This study determined the optimal salinity for larval growth, survival and development of Penaeus semisulcatus. Protozoea 1 (PZ1) larvae were stocked in 2 l glass round bottom flasks in two replicates at 25, 30, 35, 40, 45, 50 and 55 ppt salinities and were fed live diets until the postlarval (PL) stages. The PZ larvae required an acclimation rate of 1 ppt per 15 min when exposed to a salinity change of over 5 ppt. The larvae displayed better tolerance to high rather than low salinities. The lowest and highest critical salinities appeared to be 23 ppt and 55 ppt, respectively. Early PZ larvae showed a high tolerance to hypersalinities but only for a few days. Although higher survival rates were obtained at high salinity levels (45-55 ppt), larval growth and development were better in lower salinities (25-40 ppt). Taking into account both survival and growth results, the optimal salinity for larval culture of P. semisulcatus inhabiting the eastern Mediterranean has been estimated to lie between 30 and 35 ppt. The present results demonstrate that P. semisulcatus larvae obtained from broodstock from the eastern Mediterranean can be successfully reared at 30-35 ppt until PL1/2 stages within only 6-7 days with a feeding regime of Tetraselmis chuii (20 cells/µl), Chaetoceros calcitrans (50 cells/µl) and Isochrysis galbana (30 cells/µl), plus 5 newly hatched Artemia nauplii/ml from M1 onwards, at 28°C
