东海生态系统中鱼卵、仔稚鱼种类组成、数量分布及其与环境因素的关系

为了解当前东海生态系统中鱼卵、仔稚鱼种类组成和数量分布的现状及其变化与物理环境因素的关系,根据2006年11月—2008年6月5个航次的鱼卵、仔稚鱼和物理环境调查资料,对鱼卵、仔稚鱼种类组成、数量分布与产卵场物理环境进行分析,探讨不同季节、不同年份鱼卵、仔稚鱼种类组成和数量分布的变化及其与物理环境的关系。结果显示,5个航次采集到74 813粒鱼卵、16 826尾仔稚鱼,共有135个种类。其中,鉴定到种的有109种,隶属于15目67科99属,还有17个种类仅能鉴定到属、6个种类仅能鉴定到科和3个种类仅能鉴定到目。2006年—2007年秋季、冬季和春季鱼卵、仔稚鱼的种类和数量随着季节变化逐渐增多;2008年春季的种类和数量较2007年春季明显偏少;2008年初夏种类的数量与2008年春季基本相近,但鱼卵的数量明显增多,仔稚鱼的数量基本相近。42种优势种类、重要种类和主要种类构成当前东海生态系统中鱼卵、仔稚鱼种类组成的主要成分。东海表层水温和盐度分布有显著的季节变化。秋、冬季表层水温锋面强度最强,春季次之,初夏最弱;锋面的位置秋季离岸最近,冬季次之,春季和初夏离岸最远,冬季偏南,初夏季节北移。表层盐度锋面主要分布在近岸区域,与岸线大致平行,其强度冬季最强,春、秋季次之,初夏季节最弱。秋、冬季节陆架深水海域的水温较沿岸海域高,鱼类生殖群体在陆架深水高温区产卵;春季和初夏季节沿岸海域明显升温,鱼类生殖群体由深水区向近岸海域进行生殖洄游,产卵场分布由陆架中部向近岸海域扩展,并在近岸海域形成了中心产卵场。鱼卵和仔稚鱼的分布与温、盐锋面和种类的温、盐属性的关系密切,主要分布在温度锋面暖水一侧,并有各自最适宜的温度和盐度范围。水温、盐度与种类的繁殖生物学特性是导致鱼卵和仔稚鱼种类组成与数量发生变化的主要因素;适宜的温度和盐度范围、锋区的辐聚和卷夹作用以及种类的生物学属性是影响鱼卵和仔稚鱼数量分布以及密集分布区形成的主要因素。

Species composition and abundance distribution pattern of ichthyoplankton and their relationship with environmental factors in the East China Sea ecosystem

In order to understand the species composition and abundance distribution pattern of fish eggs and larvae in the East China Sea ecosystem and their relationship with physical environmental factors,based on the data of five ichthyoplankton and physical environment surveys in the East China Sea in different seasons during November 2006 to June 2008,the seasonal and inter-annual variation of species composition and abundance distribution pattern of fish eggs and larvae,and the seasonal and inter-annual variabilities in physical environment of spawning grounds and their impacts on the distribution pattern of the spawning grounds,species composition and abundance distribution patterns of fish eggs and larvae have been discussed.The result showed that a total of 74 813 fish eggs and 16 826 fish larvae belonging to 135 taxa were collected,of which,109 taxa have been correctly identified to species level,which belong to 99 genera,67 families and 15 orders;while 17 taxa can only be identified to genus level,6 taxa only identified to family level and 3 taxa identified to order level.There was a tendency toward increased species number and amount of fish eggs and larvae from autumn,winter to spring during 2006 to 2007;whereas,the species number and amount of fish eggs and larvae for samples collected in spring 2008 were significantly lower compared to those collected in spring 2007.Though the species number of fish eggs and larvae for samples collected in spring 2008 were almost the same as in early summer 2008,the amount of fish eggs were significantly larger in early summer compared to spring,on the contrary,the amount of fish larvae in early summer were almost the same as in spring 2008.Species composition of the forty-two dominant species,important species and main species are the major components of fish eggs and larvae distributed in the East China Sea currently.Studies of the physical environment in the East China Sea showed that changes in patterns of sea surface temperature and salinity were markedly different among seasons.In the research domain,the order in which the sea surface thermal front intensity varied with seasons from the strongest to the weakest was autumn-winter,spring and early summer;the distance from the frontal areas to the coastal also varied with seasons from the nearest to the farthest was autumn,winter,spring and early summer,meanwhile the frontal areas run southward in winter and run northward in summer.The sea surface saline front mostly lies close to the shore and usually runs parallel to the shoreline.The surface saline front intensity varied with seasons,most visible in winter,whereas some wane in early summer before regaining strength in autumn.The autumn-winter water temperatures in deep shelf sea areas were higher than coastal waters,and then the spawning stock moved to offshore deep-warm waters and spawned there.The water temperature in coastal waters remarkably increased in spring and the highest value was recorded in the early summer.Then the spawning stock exhibited some form of an inshore spawning migration,and the spawning ground expanded from deep shelf sea areas to coastal waters and formed inshore spawning centers.The abundance distribution patterns of the fish eggs and larvae were closely related to the surface thermal and saline fronts,also species-specific temperature-salinity tolerance.In general,fish eggs and larvae were distributed according to the spreading of the warmer surface waters and gathered at the warm side of the thermal front,with species-specific optimal temperature-salinity.Ocean environmental conditions such as temperature and salinity,and the reproductive biology of each species were the main causes of variation in species composition and distribution patterns of fish eggs and larvae among different surveys.Optimal temperature-salinity range,convergence and entrainment in the frontal area and the biological characters of the species all play the importand role in the formation of high density areas of fish eggs and larvae.