Abstract

An unfavorable hydrological regime has contributed in recent years to negative changes in the species and age structure of the ichthyofauna in the northern part of the Agrakhan Bay of the Caspian Sea. The article presents the data on the species composition, age categories and morphometric indicators of semi-anadromous and freshwater fish species in detail based on the results of studies in 2019–2021. A comparative analysis of the obtained results with the data of previous years was carried out; negative dynamics of changes in the studied indicators under modern conditions were established. There has been a reduction in the species composition of semi-anadromous fish from 14 to 9 species, the commercially valuable kutum Rutilus kutum (Kamensky, 1901), catfish Silurus glanis (Linnaeus, 1758), vimba Vimba vimba (Linnaeus, 1758), tench Tinca tinca (Linnaeus, 1758) and asp Aspius aspius (Linnaeus, 1758) have disappeared, the share of the remaining surviving species has significantly decreased. The average age has increased, the proportion of fish of older age categories has grown, and, accordingly, the number of younger groups of fish has decreased, which indicates a decrease in growth potential. At the same time, freshwater low-value fish species such as crucian carp Carassius gibelio (Bloch, 1782), rudd Scardinius erythrophthalmus (Linnaeus, 1758), white bream Blicca bjoerkna (Linnaeus, 1758), and others have growth trends in terms of age and morphometric parameters.

中文翻译：

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阿格拉罕湾北部半溯河产卵和非溯河产卵鱼类现状的比较评估

摘要

近年来，不利的水文状况导致里海阿格拉罕湾北部鱼类动物群的物种和年龄结构发生负面变化。文章根据2019-2021年的研究结果，详细介绍了半溯河产卵鱼类和淡水鱼类的物种组成、年龄类别和形态指标数据。将所得结果与往年数据进行了对比分析；建立了现代条件下研究指标变化的负面动态。半溯河产卵鱼类的种类组成从 14 种减少到 9 种，其中有商业价值的 kutum Rutilus kutum (Kamensky, 1901)、鲶鱼Silurus glanis(Linnaeus, 1758)、vimba vimba vimba (Linnaeus, 1758)、丁鳐Tincatinca (Linnaeus, 1758) 和 aspius aspius (Linnaeus, 1758) 已经消失，剩余幸存物种的比例已显着减少。平均年龄增加，高年龄组鱼类的比例增加，相应地，年轻组鱼的数量减少，这表明生长潜力下降。同时，淡水低价值鱼类如鲫鱼Carassius gibelio（Bloch，1782）、红眼鲫鱼（Linnaeus，1758）、白鲷Blicca bjoerkna（Linnaeus，1758）等人在年龄和形态参数方面有增长趋势。