植食動物の除去による藻場回復の実践,長崎県大瀬戸での取り組み(平成21年度日本水産工学会秋季シンポジウム「持続的な磯焼け対策の実践に向けて」)

概要

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Since 1995, disappearance of seaweed beds so-called Isoyake became conspicuous at Ooseto, west coast of Nishisonogi Peninsula, Nagasaki Prefecture. The local fishermen and collaborators made efforts to recover Sargassum beds from July 2007 to May 2009. The short-term destination was reforestation in 0.2-hectare areas. As the main factors of Isoyake were assumed to be intensive grazing by sea urchins and/or herbivorous fishes, and short of algal reproductive bodies, reduction of the density of sea urchins and supply of Sargassum embryos were planned. In the 0.3ha areas, 14,600 sea urchins were removed and fences were laid to prevent invasion of sea urchins at the boundary. Mature Sargassum thalli were transplanted on the sea bottom using the 'open spore bags' made of nonwoven cloth. In addition, nets were set to capture floating mature Sargassum thalli to enhance the recruits. After nearly a year later, the treated area was covered with Sargassum and other seaweeds. The fishermen were encouraged by the success and much more motivated for further reforestation.
2011-07-15