Larval fish assemblages in the Kuroshio waters east of Taiwan during two distinct monsoon seasons

Abstract

We investigated changes in the assemblages of fish larvae during two distinct seasons (winter northeasterly monsoon vs summer southwesterly monsoon, 2004) and evaluated their relationships with the hydrographic conditions of the waters off eastern Taiwan. In total, we examined 2326 fish larvae belonging to 78 families, 77 genera, and 223 taxa. Oceanic larvae constituted 67.0% of the total catch and neritic species were 30.3% of the total fish larvae. The catch was dominated by five families: Scombridae (25.5%), Myctophidae (21.1%), Engraulidae (12.6%), Gonostomatidae (5.8%), and Trichiuridae (3.8%). The seasonal difference in total larval fish abundance was not significant; however, abundance of fish larvae was significantly higher in the East China Sea (ECS) shelf break area (transect I) than in transects to the east of Taiwan (II-V). Two seasonal station groups and four assemblages of fish larvae were distinguished. The distribution of fish larvae east of Taiwan was related to the prevailing oceanographic processes at the time of sampling. The dynamic front between the ECS shelf waters and the Kuroshio waters, driven by seasonal monsoons, may be important for the transport of fish larvae. In addition, winter frontal turbulence and upwelling contributed to increased biological production; the development of high chlorophyll a concentrations and zooplankton biomass provided abundant food for the survival of fish larvae.