Language：English   Publisher：The Plankton Society of Japan, The Japanese Association of Benthology  

<p>The northern Satsunan area, comprising the mouth of Kagoshima Bay and Osumi Strait, is an important spawning and nursery ground for Japanese jack mackerel <i>Trachurus japonicus</i> in Japan. Upwellings frequently occur at the mouth of the bay during winter and spring, and the consequent nutrient supply promotes phytoplankton blooms. This study examined how <i>T. japonicus</i> utilizes upwelling (Kagoshima Bay) and non-upwelling areas (Osumi Strait) as larval nursery grounds. Densities and growth rates (measured as the average width of the last three otolith increments) of <i>T. japonicus</i> larvae in both areas were compared to determine the upwelling influence on nursery ground formation. The mouth of the bay had lower temperature and salinity but higher chlorophyll-<i>a</i> concentrations and prey density than that of the strait. Densities of larvae were consistently higher in the bay than in the strait, indicating that the main nursery of <i>T. japonicus</i> is formed in Kagoshima Bay. No significant differences were observed in the growth rates of larvae among areas, suggesting that lower temperatures and prey availability are growth limiting factors in the mouth of the bay and the strait, respectively, and the Osumi Strait could also provide a favorable nursery area.</p>

DOI： 10.3800/pbr.18.148

Scopus

Language：Japanese   Publisher：Progress in Oceanography  

Major forage fishes spend their vulnerable early life stages in the Kuroshio and its neighboring waters where phytoplankton standing stocks are much lower than in coastal areas. Nevertheless, little is known of how mesozooplankton and fish larvae with their high biodiversity are supported in the Kuroshio ecosystem. Here we report stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) for mesozooplankton and fish larvae from coastal to pelagic sites in the East China Sea to evaluate trophic sources and pathways at lower trophic levels in planktonic food webs under different environmental regimes. Although δ13C and δ15N in mesozooplankton and fish larvae varied among taxonomic groups and sites, mesozooplankton δ13C and δ15N tended to be lower for particle-feeders than carnivores and fish larvae and at more pelagic sites than in coastal waters. There were significant linear regressions between δ15N and δ13C of mesozooplankton communities, with the similar slopes among sites and lower intercepts at more pelagic sites. The δ15N and δ13C of small copepods, euphausiids, ostracods, appendicularians and fish larvae were aligned close to the regression line covering all regions, indicating that these were trophic sources and pathways to mesozooplankton and fish larvae. Our results suggest that trophic sources of mesozooplankton and fish larvae are supported through copepods and appendicularian-integrated microbial production and are more dependent on diazotrophic production in more pelagic waters.

DOI： 10.1016/j.pocean.2022.102952

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Language：English   Publisher：Journal of Marine Systems  

DOI： 10.1016/j.jmarsys.2022.103767

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Language：English   Publisher：Frontiers in Marine Science  

DOI： 10.3389/fmars.2021.725227

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Language：Japanese   Publisher：Estuarine, Coastal and Shelf Science  

DOI： 10.1016/j.ecss.2021.107472

Scopus