Physical researchers note that the Kuroshio moves onshore both in the nutrient-poor surface layer and in the nutrient-rich subsurface layer (Lee and Matsuno, 2007) and there are abundant nutrients during winter south of the main axis of the YSWC (Changjiang River estuary) (Chen, 2009; Wang et al., 2003). Therefore, there is another possible explanation in that the warm and nutrient- rich water might partially originate from the subsurface nutrient-rich water of the Kuroshio and/or from the Changjiang (Yangtze) River estuary.