Oscillatoria (6.97 to 9.27%), Aphanocapsa (6.48 to 7.85%), and for and zooplankton were: Brachionus sp. (21.49 to 33.73 %), Daphnia sp. (15.44 to 31.25%) and Arcella sp. (12.75 to 20.62%). The