Biology analysis of Saurida tumbil in northern South China Sea

Saurida tumbil (Bloch et Schenider) belongs to Myctophiformes, Synodidae, mainly distributed in the India Ocean, the west Pacific and the Yellow Sea and south China Sea. In South China Sea the highest production once reached 18 000 t. Since 1960s', this species has been one of the main captured fish in South China Sea. Some reports on its resource and morphology have been published. But different analysis method and shortage on basic investigating data made some results have errors and subjectivity. In this experiment, growth parameters of Saurida tumbil in northern South China Sea were estimated using ELEFAN technology and the biology data collected from 1960s to 1990s. The results showed that the growth parameters of Von Bertalanffy growth equation was L_∞=58.5 cm,K=0.30,t_0 =-0.39; Natural Mortality Coefficient (M ) was (0.61) from Pauly equation according to growth parameters and average water temperature; Total Mortality Coefficient (Z ) was got from length-converted catch curve with biology datum in different era. The Fishing Mortality Coefficient (F ) in 1980s was calculated that F equaled to 1.55, which increased twice times compared with that in 1960s, and F in 1990s increased twice times compared with that in 1980s, indicating the yield spots nowadays have been in outsides of the optimum yield region. According to the isogram of catch, the stock resource of Saurida tumbil can't be exploited until the body length at first capture (L_ c)reaches to 13.5 cm and F to 3.65. Taking into account the character of sex mature, possible fishing effort and economic requirement, it's suggested that L _c should be decreased from 22.0 cm to 13.5 cm and great efforts in reducing fishing intensity should be made by the government.