Teruhisa Komatsu*, Kenichi Tatsukawa*, Kenichi Ishida*, Chiaki Igarashi*, Sayeeda Sultana*, Masahiro Takahashi**, Yasuaki Matsuoka***

* Ocean Research Institute, University of Tokyo
**Mitsubishi Space Software Co., Ltd.
***Toyo Corporation

Coastal fishing is very active along Sanriku Coast facing Northwestern Pacific due to the rich nutrients and warm water that is caused by the encounter in these waters between the cold water current, Oyashio, and the warm water current, Kuroshio. This produces great primary production and gathers commercially important fish species on the Sanriku Coast. There are also lots of aquaculture facilities for oysters, scallops, sea pineapples, and algae in the rias-type bays of the Sanriku Coast.

Seagrass and seaweed beds also play an important role in marine coastal ecosystems. They support flora and fauna including epiphytic organisms, and coastal fisheries productivity. Seagrass beds contribute to the marine environment, for example, by stabilizing bottom sediments, maintaining coastal water quality and clarity. This is essential for thesustainable development of coastal fisheries and the maintenance of sound coastal ecosystems for future generations. For this purpose we must know the present state of coastal zones and monitor not only the natural environment but also human activity, especially coastal fisheries. We made a study on the development of methods for mapping the coastal zone along Sanriku Coast.

We examined mapping methods using satellite imagery and acoustic survey. Since there are a lot of aquaculture facilities in the coastal waters, it is necessary to localize and count them for the management of coastal fisheries. Thus we developed an easy method to map and count them using IKONOS satellite images with a high resolution (1m x 1m). Processing IKONOS imagery of Yamada Bay, two types of aquaculture facilities, wood-raft type and buoy-and-rope type, were identified and examined.
We also developed a mapping method for seagrass beds to quantify the volume of seagrass using a multi-beam sonar for the first time. We applied the method to map a seagrass bed of Zostera caulescens in Otsuchi Bay on the Sanriku Coast. The multi-beam sonar detected the distribution of Z. caulescens and its volume. Our study demonstrated that the method of using a multi-beam sonar is effective for mapping and quantifying the spatial distribution of seagrass beds.

Two methods developed in this study can be applied not only to rias-type bays but also to other coastal waters in developing countries.

presentation