The comparison of the chemical properties of semen of black porgy Acanthopagrus schlegelii long-term acclimated reared in freshwater (BFW) and seawater (BSW) with sperm activity of salinity and ion composition. The chemical properties of seminal plasma on BFW of the factors that most there was not significant difference in the BSW. However, osmolality in seminal plasma of BFW and BSW was $307.0{pm}4.6$ and $337.3{pm}10.1$ mOsm/kg, respectively, where BFW showed significant lower concentration in contrast to BSW. Salinity effect on sperm motility of BFW and BSW in 0 psu solution, no sperm motility was observed, whereas in 10 psu solution, both BFW and BSW sperms showed low motility and short time post sperm activation. However, diluted in 20 and 32 psu solutions, highest motility and long time post sperm activation were observed in BFW and BSW sperm. SAI of BFW and BSW varied in depend on the osmolality regardless of ion kind and it showed the highest value in the similar osmolality of artificial seawater (956 mOsm/kg). Accordingly, even in sperm released from BFW, factors initiating sperm motility are determined by osmolality.