Silver ion and hydrogen peroxide act synergistically as a strong disinfectant. The purpose of this study was to assess the effect of combined hydrogen  peroxide 50% and silver ion 0.05% at four life stages of Indian white shrimp (Fenneropenaeus indicus) and to evaluate the feasibility  of using this substance in shrimp culture. The Trimmed Spearman-karber software was applied for determining ECso/96h and LC5o/96h with 95% confidence limit on the 6000 shrimp based on OECD static method.

The experiments were conducted  in Iran Shrimp Research Center, Bushehr,  during 2005 -2006. The

ECso values of 132.5, 67.89, 55.56, 51.95 and 48.6ppm were obtained in PL 15 stage after 12, 24, 48, 72

and 96 hours, respectively.  Also these were  147.57, 70.83, 60.01,  54.89, 41.19 for PL45 stage, and

306.43, 174.14, 113.62, 78.21, 61.96 for sub adult stage (12±1 grams), respectively. In addition, the EC5o values of243.25, 130.55, 75.56, 61.18 and 51.59ppm were obtained at adult stage (20±2 grams), respectively. The LC50 values of239.81, 101, 74.28, 65.72 and 61.45ppm were obtained in PL 15 stage

after 12, 24, 48, 72 and 96 hours, respectively. Also these were 304.56, 160.12, 113.1, 93.69, 79.38 for

PL4s stage, and 712.13, 518.44, 265.29, 145.53, 103.76 for sub adult stage, respectively. In addition, the LC5o values of 827.75, 508.91, 317.3, 139.44 and 85.88ppm were obtained at adult stage, respectively. The statistical results showed that the "no observed effect concentration" (NOEC) of this substance was 20ppm, and the "lowest observed effect concentration" (LOEC) was 40ppm, thus "maximum allowable concentration" (MAC) value was determined 28.8ppm on the Indian white shrimp. Therefore this combined chemical should be used under determined MAC value with a complete precautionary as a disinfectant for Indian white shrimp.