Distribution of manufactured floating marine debris in near-shore areas around Japan

摘要

In order to analyze the influence of floating marine debris (FMD) on aquatic livings in the sea, many observations for abundance and composition of debris on the shore have been carried out in Japan (e.g. Yamaguchi, 2003) as well as in other countries (e.g. Gregory and Ryan, 1997; Walker et al., 1997; Barnes, 2002). Information on the shore, however, represents only the fraction of marine debris that has been cast ashore. The major impacts caused by FMD occur while it is afloat (e.g. Walker et al., 1997). For a full understanding of the effect of FMD on aquatic livings, it is indispensable to carry out surveys at sea. The abundance and composition of FMD have been studied actively in the North Pacific (Venrick et al., 1973; Matsumura and Nasu, 1997). Based on the investigation throughout the North Pacific during 1986-1991, the density of FMD in near-shore areas around Japan was in the category of high level (Matsumura and Nasu, 1997). A high-south and low-north trend can be observed for the density of manufactured FMD in near-shore areas around Japan in the past study (Matsumura and Nasu, 1997). However, this trend has not yet been confirmed. The aim of this note is to investigate regional distribution of manufactured FMD around Japan and to confirm the trend.