[Reproductive biology of Macrobrachium nipponensis in Lake Wuhu]

Macrobrachium nipponensis is a key species of freshwater shrimps in China. To know its reproductive biology is very important for its protection and rational use. Studies from September 1998 to September 1999 in LakeWuhu showed that the spawning ground of M. nipponensis was situated in the littoral zone of the whole lake. The main spawning period of overwintering shrimps was from mid-April to mid-July (water temperature 20.5-31 degrees C), and that of non-overwintering shrimps was from mid-July to mid-September (water temperature 31-23 degrees C). The sex ratio (female:male) increased gradually during the spawning period, and the absolute fecundity of overwintering shrimps was higher than that of non-overwintering ones. The relationship between absolute fecundity and body length and between absolute fecundity and body weight could be expressed as cubic equation and simple linear equation, respectively. The relative fecundity (RW) of M. nipponnensis could regard as a constant, and its 95% confidence limits was 1067.76 +/- 16.94 eggs.g-1.