长江口甲壳动物群落组成及其粒径结构研究

Study on community composition and size structure of crustaceans in the Yangtze River Ejstuary

为了解长江口水域甲壳动物群落状况,基于2020年11月(秋季)和2021年1月(冬季)、4月(春季)、8月(夏季)长江口拖网渔业资源调查数据,研究了长江口水域甲壳动物的种类组成、优势种、资源密度及生物多样性季节变化特征,并运用粒径谱及ABC曲线方法初步探究了长江口甲壳动物群落的粒径结构以及群落受扰动情况。结果显示,4个航次共鉴定出甲壳动物20种,隶属于2目11科,其中安氏白虾(Exopalaemon annandalei)、葛氏长臂虾(Palaemon gravieri)、脊尾白虾(Exopalaemon carinicauda)和三疣梭子蟹(Portunus trituberculatus)为优势种。甲壳动物资源密度夏季最高,冬季最低,资源密度空间分布整体上表现为长江口北支水域高于南支水域。根据生物多样性计算结果,秋季甲壳动物Shannon-Wiener多样性指数(H′)、Pielou均匀度指数(J′)和Margalef丰富度指数(D)均值高于其余3个季节,各季节多样性指数的高值区位于北支水域。粒径谱表明,长江口甲壳动物粒径范围最广的季节为秋季(-3~9),各季节生物量峰值位于0~4粒级,标准化粒径谱的拟合曲线均呈“穹顶”抛物线状,曲率范围为-0.13~-0.04。表征ABC曲线的W统计值变化范围为-0.21~-0.10,均为负值,表明长江口水域甲壳动物受到严重的外界干扰。研究结果可为长江禁捕前后的长江口水生生物资源状况评价提供基础资料。

The Yangtze River Estuary is located in the east coast of China.It has sufficient nutrients and bait resources,and provides spawning grounds and feeding grounds for many types of fish,shrimp,crab and other species.At present,most studies on fishery resources of the Yangtze River Estuary focuses on plankton,macrobenthos and fishes,while studies on crustacean community of the Yangtze River Estuary are relatively weak.In recent years,fish stocks in the Yangtze River Estuary have been severely reduced.As an important part of the Yangtze River Estuary ecosystem,it is very important to investigate and study the status of crustaceans.To improve the understanding of crustacean community,trawl fishery resource surveys were conducted in the Yangtze River Estuary.Based on seasonal survey data of 2020 and 2021,the community structure characteristics of crustaceans in the Yangtze River Estuary were analyzed.Size spectrum and ABC curve were used to study the size structure and disturbance status of crustacean community.The results showed that a total of 20 species(11 families and 2 orders)were captured during four voyages.Among them,four dominant species were identified,including Exopalaemon annandalei,Palaemon gravieri,Exopalaemon carinicauda and Portunus trituberculatus.Exopalaemon annandalei was the dominant species in spring,autumn and winter,and there was no common dominant species in spring and summer.A total of 9720 crustaceans were collected.The resource density of crustaceans was the highest in summer,with an average abundance of 108.29×10~3 ind·km~(-2)and average biomass of 169.78 kg·km~(-2).The resource density was the lowest in winter,with an average abundance of 23.96×10~3 ind·km~(-2)and average biomass of 26.46 kg·km~(-2).As for spatial distribution of resource density,the northern branch of the Yangtze River Estuary was higher than the southern branch on the whole.The ranges of Shannon-Wiener diversity index(H′),Pielou evenness index(J′)and Margalef richness index(D)of all stations of the crustacean community structure were 0-1.38,0-0.90 and 0-1.41 respectively.These three indices in autumn were higher than those in the other three seasons,and the highest values of diversity in each season were located in the northern branch of the Yangtze River Estuary.The range of size classes of crustaceans was the greatest in autumn(from-3 to 9),and the peak biomass of each season was in the range of 0-4 size class.The fitted curves for the normalized size spectrum were all dome-shaped,and the curvature ranged from-0.13 to-0.04.The W statistics representing ABC curve ranged from-0.21 to-0.10,all of which were negative values,indicating that the crustaceans in the Yangtze River Estuary were seriously disturbed and the community structure was in an unstable state.This study analyzed the community composition and size structure of crustaceans in the Yangtze River Estuary during the early period of fishing ban in key waters of the Yangtze River Estuary.It can provide research reference for the assessment of aquatic biological resources in the Yangtze River Estuary before and after fishing ban.