control group 0 05 in the group administered with 1 u03bcg l of pionine and 0 02 in the group administered with 10 u03bcg l of pionine thus the tyrosinase inhibitory activity was observed in the group to which pionine was administered ryukins weighing 3 5 g were fed in a 0 9 nacl aqueous solution for 12 days to induce surface melanism the goldfish were grouped into five fish each in two experiment groups the fish were fed in a water bath for 12 weeks during which pionine was add in an amount of 1 u03bcg l and 10 u03bcg l respectively three times per week in the control group the fish were fed in pure water the recovery from surface melanism of the experiment groups was compared with that of control group the recovery from surface melanism was not observed in all of the groups within the period of three weeks but there appeared to be some difference between the experiment groups and the control group after 6 weeks after 12 weeks the gold fish returned to their original yellow surface color in 0 10 goldfish 0 in the control group 4 10 40 in the 1 u03bcg l pionine administered group and 8 10 80 in the 10 u03bcg l pionine administered group black popeyed goldfish each group 5 fish were fed in a water bath in experimental group pionine was added to the.