Bull. Jpn. Soc. Fish. Oceanogr. 81(1), Page 36-42, 2017   Age and growth of spear squid (Heterololigo bleekeri) caught in the coastal water off Miyagi Prefecture Yoshio Masuda1†*, Keiichi Onodera1 and Satoshi Katayama2 1 Miyagi Prefecture Fisheries Technology Institute, Ishinomaki, Miyagi 986-2135, Japan * Present address: Fishery Industry Promotion Division, Agriculture, Forestry and Fisheries Department, Miyagi Prefecture, Sendai, Miyagi 980-8570, Japan 2 Laboratory of Fisheries Biology and Ecology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, Japan † E-mail: masuda-yo943@pref.miyagi.jp Age and growth of the spear squid, Heterololigo bleekeri, from 288 squids caught in the coastal water off Miyagi Prefecture from July 2014 to June 2015 were examined using a statolith microstructure. The logistic growth equation was well fitted to examine the relationship of age and mantle length. The growth equations were shown as follows, M.L.=312/(1+e4.87−0.0294t) for male and M.L.=225/(1+e4.68−0.0317t) for female, where M.L. is mantle length in mm and t is age in days. A significant difference in growth equations between males and females was detected, which confirmed that males grew bigger than females (F=44.2, p<0.01). The hatching periods of H. bleekeri were estimated to be from February to September, with the main periods being from April to June. Key words: Heterololigo bleekeri, spear squid, statolith microsturucture analysis, growth