Not AvailableVitamin D3 (0.0 IU.100 g body weight (BW)-l.day-l, 100 IU.100 g BW-l.day-l, 500 IU.100 g BW-l.day-l and 1000 IU.100 g BW-l.day-l) was administered intra-peritoneally (ip) to the freshwater threatened Bronze Featherback, Notopterus notopterus kept in freshwater for 9 days. Analyses of serum calcium levels were performed at 0, 6 hr. and 1, 2, 3, 5 and 9 days (four grow-out Notopterus notopterus from each group of ip doses at each interval). Administration of vitamin D3 elevated the maximum serum calcium elevation occurred at day 2 freshwater in 500 IU.100 g BW-l.day-l (11.2±0.92 mg.dL-l) and in 1000 IU.100 g BW-l.day-l (12.0±0.46 mg.dL-l) of the fish maintained in the fresh water. There was gradual decrease in calcium levels from day 3 and became normocalcemia on day 9. Out of the three concentrations of ip Vitamin D3 (100 IU.100 g BW-l.day-l, 500 IU.100 g BW-l.day-l and 1000 IU.100 g BW-l.day-l) the sharp elevation of serum calcium recorded in both 500 IU.100 g BW-l.day-l and 1000 IU.100 g BW-l.day-l. The control (0.0 IU.100 g BW-l.day-l) fish serum calcium behaves like normocalcemia (8.25±0.21 mg.dL-l) in every sampling up to day 2. Results demonstrated that ip Vitamin D3 exerted a dose-dependent and pronounced hypercalcemic effect in freshwater threatened Bronze Featherback, Notopterus notopterus.Not Availabl