Abstract: Based on the data of stow net survey in Southern Yellow Sea (SYS) from November 2008 to September 2009, this paper studied the population structure and reproductive biology of   Todarodes pacificus in the area, through the evaluation of the seasonal patterns in size structure, sex ratio (r_sex), mantle length (L_M) at first maturity, and relationships between L_M and body weight. The individuals of T. pacificus were distributed in SYS all year round. In autumn and winter, T. pacificus population was mainly consisted of mature individuals, while in spring and summer, the population was mainly consisted of immature individuals. The number of females was significantly higher than that of males, with the total r_sex being 0.60. When the L_M ranged from 190-280 mm, the relationship between r_sex and L_M could be expressed as r_sex=3×10^-5L_M^1.8017. The maturity stage tended to be increased with L_M. The monthly variation of the mean value of gonado-somatic index (GSI) for T. pacificus males and females was evident. The GSI approached the peak in autumn and winter, suggesting that the spawning of T. pacificus was mainly in autumn and winter. Both the GSI and the maturity stages (except Ⅴstage) were positively related to L_M. The L_M at first maturity for females and males was 201.9 mm and 174.3 mm, respectively. The relationship between L_M and body weight differed from maturity stages. At the late development stage of T. pacificus, the increase in body weight was mainly due to gonad maturation rather than somatic growth.

Key words: Rice, Volatile infochemicals, Characteristic and function, Pest control