Effects Of Effective Microorganisms Supplementation And Polyculture Mode On Growth Function,Muscle Quality And Water Microflora Structure Of Micropterus Salmoidesunder

Micropterus salmoides,also known as California bass,has been introduced to my country since the 1970s.After years of research and breeding,it has become an important freshwater fish in my country.In recent years,in order to reduce environmental pollution,various places responded to the policy of removing cages.Yields have suffered,so largemouth bass farming models are at a critical point in need of adjustment.This study intends to explore the green ecological culture mode of largemouth bass through the application of EM（Effective Microorganisms）and the method of polyculture of crab and perch.A total of 4 breeding groups were set up in the experiment.Group（ML）,EM single-breeding perch group（EL）and single-breeding perch group（L）,each group was set with3 replicates,and the experimental period was 180 d.By measuring the water quality of aquaculture water,the growth of Micropterus salmoides,antioxidant,immunity,muscle quality and other indicators,in order to provide scientific reference for the promotion of the green ecological high-quality breeding model of Micropterus salmoides.1.Effects of effective microorganisms（EM）on water quality and microbial communities in Micropterus salmoides culture High throughput sequencing results of 16S r RNA gene showed that the main dominant bacteria were Bacteroides,Proteobacteria,Actinomycetes and Cyanobacteriam during the experiment period.furthermore,in period III and IV,Bacteroides was the highest abundance bacteria in the EL group with 42.07%and 38.52%respectively,while Actinomycetes had the highest abundance respectively with 71.83%and 31.37%in the L group.The abundance of cyanobacteria was higher in the early stage of culture in EL group,but less than 1%in the later stage（period III and IV）,while in L group,the abundance of cyanobacteria was more than 1%in the whole periods;the relative abundance of mycobacteria in EL group was significantly lower than that in L group In period III and IV（P≤0.01）.The PD index of EL group was significantly lower than that the L group in period I（April）（P<0.05）,while significantly higher than that of the control group in period III（July）（P<0.01）.PCo A and clustering analysis showed that samples of the EL group were closer than that of the L group form period III and IV,the samples overlapped and clustered into one class.Compared with L group,the content of nitrite nitrogen of EL group decreased significantly in period III（P<0.05）.Studies have shown that the addition of EM could improve the water quality of aquaculture water,effectively inhibits cyanobacteria and mycobacteria,and improve the stability of micro-ecosystem of aquaculture water.2.Effect of effective microorganisms（EM）on aquatic bacterial community structure in polyculture mode of Eriocheir sinensis and Micropterus salmoides The 16S r RNA high-throughput sequencing results showed that the dominant phyla were Proteobacteria,Actinobacteriota,Firmicutes and Cyanobacteria during the whole experiment period.Meanwhile,the relative abundance of Cyanobacteria in the control group was significantly higher than that the experimental group in period III and IV（P<0.05）.In compare with the control group,Limnohabitans（20.34%）was the most dominant in genus level in period I,whereas Exiguobacterium occupied the most abundant in other three periods（56.33%,38.11%,17.88%）.However,Rhodoferax（10.37%）,Exiguobacterium（47.67%）,and Mycobacterium（36.01%,42.27%）were the most abundant in each periods of the control group.The Sobs and PD indexes of the experiment group was significantly higher than that of the control group in periodⅢandⅣ（P<0.05）.Compared with the control group,the total nitrogen（TN）of the experiment group was significantly decreased during the whole monitoring periods（P<0.05）,moreover,the content of ammonia nitrogen decreased significantly in periodⅡ,ⅢandⅣ（P<0.05）.Correlation analysis of environmental factors showed that total nitrogen had the greatest impact on the bacterial community,the Exiguobacterium as the dominant probiotics in the experimental group were positively correlated with TP and negatively correlated with TN,NH₄⁺-N,NO₃^--N,NO₂^--N.Studies have shown that the addition of EM could improve the water quality of aquaculture water,effectively inhibited Cyanobacteria,significantly optimized the bacterial structure,had significant in-situ water remediation function.3.Effects of effective microorganisms supplementation and polyculture mode on growth,antioxidant and immune capacity of Micropterus salmoides The body weight and weight gain rate of Micropterus salmoides were improved by sprinkling EM regularly in Micropterus salmoides culture pond,but the effect was not significant（P>0.05）.The results of liver antioxidant and immune indexes showed that SOD,CAT and GSH-Px in liver of Micropterus salmoides in EL group were significantly higher than those in L group（P<0.05）.The ACP activity of liver in L group was significantly higher than that in EL group at the early stage of culture,and that in EL group was higher than that in L group at the late stage,but the difference was not significant（P>0.05）.AKP in EL group was always significantly higher than that in L group（P<0.05）.The end body weight and weight gain rate in ML group were significantly higher than those in EL group.The results of serum physiological and biochemical indexes showed that serum LDH and AST in ML group were significantly higher than those in EL group,while ALP in ML group was significantly lower than that in EL group（P<0.05）.The results of liver antioxidant and immune indexes showed that SOD activity in ML group was significantly higher than that in EL group,while GSH-Px in EL group was significantly higher than that in ML group（P<0.05）.CAT of ML group was significantly higher than that of EL group at the later stage（P>0.05）.The activity of ACP in liver of ML group was significantly higher than that of EL group in the early stage,but there was no significant difference in the late stage.The activity of AKP in LIVER of ML group was always significantly higher than that of EL group（P<0.05）.The results showed that EM supplementation could significantly improve the immune and antioxidant capacities of Micropterus salmoides,and the immune and antioxidant capacities of Micropterus salmoides were further improved under mixed culture mode.4.Effects of effective microorganisms supplementation and polyculture mode on muscle quality of Micropterus salmoides The results of muscle basic composition and free amino acid determination showed that there were no significant differences between EL group and L group（P>0.05）.The hydrolyzed amino acid content of arginine in dorsal muscle of largemouth bass in L group was significantly higher than that in EL group（P<0.05）,but there were no significant differences in other amino acids.Saturated fatty acids lauric acid and myristic acid in EL group were significantly lower than those in L group,monounsaturated fatty acid erucic acid was significantly lower than that in control group,and polyunsaturated fatty acid arachidonic acid was significantly higher than that in control group（P<0.05）;Nucleotide determination showed no significant difference between the two culture groups（P>0.05）.There was no significant difference in the contents of hydrolyzed amino acids in back muscle between ML group and EL group,but the content of aspartic acid,glutamic acid,methionine,isoleucine and valine in free amino acids in EL group was significantly higher than that in ML group（P<0.05）.The content of linolenic acid and eicosapentaenoic acid in muscle polyunsaturated fatty acids in ML group was significantly higher than that in EL group（P<0.05）,while the content of saturated fatty acids in EL group was significantly higher than that in ML group.The content of guanylic acid in ML group was significantly higher than that in EL group.The results showed that EM supplementation had positive effect on improving muscle quality of largemouth bass.Micropterus salmoides in mixed culture mode has larger size,better antioxidant and immune capacity,and better muscle quality,but there is a certain loss of flavor quality.