长江宜宾-江津段漂流性鱼卵纵向分布特征及与环境因子关系

Longitudinal Distribution of Drifting Fish Eggs from Yibin to Jiangjin in the Upper Yangtze River and the Relationship with Environmental Factors

通过2023年4-7月对长江上游宜宾、合江和江津断面鱼类早期资源的逐日监测,了解漂流性鱼卵种类组成、鱼卵径流量、产卵高峰期及产卵场的纵向分布特征,分析逐日产卵径流量变动与水文、水温条件的关系,明晰不同断面鱼卵径流量峰值出现的流量区间,辨识影响鱼卵径流量变动的关键环境要素。结果表明:共采集到漂流性鱼卵24种,包括长江上游特有鱼类鱼卵8种,其中红唇薄鳅(Leptobotia rubrilabris)、长薄鳅(L.elongata)、长鳍吻鮈(Rhinogobio ventralis)为国家二级保护动物;流经宜宾、合江和江津断面的漂流性鱼卵总径流量分别为729.45×10^(4)、17301.92×10^(4)和76027.44×10^(4)粒,鱼卵总径流量从上游到下游呈明显增加的特征;3个断面鱼卵径流量的高峰期出现在5月下旬以后,其中宜宾断面最早,江津断面次之,合江断面最晚;金沙江一期工程蓄水后,保护区干流江段产卵场的纵向分布特征发生了明显改变,主要产卵场位置下移;流量上涨量、水位上涨量和流量日上涨率是影响3个断面鱼卵径流量变动的最重要因素。研究结果可为长江上游保护区干流鱼类早期资源保护、生态调度等提供科学依据。

Early-stage fish resources are an important indicator that reflect variations in fish community dynamics.Fish species that spawn drifting eggs are one of the main ecological fish groups in the upper Yangtze River and an important component of fish species diversity.Therefore,variation of early-stage resources of these species effectively reflect the health of the aquatic ecosystem.In this study,we carried out daily monitoring of early-stage fish resources in the Yibin,Hejiang and Jiangjin sections of the upper Yangtze River from April to July 2023.Based on the monitoring results,we analyzed species composition of eggs,egg runoff,peak spawning period and the longitudinal distribution of spawning grounds for species that release drifting eggs.The relationship between daily variation of fish egg runoff and environmental variables(hydrologic conditions and water temperature)was then analyzed.Finally,the flow interval where peak egg runoff appeared in the different sections,and the key environmental factors affecting fish egg runoff were identified.A total of 24 fish species that spawn drifting eggs were collected,including 8 species endemic to the upper Yangtze River,among which are three species(Leptobotia rubrilabris,L.elongata,and Rhinogobio ventralis)that are national second-class protected animals.The total runoff of drifting eggs flowing through the Yibin,Hejiang and Jiangjin sections were,respectively,729.45×10^(4),17301.92×10^(4) and 76027.44×10^(4),and the total runoff of fish eggs clearly increased from upstream to downstream.The peak of fish egg runoff in all three sections appeared after the end of May,with the Yibin section being the earliest(May 24-29,June 2),followed by the Jiangjin section(June 3-4,July 5)and the Hejiang section(July 6,July 13-15).After the first phase of the project,when Jinsha River was impounded,the longitudinal distribution of spawning grounds in the mainstem of the upper Yangtze River changed markedly,and the main spawning grounds moved downstream.The increases in discharge,water level and daily discharge rate were the most important factors affecting the variation of fish egg runoff in the three sections.These results provide a scientific basis for implementing early fish resource protection measures,especially the regulation of ecological flow in the upper reaches of the upper Yangtze River.