THE EFFECT OF THYROXINE ON THE GROWTH AND YOLK RESORPTION OF CHUM SALMON (ONCORHYNCHUS-KETA) YOLK-SAC LARVAE

Effects of immersion treatment of Na-L-thyroxine (T-4) On chum salmon, Oncorhynchus keta, yolk-sac larvae were studied. Treatment experiment s were carried out with various combinations of T-4 concentration and treatment duration (0.1 ppm-60 min; 0.5 ppm-30 min, 60 min; 1.0 ppm-60 min) for 18 days, from 15 to 33 days after hatching. The T-4 treatmen t caused a significant increase in the growth rate of the larvae. Trea tment with thyroxine at 0.5 ppm for 60 min resulted in the most signif icant increase in total length and total weight. This treatment accele rated yolk-sac resorption and caused thickening of the epidermis.