FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

Black porgy, Acanthopagrus schlegeli, is one of the most important aquaculture species in Taiwan. It is a euryhaline species, but its reproduction only occurs in marine environments. That is, lower salinities do not hamper the survival of black porgy, but seriously interfere with its reproduction. The aim of this study was to investigate the influence of salinity conditions on the final maturation of gonads in black porgy. The experiment was carried out in the natural spawning season of black porgy, i.e., from January to March. The fish, caught from our field ponds, were acclimated to 5 salinities of 5, 15, 25, 35, and 45 ppt, for at least 2 mo. The results showed that acclimation salinity did not influence the size of oocyte diameter in female porgy. However, the female black porgy which was placed in 35 and 45 ppt had higher ovulation rates and longer ovulation times than did ones in lower salinities. The acclimation salinity did not result in different spermatocrit values of male black porgy, but it did influence sperm motility. Sperm of fish incubated in 35 ppt had significantly higher motility activity and longer motility time than did ones in < 15 and 45 ppt. Based on these results, the study suggested that in order to promote fertilization rates, black porgy during final maturation should be reared in a salinity of around 35 ppt.