Annual variability of ichthyoplankton in the Yangtze River estuary of China from August 2002 to 2009

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Abstract The annual variability of ichthyoplankton in the Yangtze River estuary, located at the junction of the East China Sea and the Yellow Sea, on the continental shelf at the western rim of the Pacific Ocean, was studied using vertical tows at twenty stations from August 2002 to August 2009. Basic oceanographic parameters such as temperature and salinity were also measured to evaluate their relationship to the abundance of ichthyoplankton. The eggs or larvae of a total of 34 fish species were present in the samples. Only 8 species were found to occur during every year. Engraulis japonicus and Stolephorus commersonii eggs, as well as Coilia mystus and Stolephorus commersonii larvae, were highly abundant during this period. Additionally, water storage in the Three Gorges Reservoir, which began in June 2003, had significant effects on the abundance of estuarine species, as well as on the composition and diversity of ichthyoplankton; this became evident when these values were compared to the findings from 2002. The number of species (species richness) and abundance of each species varied among the stations relative to the salinity in the estuary during the study period.