POPULATION DYNAMICS OF BOTHRIOCEPHALUS ACHEILOGNATHI (EUCESTODA: BOTHRIOCEPHALIDAE) IN JUVENILE GRASS CARP CTENOPHARYNGODON IDELLUS IN POND CULTURE IN SOUTH CHINA

摘要

The population dynamics of Bothriocephalus acheilognathi , a parasite in juvenile grass carp Ctenopharyngodon idellus (C. et V.) raised in a fish pond in South China, was studied in 1986, l987 and 1998 The tapeworm population in age 0 and over wintering age Ⅰ grass carp followed an annual cycle from its establishment to its decline, whereas age Ⅱ commercial sized fish was not affected. A high level of prevalence in winter led to a peak in early spring at 20.4 ℃ and a high level of mean intensity in the following months. When uninfected 0 group (1986) and age Ⅰ juvenile (1987) grass carp were introduced into the pond which kept the infected over wintering grass carp, their prevalence reached 93.1% and 96.9% respectively one month after infection. The prevalence of the tapeworm in over wintering and newly infected juvenile grass carp declined sharply in August and September at 28～33℃ and rose again to a minor peak in October. The mean intensity of 243.9 worms was observed in July. Cestode dispersion (S2/X) for 1986 and 1987 was > 1 from April to October. In the population structure from April to August, young worms < 1 cm dominated, maintaining 97.2%～98.2%. In November, the number of young worms decreased with the appearance of large sized gravid worms, which either vanished or remained in small numbers in December. The above findings provide a feasible basis for the control of bothriocephaliasis epizootics.