Host-associated microbiota play important roles in the nutrition, immune system, and health of fish. However, the composition, diversity, and function of microbiota associated with certain niches in fish bodies and fish habitats remain to be elucidated. In the present study, 16S sequencing was carried out to compare microbial communities found in the gills and guts in two filter-feeding fish (Hypophthalmichthys molitrix and Hypophthalmichthys nobilis) and to determine the influence of sediment and water on fish microbiota in an unfed aquaculture system. Results revealed significant variations in the water, sediment, gill, and gut microbial communities of the two filter-feeding fish in terms of composition, core taxa, diversity, and predictive function. Microbial diversity was significantly higher in the habitat samples (water and sediment) than in the fish host samples (gill and gut) and was significantly higher in the gills than in the gut. Both body niche (i.e., gill vs gut) and host species significantly impacted the fish-associated microbiota, but permutational multivariate analysis of variance (PERMANOVA) and cluster analysis of core taxa indicated that the effect of body niche outweighed that of the host species in influencing the microbial community. Host microbial communities were more similar to the water microbiota than the sediment microbiota. Source tracking analysis further confirmed that water had a greater contribution than sediment to the fish microbiota, consistent with their upper water-layer habitats. The gill and gut possessed unique core microbiota and predictive functions in comparison to the surrounding environment. These findings should improve our understanding of the composition, diversity, and function of aquatic host microbiota and their associations with habitat.

寄主相关微生物群在鱼类的营养，免疫系统和健康中起着重要作用。然而，与鱼体和鱼类生境中某些生态位有关的微生物群的组成，多样性和功能仍有待阐明。在本研究中，我们进行了16S测序，以比较两种滤食性鱼类（Hypophthalmichthys molitrix和Hypophthalmichthys nobilis）在g和内脏中发现的微生物群落。），并确定沉积物和水对未饲喂水产养殖系统中鱼类微生物的影响。结果表明，两种滤食鱼的水，沉积物，g和肠道微生物群落在组成，核心类群，多样性和预测功能方面均存在显着差异。栖息地样品（水和沉积物）中的微生物多样性显着高于鱼类寄主样品（腮和肠）中的微生物多样性，而ill中的微生物多样性显着高于肠道中的微生物多样性。体位（即g和肠道）和寄主物种均显着影响与鱼类相关的微生物群，但变异多变量方差分析（PERMANOVA）和核心类群的聚类分析表明，体位的影响超过寄主物种。影响微生物群落。宿主微生物群落比沉积物微生物群更类似于水微生物群。来源跟踪分析进一步证实，与鱼类沉积物相比，水对鱼类微生物的贡献更大，这与其上层水生境一致。与周围环境相比，和肠道具有独特的核心微生物群和预测功能。这些发现应增进我们对水生宿主微生物群的组成，多样性和功能及其与生境的联系的了解。与周围环境相比，和肠道具有独特的核心微生物群和预测功能。这些发现应增进我们对水生宿主微生物群的组成，多样性和功能及其与生境的联系的了解。与周围环境相比，和肠道具有独特的核心微生物群和预测功能。这些发现应增进我们对水生宿主微生物群的组成，多样性和功能及其与生境的联系的了解。