The ornamental fishery is expanding rapidly in the Red Sea, and concerns about the possibility of over exploitation were raised. Marine protected areas (MPAs) were addressed as a potential solution to prevent overexploitation. However, the sources of stock recruitment are not well understood. This thesis aims to reveal the genetic population structure and the demographic connectivity in the endemic fish species of the Red Sea Larabicus quadrilineatus, and in the two common fish species Chromis viridis and Pseudanthias squamipinnis.