长江河口潮间带盐沼植被分布区及邻近光滩鱼类组成特征

研究鱼类群落在不同生境中的差异或者变化,是评价与预测生境丧失、环境退化等对湿地生物多样性与生态系统功能影响的重要基础。2006年4—11月,在长江河口崇明东滩盐沼植被分布区(简称草滩)和邻近的光滩区域分别设置采样站位,每月大潮期采用定制插网对鱼类群落进行了取样调查。分析研究了长江河口潮间带盐沼植被分布区和邻近光滩区域的鱼类组成及其月际变化,并对影响鱼类分布的主要因子进行了探讨。调查期间共采集鱼类标本1638尾,分属9目14科22种;其中,淡水鱼类2种,定居性河口鱼类12种,海洋鱼类5种,洄游鱼类3种。植被分布区和光滩区域鱼类组成及优势种特征存在明显差异。调查期间,植被分布区记录鱼类13种,主要优势种为斑尾刺虾虎鱼(Acanthogobius ommaturus)、鲻(Mugil cephalus)和棱鮻(Liza carinatus)(IRI>20),其他种类基本不具有优势度特征(IRI<0.05);光滩区域记录鱼类20种,主要优势种鲻(IRI>20),其他包括斑尾刺虾虎鱼、狼牙鳗虾虎鱼(Taenioides rubicundus)、棱鮻和棘头梅童鱼(Collichthys lucidus)也具有一定的优势特征(20>IRI>10);两个区域共有种为11种,部分种类只出现在光滩或植被分布区,但主要优势种均为定居性河口鱼类。与世界其他河口盐沼湿地鱼类研究结果不同的是,光滩区域记录的鱼类物种数、个体数、生物量和整体物种多样性水平均高于植被分布区;光滩和植被分布区鱼类相应的量比关系存在明显的月际变化,但两种生境鱼类组成间的关联性和差异性均不显著。通过比较两种生境共有的优势种体长发现,长江河口盐沼植被分布区鱼类优势种的平均体长大于光滩区域,而且植被分布区部分优势种体长的上、下限范围也大于光滩区域。长江河口盐沼植被分布区,除了育幼场外,还是许多鱼类成鱼的重要栖息地。影响河口潮间带盐沼湿地鱼类组成与分布的主要因素包括鱼类自身的生物学与生活史特征、饵料生物的组成与分布、植被出现与表形特征等生物因素和水温、盐度、淡水径流、潮汐特性等非生物因素,其对长江河口潮间带盐沼湿地中鱼类群落的组成与分布的综合作用机理有待进一步研究。

Characteristics of the fish assemblages in the intertidal salt marsh zone and adjacent mudflat in the Yangtze Estuary

The knowledge about the difference or variation of the fish assemblages among the different habitats is an important basis for assessing and predicting the impacts of habitat loss or environment degradation on the wetland ecosystems. The salt marsh in the Yangtze Estuary is facing the threat of erosion and degradation due to the reduction of the annual sediment supply from the Yangtze River. However, the variation of fish assemblages among different habitats of intertidal salt marsh zone and its adjacent mudflat in the region are poorly understood. In 2006, 2 permanent sampling sites were established in Scirpus mariqueter salt marsh and its adjacent mudflat on the intertidal zone of Chongming-Dongtan that is one of the largest salt marshes in the Yangtze Estuary. Based on monthly trap net surveys of fishes during spring tides from April to November, the characteristics of the fish assemblages in the different habitats, including the salt marsh and mudflat, and the monthly variations were analyzed. A total of 1638 specimens of fishes were collected, belonging to 9 orders, 14 families and 22 species, which included 2 freshwater species, 12 resident estuarine species, 5 marine species and 3 migratory species. The characteristics of the fish assemblages, including the dominant species, were different in these two different habitats. 13 fish species were recorded in salt marsh,of which the dominant species were the Acanthogobius ommaturus, Mugil cephalus and Liza carinatus(IRI>20),and the other species did not show any characteristics of the dominance(IRI<0.05). 20 fish species were recorded in the area of mudflat, the dominant species was the Mugil cephalus(IRI>20), while the other species, including the Acanthogobius ommaturus, Taenioides rubicundus, Liza carinatus and the Collichthys lucidus had some characteristics of the dominance (20>IRI>10). The major dominant species in the different habitats were all resident estuarine species. The results from the Yangtze Estuary were different to those from the other regions in the world. The number of species and individuals, biomass and the species diversity of the fish assemblage recorded in the area of the mudflat were all greater than those in the salt marsh. The quantitative characteristics of the fish assemblages, including the number of species and individuals as well as biomass, varied monthly and in different habitats, while the largest difference was the body length. The mean value and the extent of minimum and maximum values of the body length for some dominant species were greater in the salt marsh than in the mudflat. The salt marsh was not only the nursing area for the juvenile fishes, but also an important habitat for the adults. Various factors influence the composition and distribution of the fish assemblages, including the biotic factors such as its biological characteristics and life history, the composition and distribution of prey, presence and morphological characteristics of the vegetation, and also the environmental factors such as water temperature, salinity, fresh water inflow and tidal regime, etc. Further studies are need to investigate the mechanisms that all these factors operate together upon the fish assembles in the intertidal wetlands in the Yangtze Estuary.