Effects of Kuroshio Path Variations on the Growth and Maturation of <I>Gelidium elegans</I> (Gelidiaceae, Rhodophyta) on the Coast of Hachijo-jima Island, Central Japan

  • Komazawa Ichiro
    Hachijo Branch, Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries
  • Takase Tomohiro
    Oshima Branch, Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries
  • Tanaka Yuhei
    Tokyo Metropolitan Ogasawara Fisheries Research Center, Ogasawara-mura
  • Hayakawa Kouichi
    Hachijo Branch, Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries

Bibliographic Information

Other Title
  • 八丈島におけるマクサの生長と成熟におよぼす黒潮流路変動の影響
  • ハチジョウジマ ニ オケル マクサ ノ セイチョウ ト セイジュク ニ オヨボス クロシオ リュウロ ヘンドウ ノ エイキョウ

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Abstract

Seasonal changes in growth and maturation of Gelidium elegans populations and oceanographic conditions around Hachijo-jima Island, central Japan were studied to clarify the relationships between the phenology of G. elegans and the oceanographic conditions by using monthly random samplings from April 2005 to December 2010. Moreover, the relationships between the past standing crop and the seawater temperature during growth periods of G. elegans were analyzed. Frond length and wet weight of G. elegans showed clear seasonality, they started to increase from autumn, attained a maximum in early summer from spring, then decreased from summer to autumn. From the periods when the daily growth rate of wet weight of G. elegans increased, the growth phase in Hachijo-jima Island was from January to May. When the types of Kuroshio path around Hachijo-jima Island affected the coastal side, monthly averaged seawater temperature anomaly showed negative values, and the concentrations of DIN and PO4-P remained at high values. A significantly negative correlation was found between the seawater temperature of growth periods and the standing crop of G. elegans. We conclude that high water temperature during the growth period of G. elegans might not have affected the recent decrease of G. elegans, the main factor causing the decrease might have been the low nutrient concentration around Hachijo-jima Island.

Journal

  • Aquaculture Science

    Aquaculture Science 60 (2), 169-177, 2012

    Japanese Society for Aquaculture Science

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