Temporal and Spatial Variation on Water Environment and Fishery Resources in Osaka Bay

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Temporal and Spatial Variation on Water Environment and Fishery Resources in Osaka Bay

Proceedings of the Twenty-third (2013) International Offshore and Polar Engineering www.isope.org Anchorage, Alaska, USA, June 30–July 5, 2013 Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE) ISBN 978-1-880653-99–9 (Set); ISSN 1098-6189 (Set) Temporal and Spatial Variation on Water Environment and Fishery Resources in Osaka Bay Kohji Uno, Ayumi Kinoshita, Gozo Tsujimoto and Tetsuya Kakinoki Department of Civil Engineering, Kobe City College of Technology Kobe City, Hyogo Prefecture, Japan N ABSTRACT Osaka bay located in western Japan is one of the famous semi-closed water areas in Japan. Around this bay, the natural beach almost completely disappeared due to the development of the seafront zone. On the other hand, former Osaka bay has rich fishery resource; it was Japan Sea called “Chinu-no-Umi” which means “sanctuary for black sea bream”. The environmental rehabilitation of Osaka bay is citizen’s longtime hope. In this study, first, we divided Osaka bay into 5 sea areas and Osaka bay examined temporal and spatial change (1973-2005) on water quality, JAPAN such as COD (Chemical Oxygen Demand) and DO (Dissolved Oxygen). Second, we also examined temporal and spatial change on the amount of catches of Japanese blue crab and black sea bream. Japanese blue crab and black sea bream are the symbol of wide-ranging and benthic Pacific Ocean animal in Osaka bay, respectively. Finally, using the statistical approach, the relationship between water quality improvement and the recovery of fishery resources was clarified. Kobe City KEY WORDS: Osaka bay; water quality; mud property; fishery Akashi strait Osaka City resources; black sea bream; Japanese blue crab. INTRODUCTION Harima-nada Osaka bay The Osaka bay (Fig. 1) is well known as one of the semi-closed water Kansai Int. Airport area in JAPAN. In this area, water quality improvement has been permanent problem. Former Osaka bay was called “Chinu-no-Umi”, “Chinu” means black sea bream, “Umi” means sea in Japanese, respectively. Therefore, “Chinu-no-Umi” was the word expressing the Kitan strait Awaji Island rich fishery resources in former Osaka Bay. However, after the World War II, with the aim of reducing the storm surge damage and the Kii channel functional enhancement of distribution productivity, many shore Fig. 1 Osaka bay protection facilities were well maintained along the coast line in the bay. As a result, aggravation of water quality has been progressed and fishery resources have been reduced. In this study, using some results of environmental investigations in Osaka Bay, first, the time series of water quality and sediment property In recent years, some countermeasures with the environmental was presented. Next, the time series of fishery resources in Osaka bay improvement techniques for degraded Osaka bay have been conducted was grasped by statistical data in Osaka prefectural fisheries by the governments and the water quality shows some signs of experiment station. Finally, using noticed above data, the relationship improvement. However, Osaka bay has been on way to the between the effect of water quality improvement and the recovery of rehabilitation. the fishery resources in Osaka bay was examined. 671.

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