Abstract:

Based on the fishery survey by setting net from March 2009 to February 2010,the community structure,dominant species composition and biodiversity of smallsized fishes have been analyzed.24 species of smallsized fishes were collected,which belongs to 5 orders,7 families，and most of the species were belong to Cypriniformes.The dominant species were 〖WTBX〗Hemiculter bleekeri,Coilia nasus,Cynoglossus trigrammus，Saurogobio dabryi〖WTBZ〗 and 〖WTBX〗Pelteobaggrus nitidus,〖WTBZ〗which occupied  8344% of the total catch in number,and 8202% of the total weight.〖WTBX〗Hemiculter bleekeri〖WTBZ〗 and 〖WTBX〗Cynoglossus trigrammus 〖WTBZ〗were the dominant species in each season,and 〖WTBX〗Coilia nasus〖WTBZ〗 in spring,summer and autumn.Four diversity indexes,ShannonWiener’s index (H’),Margalef’s index(R’),Pilou’s index(J’),McNaughton’s index(Dn),were calculated by catch in number to analyze the characteristics of species diversity of fishery communities.The intermonthly range of  H’values was 118 to 176, R’was 087 to 207, J’ was 048 to 083 and Dn was 057 to 086.Based on research sets by season,in spite of any calculation unit，both by quantity and by weight，the highest value of R’ and Dn was in spring while the lowest was in winter, and the highest value of H’ and J’ were all present in winter while the lowest were in summer.Various factors  affecting the smallsized fishes resources in this reach were discussed,and several suggestions of how to develop and protect smallsized fishey resources were provided