Therefore, it is possible to recognize changes in geographical di

Therefore, it is possible to recognize changes in geographical distribution of seaweeds along the coast in the northwestern

Pacific Ocean due to global warming. Most of Sargassum species mature in early spring to early summer around Japan. When they become large around the mature season, some of them have been sometimes detached from the bottom by strong waves ( Yoshida, 1963). Sargassum species can float due to their vesicles after being detached. While some are stranded on the beach, the others are transported to offshore waters by surface currents due to positive buoyancy produced by many vesicles. Floating Sargassum species are called as Nagare-mo floating seaweeds or seaweed selleck compound rafts in Japan ( Yoshida, 1963). Floating seaweeds are commonly found in Japanese waters ( Yoshida, 1963) from spring to early summer, as in the Sargasso Sea. In this particular area, floating

seaweeds spend their entire floating-life stage in a vegetative reproductive state ( Parr, 1939). Floating seaweeds play key ecological roles in Dabrafenib mw offshore waters as well, as they play host to attaching or accompanying flora and fauna (Thiel and Gutow, 2005). Hence, floating seaweeds constitute moving ecosystems (e.g., Cho et al., 2001 and Abé et al., 2012). Thus, they serve as means of dispersal for littoral animals such as intertidal animals (e.g., Ingólfsson, 1995). With regard to fisheries, they are spawning habitats for flying fish (Ichimaru et al., 2006), Japanese halfbeak and Pacific saury (Cololabis saira Brevoort) ( Ikehara, 1986). They also serve as nursery habitats for larvae and juveniles of some commercially important pelagic fish species ( Ikehara, 2006), such as yellowtail

(Seriola quinqueradiata Temminck & Schlegel) ( Yamamoto et al., 2007) or jack mackerel (Trachurus japonicus Temminck & Schlegel) ( Senta, 1965), which spawn in the East China Sea ( Fig. 1). Recent studies suggested that the origin of floating seaweeds in East China Sea consisting of only one species, Sargassum horneri C. Agardh, is Chinese coast, especially off Zhejiang Province ( Komatsu et al., 2005, Komatsu et al., 2013 and Mizuno et al., 2013) because this species is not distributed south of Kyushu Island and Ryukyu Archipelago ( Komatsu et al., Progesterone 2007, Komatsu et al., 2009 and Filippi et al., 2010). Consequently, investigating change in spatial distribution and abundance of floating seaweeds consisting of S. horneri and spawning zones of yellowtail defined as surface water temperatures in this specific area is of primary interest for fishery purposes. S. horneri is one of important seaweed aquaculture species as food in Japan and Korea (Ajisaka, personal communication). Spatial distribution of this species is very wide from Hokkaido Island in a boreal zone to north Kyushu Island facing East China Sea and central Honshu Island facing the Pacific Ocean in a temperate zone.

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