Experiments on the acclimatisation of salt water fish seed to freshwater

Summary

• 1. Laboratory and field experiments, carried out during 1945—48 on the acclimatisation of fry and early fingerlings of mullets (Mugil cephalus,M. sehelii, etc.),Megalops cyprinoides andElops saurus (leptocephalus and later stages),Gerres filamentosus, Scatophagus argus, Sillago. sihama,Hemirhampus gaimardi andAmbassis sp. are described.

• 2. An attempt has been made to elucidate the physico-chemical variables in the medium during the several stages of transition of the young fish from salt water to freshwater.

• 3. In the early post-larval stage, most of the above fishes possess the capacity for quick adaptation to wide and sudden fluctuations in salinity and other environmental conditions; but advanced stages (2 to 3 inches long) of atleastMegalops andElops are found to be more susceptible to such changes, resulting in considerable mortality.

• 4. The knowledge that these common food fishes, at this early stage, can withstand even direct transfer from brackish water to freshwater has a bearing on the possibilities of their successful culture in freshwater. Their small size and low mortality during acclimatisation would enable transport of large numbers at relatively low cost.