长江口中华鲟自然保护区底层鱼类的群落结构特征

根据2004年8月、11月和2005年2月(Ⅰ年度)、2005年8月、11月和2006年2月、5月(Ⅱ年度)、2007年8月、11月和2008年2月和5月(Ⅲ年度)对长江口中华鲟自然保护区15个站位点的底拖网调查数据,对该水域的底层鱼类群落结构特征及时间和空间变化规律进行了分析。结果表明,调查中捕获底层鱼类42种,隶属于13目24科39属。底层鱼类的种类组成和群落结构进行聚类分析,15个站位聚合成两大类群,类群A位于南支北港和北港北沙近东滩水域,共出现20种底层鱼类,主要以淡水性和河口性鱼类为主;类群B位于北支和北港北沙近外海水域,共出现鱼类39种,主要以河口性和海洋性鱼类为主。ANOSIM和SIMPER分析表明底层鱼类群落结构不同季节间差异显著,造成这种趋势的主要原因可能是与棘头梅童鱼(Collichthys lucidus)和凤鲚(Coilia mystus)的繁殖和索饵洄游有关。

Community structure of demersal fish in Nature Reserve of Acipenser sinensis in Yangtze River estuary

Chinese sturgeon, Acipenser sinensis, listed among the first class of protected animal in China, is an anadromous fish, which as present understood, is distributed in the East China Sea, Yellow Sea and the main channel of the Yangtze River.In autumn, larvae, after hatching in the upper reach of the Yangtze River, begin to swim downstream along the main channel of Yangtze River. Juveniles gradually reach the Yangtze River estuary (hereafter abbreviated as YRE) from May to June of the next year, in where juveniles spend almost 3 months on foraging and other physiological adaptation for entering into the sea. The small-sized demersal fish in YRE are the main food resource for juveniles. So, it is very important to understand the community structure and its variation feature of demersal fish in YRE for protecting this endangered species effectively. We designed 15 sampling sites (Z1-Z15) in the Nature Reserve of A. sinensis in YRE. The sampling sites are located at 121°32.08'-122°11.65'E, 31°19.58'-31°38'N, where is the major foraging ground for juvenile Chinese sturgeon. All the sample sites were divided into 3 sections based on the location in YRE and water salinity, i.e. South Branch-North Channel (Z1-Z3) with average salinity of 0.40, North Branch (Z4-Z10) with average salinity of 20.00 and North Sha in the North Channel (Z11-Z15) with average salinity of 1.21.Demersal fish were collected for analysis from all the sampling sites by using bottom trawl every three month from August 2004 to May 2008. In this study, totally 42 fish species, belonging to 13 orders, 24 families and 39 genera were found in the survey area. The fish community includes 4 ecological types, i.e., freshwater fishes (6 species), marine fishes (23 species), estuarine fishes (10 species) and migratory fishes (3 species). The species composition and community structure of demersal fish were approached by using the multivariate analysis software PRIMER, of which CLUSTER and MDS (Non-metric multidimensional scaling) were adopted. Fifteen sampling sites were separated into two groups (A and B). Group A was located in the South Branch-North Channel and inshore waters of North Sha in the North Channel, with 20 species which give priority to freshwater and estuarine fishes. Group B was located in the North Branch and offshore waters of North Sha in the North Channel with 39 species, mainly including estuarine and marine fishes. SIMPER (Similarity Percentages) test and further ANOSIM (Analysis of Similarities) test indicated significant seasonal changes in the community structure of demersal fish because of influence from breeding and feeding migration of Collichthys lucidus and Coilia mystus.