COMMUNITY STRUCTURE OF THE DACTYLOGYRUS SPECIES ON THE GILLS OF WILD AND CULTRUED CRUCIAN CARP (CARASSIUS AURATUS)

The species and infection levels of Dactylogyrus on the gills of crucian carp (Carassius auratus) were investigated in Liangzi Lake and a fish cultured pond in Shishou city to determine the effects of the culture environment on the community structure of the Dactylogyrus species. Six Dactylogyrus species were identified on the gills of cucian carp in Liangzi Lake, including Dactylogyrus vastator, D. intermedius, D. arcuatus, D. baueri, D. formosus and D. inexpeatatus. With exception of D. inexpectatus, the other five species of Dactylogyrus were also found in the fish cultured pond. The mean abundance of Dactylogyrus species was higher in Liangzi Lake than that in the pond. Apart from D. vastator, the prevalence of other four Dactylogyrus species (not including D. inexpeatatus) in Liangzi Lake was higher than that in the fish pond as well. Mean richness, mean number of individual and Brillouins index were also higher in Liangzi Lake than that in the fish pond. The dominant species was D. arcuatus (0.54) in Liangzi Lake while D. vastator (0.76) in the fish pond. Of the factors affected Dactylogyrus community, such as fish density, population size, light and dissolved oxygen, dissolved oxygen was considered as the most important factor.