Effects Of Three Culture Modes On Intestinal Microbial Communities And Muscle Quality Of Largemouth Bas

American Black Bass(Micropterus salmoides)is an important economic fish for freshwater aquaculture in China,because of its tender meat,rich in nutrition and other advantages favored by the people,contradiction between decreasing fishery resources and increasing market demand,Therefore,improving farming efficiency and enhancing the quality of American Black Bass are the main issues for Breeder。At present,domestic fish farming mainly includes models intensive culture pond,cultured in circulating flume and net cage culture,environmental variability in different models can lead to differences in organisms,and geographic location,water quality and culture conditions can all affect aquatic growth metabolism,nutrient composition and intestinal status。In this study,the analysis was carried out under three common farming modes,intensive culture pond,cultured in circulating flume and Higher-place pond,using American Black Bass as the subject.First,the biological indicators of American Black Bass in the three models were measured to compare the differences in morphology and quality,and to analyze the effect of the environment on the morphology of American Black Bass;Sequencing the gut microbes of American Black Bass in three models to analyze the differences in gut microbes of American Black Bass in different environments;Determination of nutrient composition and flavor substances of American Black Bass muscles in three modes,and comparison of the nutritional quality of American Black Bass in different modes 。The study results are as follows:The length traits,weight traits and volume traits of American Black Bass were measured in each of the three culture modes,and the differences between the morphological evaluation indices and the principal component analysis of the nature characteristics were compared,and it was learned that there were significant differences in the morphology of American Black Bass under the three culture modes.Among them,the morphological dimension of American Black Bass in the high pond culture mode was smaller and the growth and development was relatively slow,which might be due to the stress response caused by the high culture density and triggered physiological stress,or the deterioration of water quality caused by high density culture affected fish development,and the best morphological phenotype of American Black Bass in the flow tank mode.The gut contents of American Black Bass from three different culture modes were collected for DNA extraction and high-throughput sequencing,and 27,5520,29,9607 and23,6016 sequences were obtained,respectively.Based on the species annotation results,all OTUs belonged to 31 phyla,74 orders,173 families,218 families and 353 genera,demonstrating that American Black Bass gut microorganisms are rich in species diversity.The gut microflora of American Black Bass in different culture modes were proved to be significantly different by phylum level,while Proteobacteria,Fusobacteria and Firmicutes were the dominant genera of American Black Bass.Alpha diversity analysis and Beta diversity analysis proved that there were significant differences in the composition of gut microorganisms of American Black Bass in the three culture modes.The general nutrients,amino acids,fatty acids and flavor active substances of American Black Bass muscles were determined in three different groups of culture modes,respectively,and the experiments showed that the ash and crude fat contents were higher in the pond culture mode and the protein content of American Black Bass was higher in the flow-through tank culture mode;The EAA/TAA and EAA/NEAA values of all three American Black Bass groups were greater than the reference protein amounts proposed by FAO/WHO,and the TAA,NEAA and DAA of American Black Bass in the flow-through tank culture mode were significantly higher than those of the pond culture group and the raised pond group;A total of 15 fatty acids were measured by gas chromatography.Among the three groups of data,SFA,MUFA and PUFA were significantly different,and the content of EPA + DHA in the flow-through tank culture mode was significantly higher than that in pond culture and high pond culture;A total of 69 flavor active substances were identified by SPME-GC-MS,among which volatile components mainly included aldehydes,ketones,alcohols,alkanes and olefins,etc.The high level pool was more flavorful compared with other models.