Fish community diversity analyses in the Yangtze River estuary, China

Abstract

Estuarine systems are considered as a typical ecotone,and an estuarine fish community study is consid-ered to be a fundamental ecological research study.Four facets(number of species,Pielou evenness,taxonomic distinctness and average taxonomic distinctness) of community diversity characteristics structuring by species level,abundance,binary data and classification levels were analyzed within the Yangtze River estuary,China,which is divided into three zones(Zone 1,Zone 2,and Zone 3) along the estuarine gradient.Fish sampling was conducted using bottom trawling seasonally from 2010–2011.The results showed that all four diversity parameters did not differ significant among seasons.However,number of species and average taxonomic distinctness both differed significantly among the different zones.An increasing trend in mean numbers of species from Zone-1(3.49 species)–Zone-3(10.13 species) was related to the stronger marine influence on the latter zones.Lower val-ues of average taxonomic distinctness in Zone-1 suggested that more species were closely related in Zone-1 than in Zone-2 or Zone-3,for example,8,20,and 19 families were recorded in Zone-1,Zone-2,and Zone-3,respec-tively.Although spatial changes in taxonomic distinctness and evenness were not significant,inverse patterns of the two parameters occurred.Nevertheless,evenness peaked in Zone-1 whereas more individuals were closely related in Zone-1 than in Zone-2 or Zone-3.Moreover,spatial patterns in community diversity were stronger than seasonal variations.This may reflect that salinity plays the major role in driving the estuarine fish community.This work analyzed the four facets of diversity estimations of fish community within the Yangtze River estuary,and further demonstrated that different measured parameters may highlight different information regarding com-munity structure,and will be useful for assessing estuarine fish community diversity.