<![CDATA[The thyroxin hormone plays an important role in the process of metabolism, yolk sac absorbsion, and growth of fish. The aims of this research were to observe the effect of various concentration of thyroxin (T4) on the absolute growth weight, total length, survival rate, and pigment development of pink zebra fish larvae (Brachydanio reiro ) after being reared 42 days. The pink zebra fish larvae at 4 day age with the average weight of 0,002 – 0,003g and average length of ± 3.10 – 3.43 mm were immersed at various concentration of T4 for 24 hours. Prior the treatment fish larvae were dipped into 1 ppt salinity for 2 minutes then transferred into 1 Liter, 1ppt saline and various T4 in plastic bags. The thyroxin concentrations were A (0 mg / L); B (0.05 mg / L); C (0.10 mg / L) and D (0.15 mg / L) respectively. The stocking density was 40 fish/L. After that they were transferred into aquariums and reared for 42 days. Completely Randomized Design (RAL) with four treatments and three replications were used. The variables observed were absolute and specific growth, total length, survival rate and hue degree. The results showed that the thyroxin hormone had significant effect on absolute growth weight, total length and specific growth rate. The dosage 0.1 mg/L was the best treatment on absolute growth, total length, and specific growth rate. Whilee the survival rate showed no significant differences across the treatments. Treatment C also demonstrated the best ppigment development (14.60 + 0.36º hue) compared to others.]]>
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