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Vertical distributions of large ontogenetically migrating copepods in the Oyashio region during their growing season |
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| Authors: | Atsushi Tsuda Hiroaki Saito Hiromi Kasai |
| Institution: | 1. Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan 2. Tohoku National Fisheries Research Institute, Fisheries Research Agency, Shiogama, Miyagi, 985-0001, Japan 3. Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Kushiro, Hokkaido, 085-0802, Japan |
| Abstract: | Neocalanus flemingeri, Neocalanus plumchrus, Neocalanus cristatus and Eucalanus bungii are large and dominant mesozooplankton occurring throughout the subarctic Pacific. They are an important trophic link and transporter of organic matter to the mesopelagic zone. Vertical distributions of these copepods were investigated from March to October 2000 in the Oyashio region of the western subarctic Pacific. Neocalanus plumchrus and N. flemingeri were distributed in the surface layer (0–50 m) and N. cristatus and E. bungii in the subsurface layer (50–100 m). However, when examined in detail, clear seasonal and vertical differences were observed. Neocalanus plumchrus was concentrated in the top 20 m from late April to the end of July, and N. flemingeri showed a little deeper distribution from May to July. Neocalanus cristatus showed a deeper distribution than that of grazing individuals of E. bungii from April to early July, but grazing individuals of E. bungii (C3–C6) showed a deeper distribution than that of N. cristatus from the end of July to October. Early copepodites of E. bungii were distributed much shallower than late copepodite stages and overlapped with copepodites of N. plumchrus and N. flemingeri. These results suggest that the four species of large copepods have established habitat segregation by season, vertical distribution and food resource partitioning in the Oyashio region as well as other regions of the North Pacific. |
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