支柱式ノリ養殖施設によるアサリ稚貝の定着促進効果

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To identify the effects of horizontal spreading of macro-algal culture (Nori Porphyra yessoensis) nets on promoting colonization of juveniles of Asari clam Ruditapes philippinarum at intertidal sandy bottom, seasonal changes in density of clams and sea water flow were monitored at the field plots which established in the tidal flat in Ise Bay, Japan, during 2007. There was no significant difference of densities of juvenile clams between plots during the period of spat-recruitment in summer (nets were not spread). However, in the experimental plot (nets were spread at +50cm higher than the bottom surface), spatial densities of new settlers (shell length<0.3mm) and small bivalves (shell length 0.3-1.0mm) were observed denser than in the control plot (nets were not spread), during the period of spat-recruitment in autumn. The current velocity, which was measured at +10cm above the bottom surface, decreased after nets were spread in the experimental plot. Both in the experimental plots and in the control plot ones, whereas the shear stress of currents was lower than the calculated critical tractive force for the sediment grains and the new settlers throughout the experiment, shear stress of waves sporadically exceeded the critical tractive force. Consequently, movement of the new settlers may be influenced by the sea water current when the shear stress of waves exceeded the critical tractive force. We concluded that the reduction of the current velocity by the horizontally spread Nori-culture nets may have facilitated to trap the settled juveniles of Asari clam under the net at the experimental plot in Ise Bay.
日本水産工学会の論文
2012-11-15

支柱式ノリ養殖施設によるアサリ稚貝の定着促進効果

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