Wind‐induced stock variation of the neon flying squid (Ommastrephes bartramii) winter–spring cohort in the subtropical North Pacific Ocean |
| |
| Authors: | Haruka Nishikawa Takahiro Toyoda Shuhei Masuda Yoichi Ishikawa Yuji Sasaki Hiromichi Igarashi Mitsuo Sakai Masaki Seito Toshiyuki Awaji |
| |
| Affiliation: | 1. Japan Agency for Marine‐Earth Science and Technology, Kanazawa‐ku, Yokohama, Japan;2. Meteorological Research Institute, Japan Meteorological Agency, Nagamine, Tsukuba, Ibaraki, Japan;3. Hachinohe Station, Tohoku National Fisheries Research Institute, Fisheries Research Agency, Same‐machi, Hachinohe, Aomori, Japan;4. Fisheries Research Institute, Aomori prefectural Industrial Technology Research Center, Hiranai‐machi, Higashi Tsugaru‐gun, Aomori, Japan;5. Kyoto University, Sakyo‐ku, Kyoto‐shi, Kyoto, Japan |
| |
| Abstract: | Our examination of the neon flying squid (Ommastrephes bartramii) winter–spring cohort catch per unit effort (CPUE, an index of stock) revealed significant positive correlations with the interannual variations of observed chlorophyll‐a (Chl‐a) concentration and autumn–winter mixed layer depth (MLD) in the winter–spring feeding grounds of paralarvae and juveniles (130–170°E, 20–27°N). These correlations suggest the importance of integrated bottom‐up effects by the autumn–winter MLD for the neon flying squid stocks. However, the influence of autumn–winter MLD interannual variation in the forage availability for paralarvae and juveniles, i.e., particulate organic matter and zooplankton, has still been unclear. In this study, we use the lower trophic ecosystem model NEMURO, which uses the physical environmental data from the ocean reanalysis dataset obtained by the four‐dimensional variational (4DVAR) data assimilation method. The model‐based investigation enables us to clarify how the autumn–winter MLD controls the particulate organic matter and zooplankton abundance in the feeding grounds. Further, our investigation of the autumn–winter MLD interannual variation demonstrates that the stronger autumn wind in the feeding grounds develops a deeper mixed layer. Therefore, the deep mixed layer entrains nutrient‐rich water and enhances photosynthesis, which results in good feeding conditions for paralarvae and juveniles. Our results underline that the wind system interannual variation has critical roles on the winter–spring cohort of the neon flying squid stock. |
| |
| Keywords: | data assimilation ecosystem model mixed layer depth neon flying squid wind system |
|
|
