长江湖口段春夏季仔稚鱼群落结构研究

湖口江段连通长江与鄱阳湖, 是诸多鱼类的洄游通道, 在长江鱼类的繁衍生息中发挥重要功能。研究于2016年5月—8月在长江中下游鱼类繁殖期内对湖口江段系统开展鱼类仔稚鱼资源的调查, 研究分析了该江段仔稚鱼群落组成、优势种、密度变化、时间空间分布及其与环境因子的关系。结果表明:88d连续采样共鉴定出隶属于8目12科39个仔稚鱼类群, 其中37个类群鉴定到种, 1个类群鉴定到亚科, 1个类群鉴定到科。贝氏?(Hemiculter bleekeri)为该江段仔稚鱼的第一优势种, 其余优势种有虾虎鱼科(Gobiidae)、鳊(Parabramis pekinensis)和飘鱼(Pseudolaubuca sinensis)。仔稚鱼密度在7月1日达到峰值, 峰值为1230.77 ind./100 m3; 7月1日至8月15日仔稚鱼密度整体呈波动性下降的趋势。时间尺度的聚类将6个时期分为5月下旬—7月上旬与7月下旬—8月上旬2个群组, 贝氏?、翘嘴鲌和刀鲚等在6月下旬达到峰值; 鳊、四大家鱼和鳜等在7月上旬达到峰值。江段断面上南北近岸采样点仔稚鱼密度高于断面中心。使用冗余分析方法(RDA)分析了仔稚鱼密度与环境因子的关系, 发现水温、透明度、流量均为影响仔稚鱼群落结构的主要环境因子。水位与仔稚鱼密度相关性分析表明, 两者呈极显著相关(P<0.01)。研究表明, 湖口江段鱼类早期资源较为丰富, 仔稚鱼群落结构主要以中小型鱼类为主, 且江湖洄游性鱼类占比较高; 仔稚鱼对各环境条件有着不同适应特点, 仔稚鱼与水温、透明度、流量均呈现出不同程度的相关关系。研究结果补充了湖口江段鱼类早期资源的基础资料, 为长江中下游鱼类资源保护策略的制定提供了科学依据。

COMMUNITY CHARACTERISTICS OF LARVAE AND JUVENILE FISH IN HUKOU SECTION OF THE YANGTZE RIVER IN SPRING AND SUMMER

Hukou section, the connection between the Yangtze River and Poyang Lake for the migration route of many fish species, plays a vital role in the proliferation of fish. A systematic investigation on larval and juvenile fish resources were conducted during the fish breeding period in the Hukou section from May to August 2016. The community structure, dominant species, fish density, time-space distribution and their relationships with environmental factors in Hukou section were studied during the continuous 88-day investigation. A total of 39 larvae and juvenile taxonomic groups including 7 orders and 12 families were identified. Among them, 37 were identified to species level, one was identified to subfamily, and one was identified to family. Hemiculter bleekeri is the first dominant species and other dominant species are Gobiidae, Parabramis pekinensis, Pseudolaubuca sinensis. The larval and juvenile fish density reached its peak level on July 1 with 1230.77 ind./100 m3. The overall fish density showed a trend of decreasing volatility from July 1 to August 15. The cluster analysis divided 6 periods into 2 groups: Late May to early July in group Ⅰand late July to early August in group Ⅱ. Hemiculter bleekeri, Culter alburnus, Coilia nasus, etc. peaked in late June and Parabramis pekinensis, four famous domestic fishes, Siniperca chuatsi, etc. peaked in early July. The density of larval and juvenile fish on the south and north sides of the section were higher than that of the center section. Redundancy analysis (RDA) found that water temperature, transparency, and flow are the main environmental factors affecting the community structure of larval and juvenile fish. Correlation analysis showed highly significant correlation between water level and larval and juvenile fish density (P<0.01). This study indicates a large amount of fishes of early life history in Hukou section. The community structure of larval and juvenile fish is dominated by middle and small-sized fishes, and the proportion of river-lake migratory fishes are relatively high. Larval and juvenile fish have different adaptation characteristics to various environmental conditions. The species showed different degrees of positive and negative correlations with water temperature, transparency and flow. The results provide the scientific basis for the protection strategy of fisheries resource in the middle-lower reaches of the Yangtze River.