حمیدرضا نوریزدان

In this study Different acclimation methods was investigated for post larvae of Litopenaeus vannamei to salinities above 40ppt in hatchery and its effect on the growth and survival of post larvae after the releaseing into culture ponds. Experiments were conducted during 2 periods of 12 and 30 days. In the first stage of the experiment, comparision of survival and growth rate of PL1 to PL12 to enhancement of salinity from 30 to salinities above 40ppt was done in seven treatments and three replicates in total randomized block design. In the second part, the best two treatments, based on the survival and growth rate, were selected and along with the control were placed in culture ponds for 30 days to assess their growth and survival rate. The highest survival rate (79.3%) was related to treatement 1 followed by treatement 7 and 5 with 78.6 and 77.3% respectively. There was no significant different between the control, 5 and 7 treatment (P>0.05). The lowest survival rate in the first experiment was belong to the treatment 4 with 70.6% which showed significant difference with control treatment (p<0.05). There was a significant difference between the survival rate of control and other treatments (P?0.05). As a result, 5 and 7 treatements with fewer salinity changes than other treatements, showed higher survival. The highest growth (4.4 mm) was belong to the control treatement followed by 3 and 4 treatement with 4.2 and 4.13 mm, respectively. But statistically no significant difference was observed (P>0.05). In the second experiment, in terms of survival, treatment 5 with 82.5% showed the highest survival rate and statically difference with control (P?0.05). In terms of growth, treatment 5 with 77.2mm and control treatment with 72.8mm showed the highest and lowest growth rate respectively, but no significant diference (P>0.05) was observed. Result of this study shows that if changes in salinity does not effect the survival and growth of the postlarvae if it is within the a