长江口邻近水域仔稚鱼分层群聚特征分析

Analysis on characteristics of stratified clustering of larvae and juveniles in adjacent waters of Yangtze River Estuary

利用长江口邻近水域2016年春季的仔稚鱼分层调查数据,分析了仔稚鱼的种类数、丰度、多样性和优势种的分层变化特征及其与温、盐度的关系。结果表明,共捕获仔稚鱼1548尾,平均每网捕获55尾。各水层的丰度值变化介于80.85~312.03尾·km^(−3),以50 m水层最大,30 m水层次之,15 m水层最小;种类数变化介于7~14种,从5 m水层至50 m水层呈持续增加的趋势。仔稚鱼的前弯曲期仔鱼期、弯曲期仔鱼期、后弯曲期仔鱼期和稚鱼期等4个发育阶段的丰度值均以50 m水层最大。水层从浅到深,种类数和丰富度指数持续升高,而多样度指数和均匀度指数则先增加后减小。根据相对重要性指数判断,5 m水层的主要种类有3种,其他水层的主要种类均有5种,主要种类在各水层的相对重要性指数存在一定差异。各水层之间的仔稚鱼种类数与盐度呈显著正相关关系(P<0.05,R=0.86),即随着水深增加和盐度升高,种类数也增多。在中上层水体,仔稚鱼丰度与水温之间存在极显著正相关关系(P<0.01,R=0.98);在中下层水体,仔稚鱼丰度与盐度之间存在显著正相关关系(P<0.05,R=0.79)。

Based on the stratified survey data of larvae and juveniles in the adjacent waters of the Yangtze River Estuary in spring 2016,we investigated the stratified variation characteristics of species number,abundance,diversity and dominant species of larvae and juveniles and their relationship with temperature and salinity.Altogether 1548 larvae and juveniles were caught with an average of 55 per net.The variation range of abundance value of each water layer was 80.85−312.03 ind·km^(−3),with 50 m water layer being the largest,30 m water layer being the smallest,and 15 m water layer being the smallest.The fish species number varied from 7 to 14,with a continuous increasing trend from 5 m to 50 m water layer.The abundance of larvae and juveniles in the four developmental stages was the highest at 50 m water layer.The species number and richness index showed a continuous increasing trend from shallow water to deep water,while the diversity index and evenness index increased first and then decreased.According to the IRI index,there were three main species at 5 m water layer.There were five main species at each of the other water layers,but there were some differences in their IRI index among different water layers.There was a significant positive correlation between the number of larval and juvenile fish species and their salinity(P<0.05,R=0.86).Thus,with the increase of water depth and salinity,the species number also increased.There was a significant positive correlation between the abundance of juvenile and water temperature in the upper and middle water(P<0.01,R=0.98);there was a significant positive correlation between the abundance of juvenile and salinity in the lower and middle water(P<0.05,R=0.79).