Migration of freshwater fish in mangrove swamp of Singapore

Summary

The limnological survey of Sungai Kranji, a river in mangrove swamps in the northern part of Singapore, was carried out in the year of 1983. The salinity of the water near the mouth of the river varied between 19.5 and 24.0‰ and the pH between 7.8 and 8.0. The fish, Oryzias javanicus, was collected from the river. The tolerance of the adult fish and fry to salinities, ranging from 0 to 100% sea water was studied. Adults were more tolerant to different salinities than the fry. The optimal salinity for survival of adults and dry seemed to correspond to 30–50% sea water. The spawning habit of the fish in 50% sea water was observed. Spawning and non-spawning periods alternated in weekly cycles with daily spawning during the spawning period.