The Comparative Study On The Larval Culture Of Penaeus Vannamei Fed Microencapsulated Diets

Microencapsulated diets has been widely recognized as a kind of fairly ideal feed for rearing larvae of shrimp, for it contains the characteristics of rich nutrition, good flavour and soud stability .The comparative experiments of rearing Penaeus vanname larvae fed the microencapsulated diets and micro-partical diets of "OK" brand and a searies of microgranular diets of "Bonasse" brand was performed. Two brands of diets are respectively formulated with rotifera at percentage of 70%, 80%, 90% and 100%. During the nursery period, the water quality factors such as the concentrations of NH3-Nt, NH3-Nm, NO2- - N, COD and main planktons were tested to find out their change regulation and the influence on survival rates and metamorphic rates of shrimp larvae. The results showed that the concentrations of NH3-Nt, NH3-Nm, NO2- - N tend to increase during nursery period, however, COD tended to increase until M3 period, and then began to fall. The predominate planktons in nursery water were Skeletonema, Puyrrop Hta and Euplotes sp. The nursery water was the best, when microencapsulated diets of "OK" and rotifera were blended at the percentage of 80% and 20%, the nursery water quality was the best during the rearing period, the highest concentration of NH3-Nt (NH3-Nm) was 1.025mg/L (0.0836mg/L) ,and the highest concentration of NO2-- N was 0.0236mg/L. When larvae emerged, the concentration of COD was 1.526mg/L, Puyrrop Hta was 1000 Entries/ml, and the metamorphic rates of all periods exceeded symmetrically 97%, and the survival rates also higher than the control group fed pure crude diets. The emergence status in P7 period was described as follows: the metamorphic rate: 73.33%; the average tail weight: 2mg; average body length: about 7.604mm; which were 18.30%, 19.3%, 8.4% higher than that of control group respectively. All emergence index were higher markedly than control group (P<0.05) , besides, the shrimp larvae showed high quality anduniformity, the amount of "OK" brand that was used in every group during cultivation was 48.34%,58.50%,48.81%,and 49.5% less than that of "Bonasse" brand, however, the former had the better larval nursery effect than the latter obviously. It was more recommendable that using the compound blended with formulated diet of 80% microencapsulated diets of "OK" brand and 20% rotifera than only using microencapsulated diets of "OK" brand. Because the emergence rate , the average tail weight and average body length casted at the proportion as the former, were 38.73%,25% and 7.8% higher than that casted with the latter, so as all kinds of emergence index (P<0.05) . The results show that the rearing larvae of Penaeus vannamei is related to both the water quantity change and the change of ponds, expecially to the kind and the amount of diets. During the microencapsulated diets used, diets of "OK" brand are better than that of "Bonasse" brand. The diet blended with 80% "OK" brand and 20% rotifera is the best.