Influence of in situ Biofloc Production on Bio Growth Performance, Physiological Immune Response, Digestive Enzyme Activity, Nutrient Composition and Disease Resistance of Etroplus suratensis

The present experiment was conducted to investigate the effects of in situ jaggery based biofloc on bio growth performance, physiological immune response, digestive enzyme activity, nutrient composition and disease resistance of Etroplus suratensis.

The fingerlings of pearlspot, E. suratensis with an average body weight of 5.67±0.08 g was stocked at the rate of 150/m³ in treatment and control system. The in situ biofloc was produced in 2.4-ton capacity outdoor tanks using jaggery as carbon source at two different C:N ratio viz, 10: 1 (B1) and 20:1 (B2), where clear brackishwater system and without carbon sources as control.

The levels of ammonia nitrogen, nitrite-nitrogen and nitrate-nitrogen were reduced in the in situ biofloc compared to control while TSS and TS were increased significantly in all in situ biofloc compared to control. The physiological immune responses such as respiratory burst test, myeloperoxidase, serum lysozyme and antioxidant enzymes activity, superoxide dismutase and catalase were found to be significantly higher in B2 at end of the trial. Stress parameters glucose and cortisol were significantly lower in jaggery based biofloc system especially in (B2) C: N 20:1 compared to control. The fishes from the jaggery based biofloc groups possessed significantly (P<0.05) higher immune status as compared to control. The digestive enzymes activity such as amylase protease and lipase, of fish was higher in biofloc treatment and lower in control. Compared to control the nutrient composition of E. suratensis was significantly higher in the treatment groups. Moreover, jaggery based in situ fishes showed lower cumulative mortality rate and enhanced relative levels of protection after experimental challenge with A. hydrophila compared to control.