Threadfin fish (Polynemus paradiseus) is one of the native fish species which has been considered potential candidate for aquaculture because it has high meat quality and high economic values. So, study on P. paradiseus was carried out from July, 2012 to December, 2013. Samples were collected monthly at least 30 individuals at four sampling sites belonging to Hau River including Thot Not, Ninh Kieu (Can Tho City), Đai Ngai and Tran Đe (Soc Trang province). Specimens were caught in natural water bodies by fisherman and local markets. They were kept in cool condition (at 4oC) and transferred to the Lab of Faculty of Fisheries, Cantho University to be stored (at ? 20oC) and analyzed. The results revealed that fecundity of tthreadfin fish is low. Diameter of egg from the females which gonad development at stage IV is 6.02±0.6 mm. In Hau River, P. paradiseus spawn mainly from March to June, and December to January.

Key word: Threadfin fish, Propagative biology, Hau River.