To investigate the effects of Bacillus subtilis as water additive on gut microbiota in Spinibarbus caldwelli, Acrossheilus hemispinus and Hypophthalmichthys molitrix and its purification effect on aquaculture water, the gut microflora in the foregut, midgut and hindgut of three fishes were investigated through 16S rDNA sequencing and the pH, the levels of ammonia nitrogen and nitrite in the aquatic water were measured. The results suggested B.subtilis could reduce the contents of ammonia nitrogen by 46.39% in water stably since the 11th day and nitrite by 84.61% in water stably since the 19th day. The gut microflora in each intestinal site between experiment and control group were significantly different overall and the abundance of intestinal flora decreased in the experiment group. On the whole,in experiment group, the abundance of intestinal microbiota decreased and the phylum abundance of Actinobacteria and Planctomycetes increased and decreased, respectively. The genus levels of Bacillus increased while pathogenic bacteria Aeromonas and Vibrio decreased. The KEGG signal pathways showed that the metabolic functions of the H.molitrix were enhanced. This study showed that B.subtilis could reduce the level of ammonia nitrogen and nitritein in the aquatic water and purify the aquatic wate, while inhibiting the propagation of harmful intestinal microbiota and improving the metabolic level of intestinal microbiota in H.molitrix.

With the gradual rise of aquaculture of Mastacemblus armatus,the problems such as germ plasm confusion and unclear genetic background have become increasingly prominent,which are not conducive to the commercial development of variety.In order to explore the breeding potential of M.armatus,this study used wild M.armatus as parents to construct 17 full-sib families through full-sib breeding model.After 18 months of cultivation,seven effective families were finally obtained.The single trait animal model was used to estimate the breeding value and heritability of each individual by BLUP,with the average body weight of each family as a covariate.The variance component evaluation results of the full-sib family weight of 18 pfm M.armatus showed that the heritability was(0.468 1±0.173 7),the t test reached P<0.01,and the body weight had a positive correlation with breeding value.The regression equation of male was y=0.393 6x-84.193 0(R²=0.755 4,P<0.01);the female was y=0.517x-64.126(R²=0.817 8,P<0.01).The females with the top 50 breeding values were mainly concentrated in family B,E and D,especially family B,the top 24 females and top 19 males were from this family.The maximum breeding value of male fish was 75.09,and that of female fish was 67.49,both of them were from the same family B.Through this study,the M.armatus had high heritability of body weight,which could be selected by phenotype or BLUP breeding value.