The effect of thyroxine on percentage of hatching (Hypophthalmichthys molitrix)

Studies showed that Thyroxine can play an important role on fish growth, osmoregulation system, and other physiological activities. Since the direct effect of thyroxine on growth and metamorphose of bony fish larvae has not been yet approved, therefore, present study were carried out in Shahid Ansary propagation and cultivation farm in order to find out the way of effect of this hormone on the survirval rate and early growth stage of silver carp (Hypophthalmichthys molitrix) fertiled eggs that were bathed in thyroxin with concentrations of 0.1, 0.5 and 1.0 ppm (each one, replicates) for 6 hours. Then they were transfered into large incubators (zoog) with running water. After hatching all larvae were placed in mentioned thyroxin concentration bath for another 6 hours before being transfered into large incubators. Larvae stayed inzoogs until the yolk-sac was absorbed. Finally, live silver carp larvae were counted in separated plates. Results of present study indicated that the ra tio of hatched eggs in 0.5 ppm of thyroxin concentration was higher than other treatment