雅砻江支流安宁河鱼类群落组成及资源现状

为了解安宁河鱼类资源现状,于2013年3月至2014年12月对安宁河及其支流18个采样点进行了5次调查,共计采集鱼类3 113尾,隶属4目、10科、35属、52种,其中长江上游特有鱼类13种;鱼类区系包括中国平原、南方平原、南方山地、中亚山地、北方平原和晚第三纪早期6个区系复合体;其中,中亚山地区系复合体占优(40.4%)。安宁河不同河段Jaccard's相似性指数在0.12~0.47,鱼类群落相似性总体较低。根据IRI(100为优势种)指数计算结果,麦穗鱼(Pseudorasbora parva)、齐口裂腹鱼(Schizothorax prenanti)、红尾副鳅(Paracobitis variegatus)、西昌高原鳅(Triplophysa xichangensis)、斯氏高原鳅(Triplophysa stoliczkae)、东方高原鳅(Triplophysa orientalis)、鲇(Silurus asotus)和白缘鱼央(Liobagrus marginatus)8种鱼类为安宁河优势种。根据个体生物学测量,安宁河主要渔获对象规格较小,齐口裂腹鱼均重285.8 g/尾,红尾副鳅均重7.2 g/尾,鲫(Carassius auratus)均重78.3 g/尾,鲤(Cyprinus carpio)均重361.1 g/尾,鲇均重93.7 g/尾,表明可能存在过度捕捞现象。多样性分析显示,Margalef丰富度指数(R)在1.95~4.47,Shannon-Wiener多样性指数(H)在1.75~2.33,Pielou均匀度指数(E)在0.67~0.73。安宁河鱼类多样性相比同区域其它河流偏低,可能与安宁河鱼类群落受到各种干扰、生境异质性降低、鱼类群落已发生演替有关。对比历史资料,鱼类种类数从82种下降至52种,在不同区域的各分类阶元均有所减少,且有自上而下加重的趋势。水电开发、河道采砂以及资源不合理利用等是影响安宁河鱼类资源的主要因素。基于研究结果,建议尽快加强安宁河鱼类资源保护。

Community Composition and Status of Fish Resources in Anning River

Anning River is one of the largest tributaries of the Yalong River. In recent years, the fish community structure in Anning River has been altered by cascade hydropower development in the Yalong River basin. The aim of this study was to investigate the current situation and trend of fish resources in Anning River and advise protection strategies by analyzing the factors affecting the fish resources. The study will provide basic data and reference for decision making for fishery conservation in the Anning River basin. Field investigation of fishery resources was carried out at 18 sampling sites at 5 times along the main stem of Anning River and its tributaries from March 2013 to December 2014. Fish were captured by electroshocking, gill nets and fish cages. Species identification and taxonomic classification were completed using the existing literature and length and mass of all specimens were measured. A total of 3113 individuals from 52 species were collected, belonging to 35 genera, 10 families and 4 orders. During the investigation, 13 species endemic to the upper Yangtze River were observed and the fish collected in the Anning River were divided into 6 different faunas, dominated by those endemic to central Asian mountains (40.4% of the total species). The Jaccard similarity index, calculated for communities in different reaches of Anning River ranged from 0.12 to 0.47, indicating a low similarity. Based on IRI (Index of Relative Importance) and fish measurement results, 8 dominant species were recorded, including Pseudorasbora parva, Schizothorax prenanti, Paracobitis variegatus, Triplophysa xichangensis, Triplophysa stoliczkae, Triplophysa orientalis, Silurus asotus, and Liobagrus marginatus. However, the size of the primary fish catches was small and average weights of the five dominant species were 285.8 g (Schizothorax prenanti), 7.2 g (Paracobitis variegates), 78.3 g (Carassius auratus), 361.1 g (Cyprinus carpio) and 93.7 g (Silurus asotus). These small sizes indicate overfishing. The Shannon-Wiener diversity index (H), Margalef richness index (R) and Pielou evenness index (E) of the fish community in Anning River ranges were 1.75-2.33, 1.95-4.47 and 0.67-0.73, respectively, much lower than in most of the rivers of the upper Yangtze River. This is symptomatic of human disturbances that decrease habitat heterogeneity and it has led to succession of the fish community in Anning River. Compared with the historical data, the number of fish species decreased from 82 to 52. The fish species richness in all taxonomic categories decreased in different reaches and tended to decrease more from the upper to lower reaches of the river. The fish resource in Anning is severely threatened by intensive human activities, including hydroelectric development, sand excavation and overfishing. We strongly suggest that protection fish resources in Anning River should be carried out as soon as possible.