Community Structure Characteristics Of Coral Reef Area Fishes In Nanji Islands Marine Nature Reserve

In this paper, we studied the species composition, quantitative distribution,community structure, diversity and community stability of Nanji islands marine naturereserve coral reef area fishes according to the four seasons trawl survey datas in Nanjiislands marine nature reserve in April (spring), August (summer), November2011(autumn)and March2012(winter).We identified69species of fishes, including4species ofChondrichthyes fishes and65kinds of Osteichthyes fishes. Fish species number summer(52species)> autumn (37species)> winter (26species)> spring (23species),10speciesof fishes appeared in all four seasons, accounting for14.49%of the total. The Index ofRelative Importance（IRI） showed that the survey sea had no1specie of fish as dominantspecie in all the year round, only1specie of fish as dominant specie in three seasons,5species of fishes as dominant specie in two seasons, and6species of fishes as dominantspecie in one season, and the dominant species replacement rate r value showed that fishdominant specie seasonal succession phenomenon was very obvious. The average biomassand average abundance were not generally high in winter and spring, however, they weresignificantly higher in summer and autumn, the higher biomass area was in the open sea innorthwest direction of Nanji islands.NMDS analysis showed that the2d scale sequence diagram had a certain meaninginterpretation in spring, summer and winter three seasons, and it was a good sort in autumn.The community structure spatial variation was not obvious: CLUSTER analysis showedthat in the higher similarity level, spring, summer and autumn three seasons could bedivided into three different communities, winter could be divided into two differentcommunities; SIMPER analysis showed that the community characteristic species and thecommunity discriminating species in each season had larger similarity; the ANOSIManalysis results showed that there was no significant difference between some communities,but a significant difference between some communities in each season. SIMPER analysisand NMDS analysis showed that the community structure seasonal successionphenomenon was very obvious: different seasonal fish group similarity was not high, andno more than45%, the characteristic species result in similarity contribution rate was notthe same of different seasonal fish group; the seasonal dissimilarity between fish group wasspring-summer(94.97%)>summer-autumn(80.04%)>autumn-winter(76.55%)>winter-spring (63.72%). ABC curves showed that the Nanji islands coral reef area fishes four seasons’ fishcommunities subjected to various interferences, community structure tended to be unstable,the dominant species basically composed of relatively small individual fish.Species richness index (D) was highest in summer, then was in autumn,winter andspring were lower; evenness index (J’) had little seasonal variation, spring and autumnwere slightly higher than winter and summer; diversity index (H’) was not high,all werelower than2, its seasonal variation was basically the same as richness index (D), but thespring was slightly higher than the winter.