The abundance distribution of mysids (Mysidacea) in the East China Sea

Based on the data of four seasonal investigations in the East China Sea(23°30′-33°00′N,118°30′-128°00′E)from 1997 to 2000,the distribution of mysid abundance,its seasonal changes and dynamics,and relationship with fishing ground were discussed in this paper through qualitative and quantitative methods.Results showed that the total abundance of mysids peaked in autumn with average value,10 ind·10~(-2)m~(-3),and it was the second highest value,5 ind·10~(-2)m~(-3) in spring and the lowest,1 ind·10~(-2)m~(-3) in summer.Since Gastrosaccus pelagicus in spring,Pseudanchialina pusilla in summer and Doxomysis quadrispinosa in autumn and Acanthomysis sinensis in winter contributed more to the total abundance than the other species in each season,with values 0.84,0.39,0.91 and 0.63,respectively,they were the dominant species in the seasons above mentioned.Moreover,the contributions among various dominant species to total abundance of mysids were similar in winter and summer whereas different in spring and autumn.It was found that the total abundance in spring and overall seasons showed significant linear correlation with bottom temperature,while the abundance show significant correlation with bottom salinity in summer and winter,and with surface and 10 m temperature in autumn.The variation of mysid abundance was linked with ebb and flow of runoff from continental rivers,especially affected by the Changjiang Dilute Water.The peak abundance in autumn also associated with the duration of warm current from summer to autumn.The occurence of high abundance area of mysids in autumn plays an important role in forming of fishing ground for Scomber japonicus and Decapterus maruadsi in the north offshore of the East China Sea and the Minnan-Taiwan bank.