Faculty of Fisheries, Kagoshima University, Kagoshima, Kagoshima 890-0056, Japan
Expanded polystyrene (EPS) floats are used abundantly for the floats of oyster farming rafts in Hiroshima Bay. This paper investigated the occurrence of stranded debris of foamed plastics, stranding and unsuitable use of EPS floats on the coast of Eta and Kurahashi Islands in the Bay. Stranded debris of foamed plastic was collected from sand samples of 34 sites. Stranded floats on the beach and unsuitably used floats without covers for mooring buoys and fenders on the sea were observed visually at 58 sites along 48.6 km of coastline.
The total number of collected debris was 245,656 items. Plastics accounted for 99.9% of the total number. Foamed plastic fragments accounted for 99.5% of the total, the size of under 10.0 mm represented 98.5% of the fragments, and the average density was 44,521.3 pieces per m2. Unsuitably used floats totaled 6,760, and the density was 140.7 pieces per harbor. The density of stranded floats was 1.1 pieces per km. The densities of unsuitably used floats, stranded floats and foamed plastic fragments on the coast of Eta Island were higher than those of Kurahashi Island.