长江口银色鳗的形态指标体系及其雌雄鉴别

Analysis of morphological index system and discrimination of male and female silver eels(Anguilla japonica) collected at the Yangtze River Estuary

测定和分析了2007年和2008年的10-11月间采自长江江苏靖江段(32°01'27″N,120°25'56″E)的153尾银色鳗的形态学性状,建立了雌雄个体的判别模型。对16个直接测量性状的主成分分析和17项标准化比例性状的R-聚类分析,均显示长江口银色鳗的个体差异主要集中在体形大小和头部特征,吻部前端细部特征,以及眼径和胸鳍大小等3个方面。在此基础上,通过逐步判别法从75尾样本的17项标准化比例性状中筛选出5个比例性状,即丰满度、垂直眼径/头长、体高/体长、水平眼径/头长和吻形,所建立的判别方程,对群体识别的正确率为89.3%。利用其余78尾银色鳗样本对这一判别方程进行识别验证,识别的正确率达的88.5%。ANOVA分析显示,除了吻形,组成判别方程的其他4个标准化性状在两性群体间均存在着极显著的差异(P<0.001),表明长江口银色鳗的雌性个体比雄性更为丰满,体型较高,但眼较小。

Anguilla japonica is one of the most important commercial catadromous species in Asia.Yangtze River Estuary serves as the major production area of larval eels and the only fishery waters of adult eels in China.In this study,we analyzed biological information for 153 migrating silver eels collected at Jingjiang reach of Jiangsu Province（32°01＇27″N,120°25＇56″E） from Oct.to Nov.in 2007 and 2008.Based on the analysis of the morphological index system of Japanese eels with Principal Components and R-cluster Analysis the reults indicated that A.japonica could be classified by ＂body size and head feature＂,＂detail characteristics about the anterior part of snout＂and＂eye diameter and pectoral fin size＂.On the basis of this analysis,17 characteristics were normalized and further used for stepwise discriminant.And then 5 characteristics were picked out： fatness,vertical eye diameter/head length,body depth/body length,horizontal eye diameter/head length,snout shape.Thus the discriminant equations were built for classifying 75 samples and the accuracy rate was 89.3%.Furthermore,the other Japanese silver eels were also classified by this model and the success rate was 88.5%.ANOVA analysis showed that,apart from snout shape,the other four standardized characteristics between male and female populations were significantly different（P 0.001）.Therefore,we concluded that the female silver eels collected from Yangtze River estuary were superior to males in the respect of fatness and body depth but smaller in eye diameter.