Zoological Studies

Vol. 55, 2016

(update: 2016.9.19)

Succession of monsoons and water mass influences on euphausiid assemblages in the waters around Taiwan, western North Pacific Ocean

Ren-Jye Hsieh1, Hung-Yen Hsieh2,3, and Wen-Tseng Lo1,*

1Institute of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
2Graduate Institute of Marine Biology, National Dong Hwa University, Checheng, Pingtung, Taiwan
3National Museum of Marine Biology and Aquarium, Checheng, Pingtung, Taiwan

(Received 17 April 2016; Accepted 22 August 2016)

Ren-Jye Hsieh, Hung-Yen Hsieh, and Wen-Tseng Lo (2016) This study took advantage of the zooplankton samples collected by the Fisheries Research Institute that implemented Taiwan Cooperative Oceanic Fisheries Investigation, the first large scale hydrographic and plankton survey around Taiwan Island. The aim of the study was to elucidate the spatial and temporal distribution patterns of euphausiids and their correlations with the hydrographic features during the southwesterly (summer) and northeasterly (winter) monsoons in 2004. A total of 35 taxa of euphausiids belonging to 6 genera and 1 family were recognized from our studied samples. The five predominant species were Pseudeuphausia lalifrons, Stylocheiron sp., Stylocheiron suhmii, Euphausia pacifica and Stylocheiron carinatum, together comprising 54.6% of the total euphausiid catch. Abundance, species richness and species diversity of euphausiids were significantly higher in summer than in winter. Cluster analysis revealed two station groups during both seasons. Higher abundance and lower species richness generally were observed in waters west of Taiwan where the China Coastal Current prevails, and a reverse condition was found in the waters east of Taiwan where the Kuroshio Current dominates. The distribution patterns in abundance and species assemblages were closely correlated with the hydrographic conditions, and well linked with the abundance of zooplankton and chlorophyll a concentration. Euphausiid assemblage showed clear seasonal variations. The succession of water mass induced by monsoon apparently affects the distribution patterns of euphausiids in the study area.

Key words: Euphausiid; Distribution; Monsoon; Water mass; Taiwan.

*Corresponding authors. E-mail: lowen@faculty.nsysu.edu.tw; hyhsieh@mail.ndhu.edu.tw

Vol. 55, 2016