Improvement in recruitment of Japanese sardine with delays of the spring phytoplankton bloom in the Sea of Japan |
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| Authors: | Taketoshi Kodama Taku Wagawa Seiji Ohshimo Haruyuki Morimoto Naoki Iguchi Ken‐Ichi Fukudome Tsuneo Goto Motomitsu Takahashi Tohya Yasuda |
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| Affiliation: | 1. Japan Sea National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Niigata, Japan;2. National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency, Shizuoka, Japan;3. Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Nagasaki, Japan |
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| Abstract: | To evaluate the impact of temporal variation of primary productivity on the recruitment of Japanese sardine (Sardinops melanostictus) in the Sea of Japan, the phenology of sea surface phytoplankton abundance was estimated from 8 day multiple satellite (SeaWiFS, MODIS‐Aqua, MERIS, and VIIRS) derived sea surface chlorophyll (SSChl) a concentrations from January 1998 to December 2015. Because relationships between SSChl a and in situ chlorophyll a concentrations were significantly different among periods based on the satellite combinations used, maximum and minimum SSChl a concentrations of 1 year were relativized as 1 and 0, respectively. Spatio‐temporal variation of relativized SSChl a concentrations was determined by using empirical orthogonal function (EOF) analysis. Scores in the first EOF mode denoted the basin‐scale variations of SSChl a concentrations in the Sea of Japan, and the major peak from the end of February to the end of May displayed the spring bloom. The logarithm of recruitment per spawner (LNRPS) for sardine was positively affected by delays in the start and end dates of the spring phytoplankton bloom. The delay of the date of the lowest sea surface temperature contributed to the delay of the end of the spring bloom during the period 1998–2015 and elevated the LNRPS during the period 1982–2015. Sardine spawns in the southern Sea of Japan from April to May, hence, delays of the spring bloom prolonged its overlap with sardine larval periods, and thus improved the recruitment of Japanese sardine in the Sea of Japan. |
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| Keywords: | chlorophyll a empirical orthogonal function analysis Japanese sardine ocean color phytoplankton bloom satellites spring bloom |
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