禁捕初期长江下游鱼类群落现状分析及禁渔效果初步评估

Status analysis of fish community in the lower reaches of the Yangtze River at the beginning of 10-year fishing ban and assessment of fishing ban effect

为了解禁捕初期长江下游鱼类群落结构特征,实验于2021年春季、夏季、秋季和冬季对长江下游鱼类群落进行4次调查。结果显示,实验共采集鉴定鱼类84种,分属10目18科63属,其中47.62%为鲤科鱼类。以物种数和多样性指数分析群落多样性特征,结果表明长江下游鱼类多样性水平较高,但鱼类种类较历史记录偏少。单因素方差结果显示,鱼类种类数、种群数量和重量空间差异显著,季节差异不明显。群落优势种为光泽黄颡鱼、鳊、鲢、短颌鲚、贝氏䱗等9种。4种摄食功能群中,肉食性(47.62%)和杂食性(40.47%)鱼类物种比例较高;洄游习性方面,淡水定居性鱼类占绝对优势(76.19%);3种栖息水层类型中,底层鱼类物种数比例较高(46.43%)。大型经济鱼类占总量比例低,但个体相对较大,因而相对重要性指数(IRI)更高。长江下游鱼类多样性指数为3.28,水域鱼类多样性水平较高。长江下游鱼类个体小型化、低龄化现象依然存在,长江十年禁渔实施后,禁渔效果初步显现,鱼类物种数、多样性指数和单位捕捞努力量渔获量均有所增加。建议进一步加强禁捕期科研监测,加大监管力度,保障长江下游鱼类资源得以有效恢复,巩固禁捕成效。本研究可掌握禁捕初期长江下游鱼类群落基本特征及变动趋势,为长江下游禁渔效果评估和长江水生生物完整性指数评价提供支撑。

Water course in the lower reaches of the Yangtze River is bent,and flow pattern is tangled,which leads to diverse habitat,and makes it a good breeding,feeding place and important migration channel for fish.In order to study the fish community structure during initial period of 10-year fishing ban,fish was collected seasonally from April to December 2021,in the lower reaches of the Yangtze River.A total of 84 fish species from 63 genera,18families and 10 orders were collected during the investigation,with dominance by Cyprinids(47.62% of total species).Results of the species numbers and diversity indices showed that fish diversity was high in the lower reaches of the Yangtze River,while species are less than historical records.One-way ANOVA indicated that significant spatial differences were found for fish species,number and biomass,while no obvious differences were observed among seasons.Pelteobaggrus nitidus,Parabramis pekinensis,Hypophthalmichthys molitrix,Coilia brachygnathus,Hemiculter bleekeri and other 4 species were the dominant species.Piscivorous(47.62%)and omnivorous(40.47%)fishes prevailed in species number among the 4 feeding functional groups,sedentary fishes(76.19%)predominated among the 3 ecological groups,and demersal fishes(46.43%)predominated among the 3 habitat types.The number of large commercial fishes account for a small part of the fish community,but the index of relative importance is high due to the comparatively large individuals.The Shannon-Weiner index in the lower reaches of the Yangtze River is 3.28,which indicate the fish is relatively diversified.In the present study,the richness index was also high,while community evenness was stable.Overall,the fish continue to become smaller and younger,the fishery resources declined clearly,fish species,diversity index and catch per unit effort increased during initial period of 10-year fishing ban,and effect of the prohibition gradually appeared.In order to consolidate the effect of 10-year fishing ban,promote fish resources recovery,and optimize fish community structure,further scientific monitoring and higher strength patrol were recommended in the Yangtze River.Our study can obtain the basic characteristics of fish communities during initial period of 10-year fishing ban,and can also provide reference for fishing ban effect evaluation and aquatic organisms integrity index assessment.