Winter assemblages of ichthyoplankton in the waters of the East China Sea Shelf and surrounding Taiwan

The relationships between larval fish assemblages and hydrographic features in the East China Sea (ECS) and waters surrounding Taiwan were studied in the winter of 2008. A total of 3824 larvae representing 165 taxa in 82 families were identified. Sigmops gracilis was the most dominant species, accounting for 19.15 % of the total larval fish samples, followed by Scorpaenidae spp. (5.88 %) and Valamugil sp. (5.70 %). Through a cluster analysis, the spatial distributions of larval fishes were classified into four assemblages: Kuroshio subassemblage I, Kuroshio subassemblage II, ECS assemblage, and Taiwan Strait (TS) assemblage. During the winter, high abundance of larval fishes was observed in the warm offshore Kuroshio areas, whereas low abundance was observed in the ECS region. The environment of Kuroshio was suitable for the survival of mesopelagic fish larvae, among which the most dominant species was S. gracilis. Demersal fish larvae thrived in the ECS and TS, where Scorpaenidae spp. larvae were the dominant taxa. In addition, water masses north of Taiwan were located in a conflux zone comprising the Mixed China Coastal Water (MCCW) and the Kuroshio Current. Moreover, a frontal zone also formed between the northward intrusion of Kuroshio Branch Water and MCCW in the middle of the TS. Consequently, the structures of larval fish assemblages exhibited transitional features in these frontal areas. The geographic locations and distribution patterns of larval fish assemblages in the study area corresponded closely with the hydrographic conditions during the northeastern monsoon.