Influence of raceway based biofloc system on the growth and physiological responses of Penaeus vannamei and GIF tilapia in a polyculture model - BFT aquaculture system

The present study investigates the efficiency of raceway-based biofloc technology for the production of Penaeus vannamei and Genetically Improved Farmed tilapia in a polyculture model. Six raceway tanks were used to explore the growth performance, digestive enzyme activities, bacterial count and histology of P. vannamei reared with GIF tilapia using raceway-based biofloc and clear water raceway culture systems. Each raceway (6.8 m x 2.2 m x 3 m) was stocked with 60 shrimp/m(3) of P. vannamei (0.93 +/- 0.09 g), and 5 fish/m(3) of GIF tilapia (0.42 +/- 0.01 g) and reared for 90 days. Biofloc, with a carbon: nitrogen ratio of 15:1, is developed and maintained using soyahull pellet powder as organic carbon source, with continuous aeration was provided. The present study found significantly higher weight gain of P. vannamei (16.09 +/- 0.26 g) and GIF tilapia (11.71 +/- 0.35 g) in raceway-based biofloc culture system. Survival of P. vannamei and GIF tilapia did not exhibit any significant variations between raceway-based biofloc and clear water raceway systems. Significantly higher digestive enzymes activities of protease (0.25 +/- 0.01 and 0.14 +/- 0.02 U/ mg protein/min), lipase (0.88 +/- 0.04 and 0.37 +/- 0.01 U/ mg protein/min) and amylase (0.008 +/- 0.00 and 0.0016 +/- 0.00 U/ mg protein/min) are recorded in P. vannamei and GIF tilapia in raceway-based biofloc culture system, respectively. Higher values of total heterotrophic bacteria (52.25 +/- 0.88x10(4) CFU/ml, 49.63 +/- 1.10 x10(7) CFU/g and 53.12 +/- 0.44x10(7) CFU/g) and bacillus counts (76.50 +/- 0.46x10(2) CFU/ml, 155.62 +/- 0.89x10(2) CFU/g and 238.75 +/- 0.82x10(2) CFU/g) are recorded in culture water, P.vannamei gut and GIF tilapia gut in raceway based biofloc culture system, respectively. No histopathological changes are observed in the GIF tilapia (gut), P. vannamei (gut and hepatopancreas), but deformities such as congestion of the tips of few secondary lamellae are noticed in the GIF tilapia (gill) reared in the clear water raceway system. Therefore, the study suggests that polyculture of P. vannamei and GIF tilapia in a raceway-based biofloc system is advantageous over the clear water raceway system in terms of production augmentation with improved physiological conditions.