Abstract:The effects of culturing in stages on the growth of shrimp Litopenaeus vannamei and the water quality were investigated from April to July in 2015. Experiments were conducted in 6 shrimp culturing ponds (2650 m2, 53 m×50 m each). The shrimp was first cultured in 2 ponds with a density of about 300×104 ind/hm2 for early cultivation. The subjects were stocked at 3 culturing time points, 36, 48 and 83 days, and were referred to as T1, T2, and C groups respectively. After early cultivation, the shrimp in the T1 and T2 groups were divided into two ponds with a suitable density (60×104 ind/hm2). The survival rate, the growth of shrimp, and the water quality were evaluated during the experimental period. The growth increment of weight and length during the first week was significantly boosted and the specific growth rate (SGR) for T1 and T2 reached 9.36 %/d and 6.36 %/d respectively. The T1 group showed the highest SGR and food consumption during the experiment, and the feed conversion ratio (FCR) was higher in T1 (1.053) than in T2 (0.822). In most of the divided culturing periods, the T2 group maintained a higher SGR. Compared to the T1 and T2 groups, the C group had lower concentrations of NH4+-N and NO2--N, a higher level of total particle matter (TPM), and a lower content of Chl-a. The T2 group had the highest Chl-a content. These results indicated that the shrimp might achieve rapid growth later if divided into different ponds after a proper cultivation period (48 days). The organic matter accumulation in the pond decreased in the early cultivation, which helped improve the water quality of the pond. However, the water quality may worsen when the feed consumption in the pond reached a certain level in unit time. In conclusion, divided culturing in the different ponds could improve both the growth of shrimp and the water quality.
