南海北部海域夏季仔稚鱼种类组成和主要环境因子的关系

The relationship between species composition of fish larvae and juveniles and main environment factors in the northern South China Sea in summer

基于2012年夏季在南海北部海域设置的23个站位,以WP2浮游生物网(网口内径57 cm,网长271 cm,网目200μm)进行垂直拖网采集的样本,研究仔稚鱼的种类组成、数量分布,分析南海北部海域水文特征与仔稚鱼分布的相关关系。研究共采集仔稚鱼230尾,隶属11目33科77种,其中8种鉴定到科,23种鉴定到属,46种鉴定到种。鲈形目(Perciformes)种类最多,有16科24种,占调查海域仔稚鱼种类数的31.17%。其次是灯笼鱼目(Myctophiformes)和巨口鱼目(Stomiiformes),分别为1科18种和4科12种。灯笼鱼科(Myctophidae)、巨口光灯鱼科(Phosichthyidae)、钻光鱼科(Gonostomatidae)的仔稚鱼数量约占仔稚鱼总捕获量的50%。各站位间仔稚鱼种类数的变化,与丰富度指数的变化趋势较为一致。总体而言,粤东海域和琼东海域的仔稚鱼群落结构相对稳定。夏季南海北部琼东沿岸上升流海区、珠江冲淡水海区以及西沙群岛近岸海区仔稚鱼丰度相对较高。典型相关性分析(CCA)结果表明,南海北部仔稚鱼的数量分布与海表面温度(SST)和叶绿素a质量浓度(Chl.a)密切相关。聚类分析结果显示,仔稚鱼群落可划分为2个群组,大洋组和近海组。

The South China Sea is the largest semi-enclosed marginal sea in the Western Pacific.It is also a core area affected by the Southeast Asian monsoon.Due to its special geographic location,the hydrological characteristics are extremely complex in the northern South China Sea.In summer,driven by the southwest monsoon,there are seasonal coastal upwellings in the northern shelf of the South China Sea,which mainly include the coastal upwellings of East Guangdong and Qiongdong.In addition,the diluted water from the Pearl River Estuary with high nutrients also has an important impact on the ecological characteristics in the northern South China Sea.This study is based on the data collected from 23 stations set up in the northern South China Sea during summertime of 2012.The larval and juvenile fish samples were collected by the vertical trawl survey with WP2 plankton net(net diameter 57 cm,net length 271 cm,mesh 200μm).The species composition and quantity distribution of larvae fish and juveniles were studied,and the association between them and environmental factors was investigated,and the correlation between the hydrological characteristics of the northern South China Sea and the distribution and assemblages of fish larvae and juveniles was analyzed.A total of 230 fish larvae and juveniles were collected,belonging to 11 orders,33 families,and 77 species,of which 46 species were identified.The most diverse order was Perciformes,with 24 species in 16 families,accounting for 31.17%of the species of fish larvae and juveniles in the surveyed sea area.Followed by Myctophiformes and Stomiiformes,18 species in 1 family and 12 species in 4 families,respectively.The fish larvae and juveniles of Myctophidae,Phosichthyidae and Gonostomatidae accounted for about 50%of the total catch of fish larvae and juveniles.These results are consistent with the results of many previous surveys,which indicates that the species composition of fish larvae and juveniles in the South China Sea has not changed much.The changes in the number of fish larvae and juveniles among the stations in the surveyed sea area are more consistent with the change trend of the richness index(D).In general,the fish larval and juvenile fish community structure in the surveyed sea area is relatively stable.In summer,abundance of fish larvae and juveniles was related to environmental factors,such as temperature,salinity,chlorophyll-a mass concentration.Three peaks of the abundance were found,in eastern Hainan Island,where the coastal upwelling occurred,the diluted water from the Pearl River,and coastal water of the Paracel Islands.At the same time,the canonical correlation analysis(CCA)results also showed that the temporal and spatial distribution of fish larvae and juveniles in the northern South China Sea is closely related to surface sea temperature(SST)and chlorophyll a(Chl.a)mass concentration.Cluster analysis showed that the fish larvae and juveniles assemblage could be divided into oceanic group and offshore group.