Understanding biodiversity and community composition is a prerequisite to sustainable exploitation and conservation of fisheries. We assessed the spatial and seasonal patterns of fish community composition and biodiversity in seasonal no‐take riverine sanctuaries in Bangladesh, which aim to conserve the anadromous hilsa shad (Tenualosa spp. and Hilsa keele). Fish samples were collected during monsoon, as well as pre‐ and postmonsoon, from five sites within two sanctuaries and one site in an open fishing area. Although total abundance was similar along the rivers, species richness was significantly higher at the open fishing site due to its connectivity to nearby habitats. The diversity apparently decreased in a downstream direction. Fish communities at two upstream sites were separated from other sites in multivariate space largely due to higher abundance of hilsa at downstream sites and presence of floodplain‐oriented species at the two upstream sites. Short body length and high trophic level at all sites indicated that fish communities were overexploited. Our results also indicated that riverine hilsa sanctuaries in Bangladesh are rich in fish species diversity and support several threatened species designated by the International Union for Conservation of Nature (IUCN). Our study also suggested that since hilsa abundance shapes community patterns, it can therefore impact riverine ecosystem functioning in the sanctuary areas. The findings of this study can serve as an important baseline for future biodiversity assessment, conservation and impact assessment of conservation in rivers, and therefore help to establish multispecies ecosystem‐based management of riverine fisheries around the world.

中文翻译：

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孟加拉国河流鱼类保护区鱼类群落组成和生物多样性的模式：对鲥鱼保护的影响

了解生物多样性和群落组成是渔业可持续开发和保护的先决条件。我们评估了孟加拉国季节性禁捕河流保护区鱼类群落组成和生物多样性的空间和季节性模式，旨在保护溯河鲥鱼（Tenualosa spp. 和 Hilsa keele）。在季风期间以及季风前后，从两个保护区内的五个地点和一个开放捕鱼区的一个地点收集了鱼类样本。尽管沿河的总丰度相似，但由于开放捕捞点与附近栖息地的连通性，物种丰富度明显更高。多样性在下游方向明显减少。两个上游站点的鱼类群落在多元空间中与其他站点分离，这主要是由于下游站点的 hilsa 丰度较高，并且两个上游站点存在面向洪泛区的物种。所有地点的短体长和高营养水平表明鱼类群落被过度开发。我们的研究结果还表明，孟加拉国的河流 hilsa 保护区拥有丰富的鱼类物种多样性，并支持国际自然保护联盟 (IUCN) 指定的几种受威胁物种。我们的研究还表明，由于 hilsa 丰度塑造了群落模式，因此它可以影响保护区区域的河流生态系统功能。这项研究的结果可以作为未来生物多样性评估的重要基线，