长江口沿岸碎波带仔稚鱼分布的季节性变动

Seasonal fluctuation of fish larvae and juveniles distribution in the surf zone of the Yangtze River estuary

为进一步探明长江口沿岸碎波带仔稚鱼种类组成和数量分布的季节性变化特征,2006年11月至2007年10月,在长江口沿岸碎波带的13个站位用小型拖网(1 m×4 m,网目1 mm)共采集到仔稚鱼77种,隶属于13目27科63属。各季节出现仔稚鱼种数分别为37、20、13和7种。仔稚鱼是以暖温性种类占绝对优势,按生态类型划分,河口性和淡水性种类为主,其次为海洋性种类,洄游性种类最少。根据优势度曲线可看出,夏季优势种最突出,秋季优势种最不明显。夏季与秋季的共有种最多,均为27种;冬季与春季,冬季与秋季间的共有种最少,均为11种。从数量分布来看,冬季仔稚鱼数量最少,且分布较分散,春季数量有明显增加,夏季数量达最大值,且分布趋于集中。在低盐和淡水的站位St.4、St.5、St.7和St.10,形成了以刀鲚为主要种类的仔稚鱼密集区,平均密度高达2 729尾/站。

To make a further clarification of the seasonal dynamms ot species composmon and abundance distribution of fish larvae and juveniles in the surf zone of the Yangtze River es- tuary, fish larvae and juveniles were collected at 13 stations by a seine net （1 m X4 m, 1 mm mesh-aperture） monthly from November 2006 to October 2007. There were 77 species of fish larvae and juveniles belonging to 63 genera in 27 families of 13 orders, in which Perciformes and Cypriniformes were the dominant families. The number of species collected in summer,spring, autumn and winter was 37, 20, 13 and 7 respectively. In all seasons, the warm-temperate spe- cies were absolutely dominant. In terms of the ecological types, the number of estuarine species was as much as that of freshwater species, followed by marine fish, and diadromous species was the least in ecological types. By analyzing the dominance curve of fish larvae and juveniles, we found that the dominance of species was the most prominent in summer, while not obvious in autumn. The shared species in different seasons showed more conformity between summer and autumn, but more difference between winter and other seasons. Catches varied significantly among seasons, peaking in summer with a mean of 1 132 ind./station. The abundance of fish larvae and juveniles was the least and the distribution was the most dispersive in winter, and increased dramatically in spring, then became more abundant and more concentrated in summer. The average density reached 2 729 ind./station, mainly composed of Coilia nasus, at the fresh- water or low salinity area of St. 4, St. 5, St. 7 and St. 10.