Gabriele Lara

NURSERY OF LITOPENAEUS VANNAMEI REARED IN A BIOFLOC SYSTEM: THE EFFECT OF STOCKING DENSITIES AND COMPENSATORY GROWTH

ABSTRACT The purpose of this study was to evaluate the effect of stocking density and the occurrence of compensatory growth in the white shrimp Litopenaeus vannamei in the nursery phase reared in a biofloc culture system. Two experiments were performed in a recirculating water system with 12 experimental tanks (microcosm), each with a bottom area of 0.5 m2. The tanks were supplied by a matrix 70-m2 biofloc technology water tank (macrocosm), where a shrimp biofloc technology systems culture was maintained concurrently. The water was returned to the system by gravity, providing a daily renewal rate of approximately 4,800%. During the first experiment, L. vannamei postlarvae with an initial weight of 0.003 g were cultured for 30 days at densities of 1,500, 3,000, 4,500, and 6,000 shrimp/m2. The cultures reached significantly different final weights (P < 0.05) of 0.45 g, 0.33 g, 0.30 g, and 0.23 g, respectively. Mean survival rates were greater than 87.6% in all treatments. To evaluate the occurrence of compensatory growth in L. vannamei after a period of enclosure stress, the second experiment was organized in 2 phases. During the first, shrimp postlarvae were reared at densities of 1,500, 3,000, 4,500, and 6,000 shrimp/m2 for 35 days. The shrimp were then restocked at a density of 300 shrimp/m2 and were maintained until compensatory growth was observed. In 20 days, the shrimp showed full compensatory growth. The mean final weight and survival rate did not differ significantly (P > 0.05) between the treatments. The results confirm that the strategy of enclosure rearing can be applied to the culture of L. vannamei.

The Effect of Probiotics in a Litopenaeus vannamei Biofloc Culture System Infected with Vibrio parahaemolyticus

We analyzed the effect of commercial bacterial probiotics on a Litopenaeus vannamei biofloc culture system infected with Vibrio parahaemolyticus. Three replicates of two experimental treatments were conducted: a control system (without probiotic) and a system with the application of a multistrain probiotic containing Bacillus spp., Enterococcus spp., Thiobacillus spp., and Paracoccus spp. applied to the water and another multistrain probiotic containing Bacillus spp., Enterococcus spp., and Lactobacillus spp. added to the feed. Growth and survival rate were significantly higher in the probiotic treatment group (P < 0.05), and the shrimp in the probiotic group also had a lower (P < 0.05) FCR compared to the shrimp in the control group (1.4 vs. 2.7).

The use of different aerators on Litopenaeus vannamei biofloc culture system: effects on water quality, shrimp growth and biofloc composition

This study evaluated the effects of different aeration types on water quality, shrimp growth and biofloc composition in a Litopenaeus vannamei culture. The study was conducted with three treatments: (1) PR—propeller aspirator pump aerator; (2) VP—vertical pump aerator; and (3) BL—diffused air blower. The study was performed in a greenhouse with nine 35,000-L rectangular tanks. Water quality parameters (temperature, salinity, dissolved oxygen, pH, ammonia, nitrite, nitrate, settleable and suspended solids) were measured along the 33 experimental days. Moreover, samples were collected to quantify the microorganisms present in the tanks. At the end of the study, samples of the biofloc of each tank were collected to proximal analysis. Throughout the experiment, the temperature, pH, salinity and alkalinity were maintained within the recommended levels for L. vannamei. The propeller treatment showed a concentration of total ammonia above the recommended levels and lower densities of ciliates and flagellates, most likely because of inadequate biofloc formation in this treatment. The final weight was higher in the blower and propeller treatments. However, survival was lower in the propeller treatment compared to the other treatments. The results of this study suggest that diffused air systems (air blower) improve the formation of biofloc and growth performance of L. vannamei.

Long term storage and the compensatory growth of white shrimp Litopenaeus vannamei in aquaculture ponds

Effects of shrimp confinement in a situation of high density stocking in a long term nursery on their growth performance in grow out ponds. Were analized two nurseries with a density of 2000 shrimp m -2 were stocked at two different times. The first nursery (LTN) lasted 144 days, and the SGR of the animals was 3.0% day -1 . The second nursery (STN) lasted 18 days and the specific growth rate (SGR) was 19.9% day -1 . On the same day, shrimps were transferred to six lined ponds at a density of 20 shrimp m - ² where they remained for 101 days. In the first biometry, the SGR in the LTN treatment, increased to 6.7% day -1 and in the STN it decreased to 5.0% day -1 . At the end, shrimps of the LTN and STN treatments reached weights of 8.46 and 6.72 g and had productivities of 1287 and 1015 kg ha -1 , respectively. Shrimps reared in nurseries for long periods showed growth and survival rates similar to those obtained using conventional management practices in grow out structures.