Biological characteristics and stock changes of Loligo edulis in Beibu Gulf, South China Sea

Based on the data collected from Beibu Gulf, South China Sea in four seasons of 2007, the biological characteristics and stock changes of Loligo eduliswere analyzed. The results show that individuals at the biggest mantle length and body weight as well as the dominant mantle length and body weight groups of L.edulis occurred in autumn. Female squids outnumber males significantly and mature stageⅡ dominats the population. The smallest mantle length for sex-differentiation and sexual maturation are 56 mm and 67 mm, respectively. The feeding intensity (grade 1) is low and larval swordtip squids are found throughout the year. Compared with the results of 1997~1999 and 2000~2002, the seasonal changes of the catch rate are evident. The occurrence rate and average catch rate of L.edulis in 2007 increase compared withthe dataof 1997~1999, while decrease compared with that of 2000~2002. The results indicate that the stock of L.edulis in Beibu Gulf fluctuates rather greatly and should be appropriately used and protected.