关键词: 西北太平洋公海, 日本鲭, 胃含物, 食性特征, 摄食等级

Abstract: In order to understand the basic biology characteristics and dietary characteristics of  main economic species caught by the Chinese light-purse seine and light lift net fishery, this paper studied the biological characteristics such as sex and feeding level of chub mackerel (Scomber japonicas), based on the biological data of S. japonicas which collected in fishing vessels in Northwest Pacific Ocean high seas from Oct. to Nov. in 2016 and Apr. to Nov. in 2017. The results showed that the diet of S. japonicas in Northwest Pacific Ocean included 9 taxa (such as shrimps, fishes, copepods) and 16 subgroups of prey species. Shrimps were the dominated prey and Euhausiacea sp. was the most dominated one. The weight percentage (W) of fish prey was relatively higher than that of shrimps, however its numeric percentage value (N) was lower than the half value of shrimps. There was more species in the stomach of S. japonicas in summer and autumn than those in winter and spring. But it varied in  different seasons. There was no significant changes in feeding intensity and stomach fullness index (P) of chub mackerel with fork length less than 300 mm or body weight less than 300 g. However the feeding level and stomach fullness index  of chub mackerels tended to increase with their body size or weight in which with the fork length more than 300 mm or the weight more than 300 g. S. japonicas with the fork length more than 300 mm have lower trophic niche than that with the fork length less than 300 mm, because it feed more large bait. This study provided a basic data for the management and sustainable development of chub mackerel resources in the Northwest Pacific.

Key words: high seas in Northwest Pacific, Scomber japonicas, stomach contains, food characteristics, trophic level