Effect of stocking density of Crassostrea sp. in a multitrophic biofloc system with Litopenaeus vannamei in nursery

In recent years, the coculture of organisms from different trophic levels has been practiced to improve water quality and nutrient consumption. In this context, this study evaluated the effect of Crassostrea stocking density on zootechnical performance and water quality of Litopenaeus vannamei reared in a multitrophic biofloc system during the nursery phase. The experimental design was completely randomized with four treatments: control (shrimp monoculture) and three treatments with oysters (3.21 +/- 1.26 cm) at densities of 100, 200 and 300 oyster m(-2), for 45 days. Water quality, zootechnical performance parameters of shrimp and oysters, proximate composition of microbial flocs, Vibrio count from water, shrimp and oysters samples and total hemocyte counts from shrimp and oyster samples were evaluated. For water quality, multitrophic biofloc system treatments had the lowest amounts of settleable solids, resulting in lower settling chamber use than the control. However, a high density of oysters (300 oysters m(-2)) increased total ammonia nitrogen and nitrite-N levels, which had maximum values of 4.01 and 4.63 mg L-1, respectively. The final average weight and cumulative growth of oysters were 16.23 +/- 3.45 g and 18.91 +/- 5.24%, respectively, corresponding to an average growth of 4.07 +/- 0.34 mm month(-1). In shrimp performance, the higher density treatment (300 oysters m(-2)) had the lowest values of final weight and yield (0.94 +/- 0.03 g and 2.26 +/- 0.05 Kg m(-3)) and the lowest nutritional quality of the microbial floc (14.96% protein and 3.71% lipid). The Vibrio count was significantly lower in all the multitrophic biofloc system treatments compared to the control, with an average reduction of 37.32% in water and 75.69% in shrimp hepatopancreas. Stocking densities of up to 200 oysters m(-2) did not affect shrimp growth in the multitrophic biofloc systems evaluated. The multitrophic biofloc system used in this research is a viable option for controlling nitrogen compounds and solids and reducing Vibrio in a shrimp biofloc system during the nursery phase.

Automated summary

The study evaluated the impact of Crassostrea stocking density on the zootechnical performance and water quality of Litopenaeus vannamei reared in a multitrophic biofloc system. High oyster density increased ammonia and nitrite levels, leading to reduced shrimp yield and nutritional quality. The system effectively controlled nitrogen compounds and solids, and reduced Vibrio in a shrimp biofloc system during the nursery phase.