Spatial distribution of early life stages of anchovy (Engraulis japonicus) and hairtail (Trichiurus lepturus) and their relationship with oceanographic features of the East China Sea during the 1997–1998 El Niño Event

The spatial distribution of early life stages of anchovy (Engraulis japonicus) and hairtail (Trichiurus lepturus) and their relationship with oceanographic features of the northern East China Sea (32°N, 124°E to 33°N, 128°E) has been investigated using ichthyoplankton surveys and oceanographic observations during May and August 1997–1998. Geographical distribution patterns and relationships with temperature, salinity, chlorophyll a, and zooplankton abundance indicated that the anchovy population was mainly spawning in the East China Sea shelf water influenced by the Yangtze River, while the hairtail population was spawning in the warm Kuroshio Current and the zone in which it mixed with the East China Sea shelf water. The El Niño Southern Oscillation (ENSO) index increased in the summer of 1997 and decreased in the summer of 1998, with two peaks in August 1997 and March 1998. High densities of anchovy eggs and larvae were observed in areas of low salinity following heavy rains around the Yangtze River in May and August 1998 (after El Niño). This suggested that the mechanism of ENSOʹs connections is through the influence of water from the Yangtze River which can affect the productivity in the spawning grounds and the extension of nursery grounds eastward into the East China Sea.