Title Reduction of Eisenia bicyclis bed by a grazer Strongylocentrotus nudus off Oshika Peninsula: as an example of urchin barren in northeastern coast of Honsu, Japan
Authers Daisuke MURAOKA
Keywords grazing, Eisenia bicyclis, sea urchins, Strongylocentrotus nudus, degeneration, kelp beds, monitoring
Citation Bull. Fish. Res. Agen. No.32, 75-82, 2010
The reduction of seaweed beds (Isoyake) has been known nearly all over the country in Japan. In northern Japan, reduction of kelp beds has significant consequences on the local fishing community dependent on the kelp and herbivores such as sea urchins and abalone. Hearing to prefectural governments by Fisheris Agency has shown that the major factor causing the reduction of kelp beds in northern Japan is sea urchin grazing. As an example of a receding kelp bed in the cold temperate waters , I show the results of a local ecological survey of Eisenia bicyclis bed and the sea urchin (Strongylocentrotus nudus) and abalone (Haliotis discus hannai ) on the rocky coastal area in Tomarihama of Oshika Peninsula, Miyagi Prefecture (northern Japan). This survey indicated that the high grazing pressure of sea urchins reduced the survival of juvenile E. bicyclis sporophytes near the lower limit of the bed, thus impeding the recruitment of juvenile in the area formerly occupied by adult sporophytes.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull32/75-82.pdf