Effect of periphyton on microbial dynamics, immune responses and growth performance in black tiger shrimp Penaeus monodon Fabricius, 1798

To evaluate the effect of periphyton, an on-station grow out trial was conducted for 130 days with tiger shrimp, Penaeus monodon @ 8 nos. m-2 in zero water exchange ponds. Bamboo poles (1.8×0.06 m) were fixed @ 2000 nos. ha-1 in treatment ponds for periphyton development. Total bacterial count (TBC) in water was significantly lower (p<0.05) in periphyton based ponds (83.50±11.86×103 CFU ml–1) compared with control (288.00±90.15×103 CFU ml–1). The total Vibrio count (TVC) in water had similar pattern which was 35.3% lower in treatment group compared to control. The TBC and TVC in periphyton biomass over the submerged substrate were 333.13±114.14×106 CFU g-1 and 151.88±26.37×103 CFU g-1 respectively. At the end of the culture period, higher haemocyte count (p<0.05) (10.83±0.71×107 cells ml–1) and prophenol oxidase activity (p<0.05) (8.65±0.47 U) was recorded in treatment ponds compared to control (9.38±0.47×107 cells ml-1 and 5.18±0.51 U). In pathogen clearance test, treatment group recorded significant reduction (p<0.05) of Vibrio harveyi , 3 h post-inoculation. At the end of the trial, 17.90% gain in production and 22.29% reduction in FCR was observed in periphyton group compared to control.