Abundance distribution of Euphausiids in the East China Sea

Based on the data of four seasonal investigations in the East China Sea (23°30′-33°N, 118°30′-128°E)from 1997 to 2000, the distribution and the seasonal changes of Euphausiids abundance and the relation between its abundance dynamics and fish ground were discussed in this paper through qualitative and quantitative methods. Results showed that the total abundance of Euphausiids peaked in autumn, and declined to the lowest in winter. The abundance in spring was the second highest in four seasons. Since Euphausia nana in winter, spring, summer and Pseudeuphausia sinica in autumn contributed more to the total abundance, they actually dominated the variations of the total abundance. Moreover, it was found that the total abundance in summer showed linear correlation with bottom water temperature and 10m salinity, while the abundance in other three seasons did not show significant correlation with hydrographic factors. High abundance area of Euphausiids was located in the converging area of Taiwan warm current and other water masses in autumn, suggesting that the variation of the total abundance was dependent on water masses and the dominant species. The latter was also related to their ecological features. It was also found that the high abundance area nearly overlapped the grazing areas of some economic fishes such as Trichiurus lepturus, Scomber japonicus and Larimichthys polyactis.