Fisheries Institute in Olsztyn, Poland Citation: Bhatnagar A., Dhillon O. 2019 -Characterization, screening, and application of bacteria with probiotic properties isolated from the gut of Labeo calbasu (Hamilton) -Fish. Aquat. Life 27: 178-189.Abstract. Labeo calbasu is not reared in aquaculture because of the unavailability of proper feed and the risk of infection. The ability of probiotics to promote growth and immunological defense barriers in the gut has led to the use of autochthonous probiotic bacteria. Hence, the present study was conducted to screen potential probiotic bacteria from the gut of L. calbasu and to supplement the same to study the effect on growth and immunity. Strains with probiotic properties were assayed for exogenous enzyme production and identified based on phylogenetic analysis and nucleotide homology. Four of nine isolates showed promising antibacterial activity against Aeromonas hydrophila. The strains survived in relatively low pH and high bile concentrations and were investigated for hydrophobicity, autoaggregation, and coaggregation. Based on the positive results of this study, the LC1 and LC4 strains (analysed with 16S rRNA gene sequencing and showing similarity with Aneurinibacillus aneurinilyticus and Stenotrophomonas sp.) were further incorporated into diets to explore their probiotic effects on the growth performance and immunity of the fish. Administering the probiotics elevated growth parameters and benefitted the immune system by increasing the phagocytic index and decreasing the mortality rate with exposure to A. hydrophila.

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Integrating fish and paddy culture may enhance the production with maintaining equitable use of the available land and human resources to ensure global food security. Hence the present study has been carried out to explore the possibility of culture of fish, Channa punctatus in paddy fields with/without supplementary feed. Four treatments (T1: No fish, no pesticide in paddy fields; T2: Fish in paddy fields without pesticide exposure; T3: Fish in paddy fields with are commended dose of pesticide and T4: Fish in paddy fields with pesticide dose as per farmers) were maintained in both experiments (with/without supplementary feed) in 120 m2 paddy plots. Farmers’ treatment without fish was also considered (T5). Fingerlings (15.50±0.40 g) were stocked with 1 fishper 3m2. Water quality, growth performance, carcass composition, paddy yield and economics were studied. Water quality remained in the optimum range for fish culture (D.O. 4.-7.1 mg l-1, pH 7.5-8.8).Growth performance and carcass composition revealed significantly (P<0.05) higher valuesin T2(SGR: 52.03, 129.73; crude protein: 14.8%, 15.0%). The values for paddy productions and economics increased from T1(24±0.326 q ha-1 and INR 32,850.00) to T3(55±0.475 q ha-1and INR 111,672.00), decreased thereafter. Results of supplementary food experiments clearly revealed that although fish growth/yield was higher in T2 (659±0.514 kg ha-1), rice production per hectare (57±0.891 q ha-1) and net revenue gain (INR 237,457.00) was high in T3 with recommended pesticides use. Thus, fish-cum paddy culture can yield economic benefits contributing significantly towards sustainable food security.

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