On 6th of October, 1933 the author released Mactra sachalinensis of the size, length 8.5cm high 7.1cm with description tag at the shore of Osyamanbe, Yamakoshigun, Hokkaido and recaptured the same at this shore on 10th of February, 1948 with the size of length 11.5cm high 9.2cm.
According to our investigation of the growth of this kind of shell at the year of 1945, the one length 8.5cm can be regarded 12 years old, therefore it can be confirmed that above recaptured shell already has been kept life of 26 years as this one passed 14 years 4 months since released.
