Todarodes pacificus using data collected from bottom trawl surveys in the East China Sea during the summers between 2009 and 2012. We estimated the resource density, sex ratio, size structure, and the relationship between mantle length and body weight and mantle length at first maturity in each year. individuals were common but unevenly distributed. The population density was highest in 2009 and lowest in 2010. There was no difference (>0.05) in the abundance of males and females, with the total sex ratio being 1T. pacificus consisted primarily of immature individuals and the dominant mantle length was less than 200 mm. The dominant mantle length was highest in 2012 and lowest in 2011. The relationship between mantle length and body weight was quantified as an exponential growth curve, and there were significant differences among years (<0.05). The stage of maturity increased with mantle length increasing. The mantle length at first maturity in females was larger than in males. In summary, the population of during the summer fishing season consisted primarily of immature individuals from the autumn and winter spawning groups, with a low number of small mature individuals from the summer spawning group. We observed intra annual differences in the rate of growth and development and the population structure. Our results provide a theoretical basis for managing the fishery in the East China Sea during the summer fishing season.