黄海鱼类功能群及其对浮游动物捕食的季节变化

Seasonal variations of the functional groups of fish community and their consumption of zooplankton in the Yellow Sea

用2006年9月-2007年8月对黄海中南部进行的5次断面调查,通过胃含物分析、聚类分析、功能群划分以及估算摄食量等方法,研究了黄海鱼类群落功能群组成及其对浮游动物摄食的季节变化。结果表明,黄海鱼类群落包括7个功能群,除初春以外,黄海鱼类群落主要以浮游生物食性功能群为主。春夏季的功能群组成简单,秋冬季的功能群组成变得复杂。黄海鱼类群落摄食的浮游动物种类主要有11种,春季摄食的浮游动物量最大,夏秋季逐渐减少,直至冬季摄食的浮游动物量最少,初春摄食的浮游动物量有所回升。不同季节摄食的浮游动物种类,以及摄食量都有较大差异,仅太平洋磷虾在各个月份的食物中均有出现,其余浮游动物饵料种类均是季节性的。

In the Yellow Sea,larger,higher trophic level,commercially important demersal species were gradually replaced by small,lower trophic level,pelagic,less-valuable species.Such transition inevitably leads to increase prey on low trophic level species,especially zooplankton.Therefore,it is an important means to discuss control mechanism of biological production in the marine ecosystem and to assess predation pressure on zooplankton.At present,there is still lack of systematic research on combination production of fish community with zooplankton at domestic and overseas.This paper aims to study seasonal variations of the functional groups of fish community and their consumption of zooplankton in the Yellow Sea.The fish samples,which accounted for 90% of total biomass,were collected during five bottom trawl surveys in the Yellow Sea in September,December 2006 and March,May and August 2007 which covered the range of 120.50°-124.53° E,31.77°-36.55°N.Except silver pomfret Pampus argenteus,the other 18 kinds of fish,3442 stomach content samples were analyzed.The prey items were weighed to the nearest 0.001 g after removing the surface water,and identified to the lowest possible taxonomic level.According to stomach content analysis results,cluster analysis and 60% of Bray-Curtis similarity level were used as criterion to divide functional groups of fish community.The results suggest that fish community in the Yellow Sea is divided into seven functional groups,i.e.,planktivores,shrimp predators,shrimp/crab predators,shrimp/fish predators,benthivores,piscivores and generalist predators.Except early spring,the dominant functional group of fish community in other seasons is planktivores.The composition of functional groups in spring and summer is simple,but the composition in autumn and winter becomes complicated.By estimating food consumption of zooplankton in each month,fish community in the Yellow Sea feeds mainly on 11 kinds of zooplankton,including Euchaeta marina,Corycaeus sp.,Calanus sinicus,Euphausia pacifica,Themisto gracilipes,Oxycephalus sp.,Sagitta crassa,Acetes chinensis,Maeruran larva,Brachyura sp.,and Squilla alima.The consumption of zooplankton prey is 218735 tons in spring,and is the largest consumption is all seasons,and then gradually reduces in summer and autumn.Zooplankton consumption come to the least amount in winter,and the consumption of zooplankton prey picks up in early spring.The kinds and consumption of zooplankton prey of fish community in different seasons have remarkable difference.Only Euphausia pacifica appeared in the food of fish in each month and the other kinds of zooplankton prey are seasonal.It is obvious that krill is most important zooplankton and occupies a very important position in the Yellow Sea ecosystem.So,the resource situation of krill in the Yellow Sea directly affects competition degree among planktivores.This study provides basic information for going deep into study on effect of zooplankton on dynamics of fish community at high trophic level.It emphasizes combination study between demand of fish production for zooplankton with biomass of zooplankton,and discussing the interaction mechanism between them.