南沙群岛西南部海域鱼类群落结构分析

摘要

Nansha Islands is the most southerly,most reefs,most spread island in South China Sea;Nansha Island sea area of south 3°57′N,north to 11°55′N,west to 103°30′E,east to 117°50′E,which is made up of many reefs,beaches,islands,is a typical tropical waters;For the further study about this area,Third Institiute of oceangraphy,State Oceanic Administration carried out two surveys from 2012 to 2013 in southwestern waters of Nansha Islands;Fish community structure of the southwestern waters of Nansha Islands was analyzed according to two bottom trawl surveys carried out from 2012 to 2013.The survey received a total of 357 fish species,belonging to 27 orders,108 families and 219 genera,including 326 warm-water species and 30 warm-temperate water species.There are 7 dominant species(IRI＞ 500),such as Syna grops phili ppinensis 、Parascolopsis tosensis 、Synagrops serratospinosus and so on,most of them were small fish,with an obvious seasonal fluctuation.Analysis of the diversity index showed that Margalef index(D)changed in a large range and fluctuated seasonally(3.05～4.20);Shannon-Wiener index(H') didn't change significantly(2.31～2.69);Pielou index(J') kept consistent basically between spring and autumn(0.69～0.70).Results of replacement index and migration index showed that the fish community structure in autumn was less stable than that in spring and the community structure in the both seasons of them were the deviated ion from equilibrium.Simultaneously,we analyzed abundance biomass comparision curve,which showed the k-dominance curve of abundance were above either biomass curve in spring and autumn,the fast-growing,small individual species of r-selection was dominant in the community,the disturbance of community was a bit high and the stability of it was poor.The fish migration,different thermophili species move out and the supplement of reproducing populations,the individual growth,fishing,etc.are all the factors that affect the stability of the community.%南沙群岛是南海中最靠南、岛礁最多、散布最广的岛;南沙群岛海区南起3°57′N,北至11°55′N,西起103°30′E,东至117°50′E,由众多礁、滩、岛屿等组成,为典型的热带海域.为进一步研究该海域,国家海洋局第三海洋研究所在2012-2013年在南沙群岛西南部海域共开展了春秋2个航次的调查;根据该调查资料分析了该海域的鱼类群落结构.调查共获得鱼类357种,隶属于27目108科219属,其中暖水性鱼类327种,暖温性鱼类30种.优势种鱼类(IRI＞500)有菲律宾尖牙鲈(Synagrops philip pinensis)、土佐副眶棘鲈(Parascolopsis tosensis)、锯棘尖牙鲈(Synagrops serratospinosus)等5种,多为中小型鱼类,且季节间变化较大.分析多样性指数显示,南沙群岛西南部海域的Margalef种类丰富度指数(D)变化范围较大(3.05～4.20),两季间变化最为明显;Shannon-Wiener多样性指数(H')春秋两季间变动范围较小(2.31～2.69);Pielou均匀度指数(J')季节间基本保持一致(0.69～0.70);更替指数和迁移指数显示,秋季鱼类群落结构稳定性要低于春季,而且两个季节的鱼类群落结构都偏离平衡状态;同时分析数量生物量曲线显示,春秋两季的数量优势度曲线均在生物量优势度曲线之上,表明群落主要以生长较快,个体较小的r选择物种为主,群落受到的干扰程度较高,稳定性较差.鱼类的洄游、不同适温性鱼类的迁入迁出以及繁殖群体的补充、个体生长、捕捞等都是影响群落稳定性的因素.