Regulatory effects of polyculture with Pelteobagrus fulvidraco on the nutritional quality， intestinal microbiota， and aquaculture micro-ecological environment of Micropterus salmoides

Objective This study aimed to discuss the effects of polyculture with Pelteobagrus fulvidraco on the growth performance， nutritional quality， intestinal microbiota and aquaculture micro-ecological environment of Micropterus salmoides， so as to identify the appropriate polyculture ratio， thereby providing a scientific basis for the ecofriendly and healthy culture of Micropterus salmoides.Method Experimental groups were Micropterus salmoides monoculture group （Group C）， low-density polyculture group （Micropterus salmoides∶Pelteobagrus fulvidraco=4∶1， Group L）， middle-density polyculture group （Micropterus salmoides∶Pelteobagrus fulvidraco=2∶1， Group M）， and high-density polyculture group （Micropterus salmoides：Pelteobagrus fulvidraco=1∶1， Group H）. After 60 days of feeding， the growth performance， muscle nutritional quality， intestinal microbiota of Micropterus salmoides， and characteristics of microbial community in aquaculture water were determined.Result In Group M， the specific growth rate （1.69 %/d） and the condition factor （1.52） of Micropterus salmoides were the highest， but the feed coefficient （1.08） was the lowest. The crude protein content in Micropterus salmoides muscle of Groups M and Group H was significantly higher than that of the Group C （P<0.05， the same below）. The contents of essential amino acids and umami amino acids in Micropterus salmoides muscle in the Group M were significantly higher than those in the Group C. The muscle hardness and tackiness of Micropterus salmoides in the Group M were significantly higher than those in the Group C， but the contents of earthy odor substances （geosmin and 2-methylisoborneol） was significantly lower than that in the Group C. Polyculture with Pelteobagrus fulvidrac had an obvious impact on the intestinal microbial community structure of Micropterus salmoides. Compared with Micropterus salmoides in the Group C， the relative abundances of Bacillota and Pseudomonadota in the intestine of Micropterus salmoides in the Group M were significantly increased， whereas the relative abundance of Actinomycetota was significantly decreased. The relative abundance of Sphingomonas increased significantly as the Pelteobagrus fulvidraco density increased， and it had a significantly positive correlation with the muscle crude protein content. Moreover， polyculture with Pelteobagrus fulvidraco led to marked changes in the structure of microbial community in aquaculture water for Micropterus salmoides： The relative abundances of Massilia and Exiguobacterium in the Group M were significantly higher than those in the Group C； the relative abundance of Exiguobacterium had a highly significant positive correlation with Chlorophyta density in the water bodies （P<0.01） and a significant correlation with the relative abundance of Sphingomonas in the intestinal microbiota of Micropterus salmoides.Conclusion The polyculture of Micropterus salmoides and Pelteobagrus fulvidraco with ratio of 2∶1 could reshape the aquaculture ecology， therefore， it can significantly improve the growth performance and muscle nutritional quality， and optimize the structure of intestinal microbiota and aquatic microbial community for Micropterus salmoides， thus achieving a synergistic improvement in growth， quality and environment， making it an ideal ecological aquaculture model.