长江安庆新洲江段仔稚鱼的群聚特征

安庆新洲江段是长江下游典型的干流-沙洲生境，为掌握该水域仔稚鱼群聚特征，于2018年4月15日—8月4日开展了逐日调查。调查期间，共采集鉴定仔稚鱼121246尾，隶属于6目8科34种，贝氏䱗（）为第一优势种。新洲南汊、北汊分别采集仔稚鱼79338尾和41908尾，数量占比依次为65.44%和占34.56%。所有渔获物中，产漂流性卵鱼类物种数最多（16种，47.06%），产浮性卵鱼类数量最多（92623尾，76.39%）。就时间特征而言，南汊、北汊仔稚鱼丰度日变化趋势基本一致，表现出与水位上涨高度关联，共监测到三次高峰，其中7月13日达到峰值（2001.28 ind/100 m³）；就空间特征而言，近岸采样点丰度高于河道中泓采样点，南汊丰度总体高于北汊。冗余分析结果显示，与新洲江段仔稚鱼丰度相关性较强的环境因子为水位、浊度、水温和透明度，其中水位为主要的正相关因子。空间尺度的聚类分析将新洲江段6个采样点分为3个群组，表明新洲江段不同采样点仔稚鱼群聚结构差异显著（=0.017）。研究表明，安庆新洲江段仔稚鱼补充量显著大于上游输入量，新洲对该江段仔稚鱼群聚特征具有显著影响，总体表现为南汊的鱼类繁殖条件显著优于北汊。研究结果补充了安庆新洲江段鱼类早期资源的基础数据，为长江下游渔业资源评估与保护提供了依据。

Assemblage of larvae and juvenile fish in Anqing Xinzhou section of the Yangtze River

Xinzhou section is a typical stream-sandbank habitat in the lower reaches of the Yangtze river. In order to understand the larvae and juvenile fish assemblage feature in this section, Structure, dominant species, abundance and spatial-temporal distribution were investigated, from April 15 to August 4, 2018, and the relationships with environmental factors were probed at the same time. 121246 larvae and juvenile fish were identified, belonging to 6 orders, 8 families and 34 species. 79338 larvae and juvenile fish were captured in the south branch, accounting for 65.44% of the whole species; and 41908 in the north branch, accounting for 34.56%. Among the spawning types, fish species with pelagic eggs (16) were dominant; whereas, fish with floatability eggs taken the largest number, which were 92623 individuals. was the first dominant species and other dominant species are Rhinogobius giurinus. The diurnal variation trend of abundance in north and south branch were consistent. The larval and juvenile fish abundance reached its peak level (2001.28 ind/100 m³) on July 13, which showed a high correlation with water level. The abundance of inshore sampling points was higher than that of mid-channel, and the abundance of south branch was higher than that of north branch. Redundancy analysis found that water level, water temperature, turbidity and transparency are the main environmental factors affecting the assemblage structure of larval and juvenile fish. Water level is the main positive correlation factor. The cluster analysis divided the 6 sampling points into 3 groups, showing significant differences in assemblage structure of larval and juvenile fish (=0.017). The results showed that there was a significant influence on the distribution of larvae and juvenile fish in Xinzhou section, and the breeding conditions of fish in the south branch were better. The results provided the scientific data of the early fish resource in Xinzhou section and the protection strategy of fish resource in the lower reaches of the Yangtze River.