Oceanographic factors affecting interannual recruitment variability of Pacific saury (Cololabis saira) in the central and western North Pacific |
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| Authors: | Taro Ichii Haruka Nishikawa Kedarnath Mahapatra Hiroshi Okamura Hiromichi Igarashi Mitsuo Sakai Satoshi Suyama Masayasu Nakagami Miyako Naya Norihisa Usui Yoshihiro Okada |
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| Affiliation: | 1. National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa, Japan;2. Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokohama, Kanagawa, Japan;3. School of Marine Science and Technology, Tokai University, Shizuoka, Japan;4. National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa, Japan;5. Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Hachinohe, Aomori, Japan;6. Japan Fisheries Research and Education Agency, Yokohama, Kanagawa, Japan;7. Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Ibaraki, Japan |
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| Abstract: | Pacific saury (Cololabis saira) has a short life span of 2 years and tends to exhibit marked population fluctuations. To examine the importance of sea surface temperature (SST) and mixed layer depth (MLD) as oceanographic factors for interannual variability of saury recruitment in early life history, we analyzed the relationship between abundance index (survey CPUE (catch per unit of effort)) of age‐1 fish and the oceanographic factors in the spawning and nursery grounds of the previous year when they were born, for the period of 1979–2006, in the central and western North Pacific. Applying the mixture of two linear regression models, the variability in the survey CPUE was positively correlated with previous year's winter SST in the Kuroshio Recirculation region (KR) throughout the survey period except 1994–2002. In contrast, the survey CPUE was positively correlated with the previous year's spring MLD (a proxy of spring chlorophyll a (Chl‐a) concentration) in the Kuroshio‐Oyashio Transition and Kuroshio Extension (TKE) during 1994–2002. This period is characterized by unusually deep spring MLD during 1994–1997 and anomalous climate conditions during 1998–2002. We suggest that saury recruitment variability was generally driven by the winter SST in the KR (winter spawning/nursery ground), or by the spring Chl‐a concentration (a proxy of prey for saury larvae) in the TKE (spring spawning/nursery ground). These oceanographic factors could be potentially useful to predict abundance trends of age‐1 saury in the future if the conditions leading to the switch between SST and MLD as the key input variable are elucidated further. |
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| Keywords: | chlorophyll Kuroshio Kuroshio‐Oyashio Transition mixed layer depth mixture of regression model Pacific saury recruitment temperature |
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