Growth variability of Pacific saury Cololabis saira larvae under contrasting environments across the Kuroshio axis: survival potential of minority versus majority |
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Authors: | Akinori Takasuka Kirara Nishikawa Hiroshi Kuroda Takeshi Okunishi Yugo Shimizu Hideo Sakaji Shin‐Ichi Ito Tadashi Tokai Yoshioki Oozeki |
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Affiliation: | 1. National Research Institute of Fisheries Science, Fisheries Research Agency, Kanazawa, Yokohama, Kanagawa 236‐8648, Japan;2. National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Shimizu, Shizuoka, Shizuoka 424‐8633, Japan;3. Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Kushiro, Japan;4. Tohoku National Fisheries Research Institute, Fisheries Research Agency, Shiogama, Miyagi 985‐0001, Japan;5. National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Hatsukaichi, Hiroshima 739‐0452, Japan;6. Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan;7. Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato, Tokyo 108‐8477, Japan;8. Headquarters, Fisheries Research Agency, Nishi, Yokohama, Kanagawa 220‐6115, Japan |
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Abstract: | Growth variability was examined for Pacific saury Cololabis saira larvae under contrasting environments across the Kuroshio axis, based on samples collected during the winter spawning season in 2013 and 2014. The growth rate index (residual of the otolith marginal 3‐day mean increment width from the linear regression on knob length) of larvae was compared among three areas: the inshore side of the Kuroshio axis, the Kuroshio axis, and the offshore side of the Kuroshio axis in relation to sea surface temperature (SST), salinity (SSS) and chlorophyll‐a (CHL) concentration. The larvae were more densely distributed in the Kuroshio axis and offshore areas of higher temperature and salinity and lower chlorophyll‐a concentration than in the inshore areas of lower temperature and salinity and higher chlorophyll‐a concentration. No marked differences in the growth rate index were found among the three areas, even though the larvae in the inshore areas showed slightly higher growth rates in 2013. Despite the broad ranges of environmental factors, no clear relationship between the growth rate index and any environmental factor was detected. The survival potential of Pacific saury larvae was considered to be at least comparable under contrasting environments across the Kuroshio axis. Such a geographical homogeneity is concluded to be attributable to compensable effects of physical and biological factors. We hypothesize that the minority under physically‐unfavorable but biologically‐favorable conditions on the inshore side of the Kuroshio axis could survive equally well as the majority under physically‐favorable but biologically‐unfavorable conditions around the Kuroshio axis and on the offshore side of the Kuroshio axis. |
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Keywords: | Chlorophyll environmental factor growth rate Kuroshio axis larvae otolith Pacific saury salinity survival temperature |
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