Maturity and spawning of the giant Pacific octopus, Octopus dofleini was investigated based on the samples collected in the coast of Gangwondo, East Sea, from January to December in 2009. Individuals of mature stage had a higher occurrence rate from February toMay, and gonadosomatic index (GSI) also showed a higher value from February toMay than the other months. For that reason, the spawning period was estimated from February to May with the main spawning period from March to May. The total number of eggs in the fecundity (F) ranged from 9,045 in 11.0 kg (TW) to 148,682 in 16.5 kg (TW), which was proportional to total weight (TW), and the relationship between total weight and fecundity was F=0.185×TW2.238 (R2=0.389). The total weight at 50% group maturity (TW0.5) of female was estimated to be 12.2 kg.

• 이성일(국립수산과학원) | Sung Il LEE (National Fisheries Research and Development Institute, Busan 619-705, Korea)
• 양재형(국립수산과학원) | Jae Hyeong YANG (National Fisheries Research and Development Institute, Busan 619-705, Korea) Corresponding author
• 이해원(국립수산과학원) | HaeWon LEE (National Fisheries Research and Development Institute, Busan 619-705, Korea)
• 김종빈(국립수산과학원) | Jong Bin KIM (National Fisheries Research and Development Institute, Busan 619-705, Korea)
• 차형기(국립수산과학원) | Hyung Kee CHA (National Fisheries Research and Development Institute, Busan 619-705, Korea)