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

Abstract

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(IRI20),and the other species did not show any characteristics of the dominance(IRI0.05).20 fish species were recorded in the area of mudflat,the dominant species was the Mugil cephalus(IRI20),while the other species,including the Acanthogobius ommaturus,Taenioides rubicundus,Liza carinatus and the Collichthys lucidus had some characteristics of the dominance(20IRI10).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.