Seawater (SW)-acclimated Nile tilapia, Oreochromis niloticus, can tolerate up to 30-ppt SW but rarely produce offspring. The embryos of SW-acclimated O. niloticus survived equally well from 0- to 10-ppt environment but not under 20 ppt. However, when the embryos were incubated under 10 ppt during days 0-3 and then the salinity was suddenly shifted to and maintained at 20 ppt during days 4-6, their survival rate was comparable to those incubated under 0 and 10 ppt. To elucidate a molecular adaptation of the embryos that survived different salinity environment, the proteomic profiles of the newly hatched embryos, or early larvae, hatched under 0 ppt, 10 ppt, and those being incubated at 10 ppt during days 0-3 followed by at 20 ppt during days 4-6 were compared.