Abstract:Based on the sample data of Ommastrephes bartramii in 2007 (high yield year) and 2009 (low yield year) collected by Chinese squid fishing fleets, the catch composition and growth rate of Ommastrephes bartramii from July to October between 2007 and 2009 were compared. The results indicated that the mantle length (ML) ranged from 200 mm to 440 mm in 2007, and the dominant ML is 240-310 mm, accounting for 75.41% of the total. The weight range from 280 g to 2 540 g, and the dominant weight is 400-790 g, accounting for 63.11%. While in 2009 the range of ML in catch is 160-430 mm, and the dominant ML is 220-280 mm, occupying 66.87% of the total. The weight range is 43-9 310 g and the dominant weight is 300-510 g, occupying 53.75% of the total. This study found that the catch groups exist in two cohorts, namely, a large group (L-type group) and small groups (S-type group) from July to October in 2007 and 2009. In 2007 the S type group appeared in mid September, accounting for 32.6% of the total. But in 2009 the S type group is ahead of schedule in early September, accounting for 16.2% of the total. The growth rate of L group in 2007 is slightly less than that in 2009, and the growth rate of S type group in 2007 was significantly faster than that in 2009. In this study, combined with marine environmental factors such as sea surface temperature, the cause of difference on catch composition and growth rate between 2007 and 2009 are analyzed and discussed.