Fish Community Structure And Correlation To Major Environmental Factors In Yangtze River Estuary

Based on tidal net and bottom trawl, the fish community was investigated inYangtze River estuary in2010. The study comprehensively summarized the fishcommunity structure and temporal and spatial variation, analyzed the correlationbetween fish community structure and vital environmental factors, and preliminarilyevaluated the habitat suitability of fish in Yangtze River estuary, using some biostatisticsmethods, for example, Cluster, MDS, SIPMER, PCA, CCA, etc.1. To investigate the use of fishes on the intertidal water area, tidal net was carriedout on the intertidal water area in Yangtze River estuary, in May, August and November2010, respectively. A total of28species of fish which belong to16families and10orders were collected. The species number of Cypriniformes had the maximum value,followed by those of Perciformes. The dominant species were Lateolabrax maculates,Liza haematocheila and Cynoglossus gracilis. Fish communities were classified into6ecological guilds of estuarine species, marine stragglers, catadromous species,anadromous species, marine migrants and freshwater species. Estuarine species andmarine migrants were at the distinct advantage. The intertidal fish community wasclassified into autumn and spring-summer groups by cluster analysis. Lizahaematocheila, Lateolabrax maculates, and Acanthogobius ommaturus contributedlargest to the seasonal differences. PCA based on fish abundance of species andenvironment factors indicated the alternating seasonal variation of temperature andsalinity caused the seasonal changes in fish community structure. PCA based on fishabundance of ecological guilds indicated that the community characteristic of summerfish was mainly determined by marine migrants and the community characteristic ofautumn fish was determined by estuarine species. It is inferred that, for those marinemigrants and estuarine juvenile fishes, feeding and growing in the intertidal water areaof different seasons was the main reason for the significant seasonal differences.2. To understand the temporal and spatial variation of the fish community structure,bottom trawl was carried out in the subtidal water area in Yangtze River estuary, inMarch, May, August and November2010, simultaneously, investigating thehydrological condition. A total of28species of fish which belong to13families and9orders were collected. The species number of Perciformes had the maximum value,followed by Clupeiformes. But the abundance of Clupeiformes was the highest, followed by Perciformes. The dominant species were Coilia ectenes, Collichthys lucidus,Odontamblyopus rubicundus and Cynoglossus gracilis. There were five ecologicalguilds during the survey. Anadromous species and marine migrants were at the distinctadvantage. Fish communities were classified into winter, South Branch-North Channeland North Sha in the North Channel of summer, North Branch of spring, North Branchof summer and autumn. Coilia ectenes, Collichthys lucidus and Odontamblyopusrubicundus contributed largest to community differences. The anadromous species andmarine migrants which had different advantages on temporal and spatial scales causedto the significant temporal and spatial differences in the subtidal area. CCA indicatedthat pH, turbidity, temperature and salinity had the most important effects to thedistribution of the fish community. The significant seasonal differences were caused bythe response of fish to the temperature, and the bias of fish to the salnity led to thesignigicant spatial differentces. Comparing to the history record, Collichthys luciduswas totally dependent on the Yangtze River estuary as the area of nursery or spawning.3. To preliminarily evaluate the choice preference of fish habitat in the YangtzeRiver estuary, juveniles Collichthys lucidus which was the dominant species in springwas selected. Indexs of the habitat suitability curves of juvenile Collichthys lucidus,including Pseudograpsus albus, salinity, sediment and depth, were estabilished, theweights of indicator factors were determined by AHP. Meanwhile, the habitat suitabilityindex of juvenile Collichthys lucidus at each site was calculated using IFIM. The resultsindicated that HSI was more than0.5in North Branch, and less than0.2in SouthBranch. Collichthys lucidus spawned in the inshore waters, then swimming to theoffshore ocean. It indicated that Yangtze River esturay is the nursery and spawning areaof Collichthys lucidus, which were consistent with HSI. Two biological factors hadbetter positive correlation with juveniles Collichthys lucidus abundance which indicatedthat biological factors could be characterized the response of juveniles Collichthyslucidus to environment, and speculated that food competition was not emerged betweenthem. CODMn, NH4+-N, TP and VH did not have significant correlation with the fishabundance, which NO2--N, NO3--N and TN had significant positive correlation with, itsuggested that water pollution of the survey area had not been damaged to the fishhabitat. However, Cu and Cd had significant negative correlation with the fishabundance which indicated that the heavy metal pollution had harmed the growth anddistribution of juveniles Collichthys lucidus. It inferred that the heavy metal was beingthe restrictive factor which influenced the fish habitat in Yangtze River estuary.