THE GROWTH AND THE REPRODUCTIVE BIOLOGY OF EXOPALAEMON MODESTUS (HELLER, 1862) (CRUSTACEA, DECAPODA, PALAEMONIDAE) IN THE THREE GORGES RESERVOIR OF CHINA

We conducted monthly study on the growth and the reproductive biology of shrimp Exopalaemon modestus in the Three Gorges Reservoir from November 2012 to October 2013. The typical life span of the shrimp was 1214 months. E. modestus showed a clear sexual dimorphism in the body length, and the females were significantly larger in size than the males. The Von Bertalanffy growth function was estimated to be Lt=59.33-e-1.6(t+0.081) based on the frequency of the body length. The ovigerous females were monitored between early April and late October, and we found that the peak reproductive period was from mid April to mid June. The spawning populations included wintering and yearling individuals. The body lengths of the ovigerous females ranged from 27.07 to 53.71 mm, and the body length of 50% was estimated to be 37.06 mm. The overall sex ratio was 1.46:1 and females significantly outnumbered males. The absolute fecundity of E. Modestus ranged from 31 to 294 eggs (12753) eggs, meanSD, and the relative fecundity was (11522) eggs/g (meanSD). The absolute fecundity was related to the body length (FA=0.0031L2.8632, r=0.72, n=106) and the body weight (FA=104.63W+9.9534, r=0.79, n=106). The average diameter of the eggs of E. Modestus was (1215102) m (meanSD, n=4171). In order to properly protect and utilize the freshwater shrimp resources, we recommended to apply more strict management policies on shrimp harvest, for example, to reduce or forbid captures during the spawning season (April to September).