Reuse of Low-Salinity Water in Biofloc Systems for the Culture of Penaeus vannamei: Impacts on Water Quality and Zootechnical Performance
Author: Andrei Basilio Dias (Currículo Lattes)
Advisor: Dr. Wilson Francisco Britto Wasielesky Junior
Abstract
The Pacific white shrimp, P. vannamei, leads global crustacean production, with shrimp farming being a high value-added activity within Aquaculture. Due to its biological characteristics, such as high growth rates and tolerance to low salinities after acclimation, P. vannamei stands out in farming carried out in low-salinity inland regions. In this context, with the aim of adding sustainability to farms distant from the sea, the Biofloc Technology System (BFT) proves to be a promising technology, since at high salinities, water reuse is a technique successfully applied, allowing for a reduction in water usage and mitigation of the physiological effects caused by the accumulation of nitrogenous compounds in the water. In low-salinity conditions, these techniques need to be improved, especially to reduce transportation and water preparation costs, and to lower mortality rates caused by nitrite accumulation, which is the main factor responsible for mortality in such conditions. The objective of this study was to evaluate the reuse of different percentages of water containing mature bioflocs during the cultivation of P. vannamei juveniles (0.88g) in low-salinity conditions. The experimental design consisted of four experimental treatments defined according to different percentages of water reuse containing mature bioflocs from an ongoing cultivation, namely R0, in which organic fertilizations were carried out to develop bioflocs; R50 and R100, with 50% and 100% water reuse, respectively; and Clear Water, where no microbial floc development was stimulated, and no inoculum was added. P. vannamei juveniles were stocked at a density of 300 shrimp/m3 in 150L tanks, and water quality parameters, including ionic balance and zootechnical performance, were evaluated throughout the experiment. After 42 experimental days, water quality and ionic balance parameters showed optimal average values for P. vannamei farming, with significant differences between treatments in all analyzed variables except for dissolved oxygen, temperature, and magnesium. Zootechnical performance indices were more satisfactory in the Clear Water treatment, with significantly higher weekly growth rates, weight gain, final biomass, and productivity compared to the other treatments. The R0 treatment showed satisfactory zootechnical indices, with less additional water usage to maintain water quality, making it the most recommended treatment for farming P. vannamei at a salinity of 10 g L-1.