Water quality, Vibrio density and growth of Pacific white shrimp Litopenaeus vannamei (Boone) in an integrated biofloc system with red seaweed Gracilaria birdiae (Greville)

An indoor trial was conducted for 42days to evaluate water quality, Vibrio density and growth of Litopenaeus vannamei in an integrated biofloc system (IBS) with Gracilaria birdiae. Four treatments were used, each in triplicate: Control (monoculture shrimp); IBS 2.5 (L.vannamei and 2.5kg wet weight seaweedm(-3)); IBS 5.0 (L.vannamei and 5.0kg wet weight seaweedm(-3)) and IBS 7.5 (L.vannamei and 7.5 wet weight seaweedm(-3)). Shrimp individuals (0.34 +/- 0.01g) were stocked at a density of 500 shrimpm(-3). No water exchange was carried out during the experimental period. Molasses was added once a day as an organic carbon source to maintain the C:N ratio at 12:1. The IBS significantly decreased (P<0.05) dissolved inorganic nitrogen (DIN) ranging from 19% to 34% (3.12-3.83mgL(-1)), NO3-N ranging from 19% to 38% (2.40-3.16mgL(-1)), Vibrio density ranging from by 8-83% (0.40-2.20 log 10(3) colony-forming unitsmL(-1)), and FCR ranging from by 20-30% (1.20-1.37), as compared to the control (4.73mgL(-1), 3.93mgL(-1), 2.40 log 10(3) colony-forming unitsmL(-1), and 1.74 respectively). Moreover, the IBS significantly increased (P<0.05) crude protein in whole body shrimp, ranging from 8% to 13% (13.2-13.7% wet weight basis); as well as final weight, ranging from 25% to 32% (3.90-4.12g), weekly growth ranging from 25% to 34% (0.59-0.63g), and shrimp yield by 22-39% (1.72-1.96kgm(-3)), as compared to control (12.1% wet weight basis, 3.12g, 0.47g, and 1.41kgm(-3) respectively). It can thus be concluded that cultivating Gracilaria birdiae in an IBS with L.vannamei can contribute to DIN and NO3-N removal, lower Vibrio density, increased crude protein in whole body shrimp, higher growth and yield parameters in shrimp culture.