In this study, we hypothesized that sympatrically grown farmed fish, i.e. fish which experience similar environmental conditions and nutritionally similar diets, would have more convergent gut microbiota. Using a “common garden” approach, we identified the core microbiota and bacterial community structure differences between five fish species farmed in the same aquaculture site on the west coast of the Aegean Sea, Greece. The investigated individuals were at similar developmental stages and reared in adjacent (< 50 m) aquaculture cages; each cage had 15 kg fish m⁻³. The diets were nutritionally similar to support optimal growth for each fish species. DNA from the midgut of 3–6 individuals per fish species was extracted and sequenced for the V3–V4 region of the bacterial 16S rRNA. Only 3.9% of the total 181 operational taxonomic units (OTUs) were shared among all fish. Between 5 and 74 OTUs were unique to each fish species. Each of the investigated fish species had a distinct profile of dominant OTUs, i.e. cumulative relative abundance of ≥ 80%. Co-occurrence network analysis for each fish species showed that all networks were strongly dominated by positive correlations between the abundances of their OTUs. However, each fish species had different network characteristics suggesting the differential significance of the OTUs in each of the five fish species midgut. The results of the present study may provide evidence that adult fish farmed in the Mediterranean Sea have a rather divergent and species-specific gut microbiota profile, which are shaped independently of the similar environmental conditions under which they grow.

在这项研究中，我们假设同伴生长的养殖鱼类（即经历相似环境条件和营养相似饮食的鱼类）具有更多的会聚肠道菌群。使用“公共花园”方法，我们确定了希腊爱琴海西海岸同一水产养殖场养殖的五种鱼类之间的核心微生物群和细菌群落结构差异。被调查的个体处于相似的发育阶段，并在相邻的（<50 m）水产养殖网箱中饲养；每个网箱有15千克鱼m ^-3。饮食在营养上相似，以支持每种鱼类的最佳生长。从每种鱼类的3–6个个体的中肠提取DNA并对其16S rRNA细菌的V3–V4区域进行测序。在所有鱼类中，共有181个操作生物分类单位（OTU）中只有3.9％被共享。每个鱼类独特的OTU介于5到74之间。每个被调查的鱼类具有显着的主要OTU轮廓，即累积相对丰度≥80％。对每种鱼类的共现网络分析表明，所有网络都以其OTU的丰度之间的正相关性为主导。但是，每种鱼类都有不同的网络特征，这表明五种鱼类中肠中的OTU的重要性不同。