A preliminary study on biological characteristics of Auxis thazard in the South China Sea

We investigated the biological characteristics of Auxis thazard collected from light-falling net fishery in the South China Sea in spring and autumn of 2014. The results show that the dominant fork length ranged from240 to 300 mmin spring while from220 to 260 mmin autumn, accounting for 60.3% and 77.8% of the total number, respectively. The relationship between fork length and body weight had little difference in spring and autumn. Significant difference was not found in total sex ratio in spring and autumn ( P 0.05) , but was found in fork length groups in spring and autumn ( P 0.001) . StageⅡ had the maximummaturity in spring. The proportion of mature females decreased and mature males increased with increasing fork length. With the development of gonad, the average GSI values increased at different gonadal stages and females had higher GSI values than males. The fork length of the first gonadal maturity was 304. 5 mm. Stage 0 and Stage 1 had the highest feeding intensity, accounting for 43.1% and 43.4% of the total number, respectively.