Estimation of spawning sites in the spotted flagtail, Kuhlia marginata, based on sperm motility

To estimate the spawning site of the spotted flagtail, Kuhlia marginata, sp erm motility was examined under conditions of different salinities. The spe rmatozoa were immotile in 0 and 5 ppt test solutions and in seminal fluid b ut lived longer in 20-30 ppt. Sperm were most active at 25-35 ppt. Therefor e, we considered that spotted flagtail spawn in 20-35 ppt salinity. Because the mean salinity of the Genka estuary is below the optimum required for s pawning, the spawning site in Okinawa Island would be seawater. This eviden ce suggested that the spotted flagtail is a catadromous species.