Catches of postlarvae entering the estuary and of postlarvae and juveniles in the estuary showed strong seasonal variation; they were highest just before and during the wet season, from September to April each year. Catch rates often had a bimodal distribution each year. Total catches also varied substantially between years. Using multiple regression analysis, the most significant factor in determining the abundance of juvenile P. semisulcatus in the estuary was the number of benthic postlarvae that settled on the seagrass and algal beds. Rainfall was the most important environmental variable in the postlarval catch models.