The Caspian Sea (CS) is a unique ecosystem known for its several fish species, especially sturgeons. To exhaustively manage the fish stocks of this ecosystem, detailed knowledge of species composition, abundance, distribution, and the habitat traits of the living organisms is necessary. This study analyzed the diversity, spatial, and seasonal distribution of commercial demersal fish species, and examined the relationships between community structure and environmental variability in Iranian shelf waters of the CS. For this purpose, seasonally fish sampling took place between 2009 and 2011 with a bottom trawl. Among 11 fish species captured, Chelon spp., Rutilus kutum, and Vimba vimba showed the highest abundances (i.e. 88.49%, 10.67%, and 0.69%, respectively). Univariate and multivariate analyses showed differences in commercial fish assemblages (abundance and species richness) according to seasons and regions. Distance-based Linear Model (DisTLM) showed that eight environmental variables display significant linear relationships with the fauna resemblance matrix (p < .05). Based on AIC criteria, the combination of silt&clay, TOM, longitude, depth, bottom, and surface temperature used to build the parsimonious DisTLM model explain 67.03% of the total variability. The results revealed a biogeographical and temporal gradient from the west to the east and summer to winter, in terms of commercial demersal fish assemblages and species diversity, as a consequence of different geomorphological, bottom substratum conditions and benthic communities.

中文翻译：

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里海陆架水域商业底层鱼类的空间分布和多样性

里海 (CS) 是一个独特的生态系统，以其多种鱼类，尤其是鲟鱼而闻名。为了彻底管理该生态系统的鱼类种群，需要详细了解物种组成、丰度、分布和生物体的栖息地特征。本研究分析了商业底层鱼类物种的多样性、空间和季节性分布，并研究了伊朗大陆架水域中群落结构与环境变异之间的关系。为此，在 2009 年至 2011 年期间使用底拖网进行了季节性鱼类取样。在捕获的 11 种鱼类中，Chelon spp.、Rutilus kutum和Vimba vimba的丰度最高（即. 88.49%、10.67% 和 0.69%）。单变量和多变量分析显示商业鱼类组合（丰富度和物种丰富度）根据季节和地区存在差异。基于距离的线性模型 (DisTLM) 显示八个环境变量与动物群相似性矩阵 ( p < .05）。根据 AIC 标准，用于构建简约 DisTLM 模型的粉砂和粘土、TOM、经度、深度、底部和地表温度的组合解释了总变异性的 67.03%。结果表明，在商业底层鱼类组合和物种多样性方面，由于不同的地貌、底层基质条件和底栖群落，从西到东、从夏季到冬季存在生物地理和时间梯度。