The seafood production in Korean waters has been decreasing since mid-1970's due to depletion of fisheries resources caused by overexploitation and environmental deterioration. On the other hand the demand of seafood as a source of animal protein and export supply has been increasing continuously. And thus, Korea has become an importer from one of the top ranking exporters in terms of fisheries. Korea has put $600 million to enhance fisheries resources and to modernize aquaculture technology, and has achieved some success but in fact, Korean fishermen have suffered by poor yields in coastal fishing grounds while aquaculturists have distressed by ever increasing production cost, mainly of feed costs and wages, and frequent outbreak of fish disease in aged culture grounds. On the other hand, consumption of seafood per capita has increased from 27kg in 1970' to 54.2kg in 2006 and the 42% of the total consumption of animal proteins are depending on marine animals. The self-sufficiency of seafood in Korea dropped to 66.4% and recorded $1.6 billion of trade deficit which was equivalent to 1 million tons of fish products in 2006. Expansion of aquaculture seems to be a good solution however, as Korea does not have enough coastal surface to meet its requirement, the only solution is marine ranching. The concept of marine ranching is to increase the incomes of local fisherman, and to supply sea food in stable base, and to contribute for developing the fishing village through managing coastal fisheries resource in environment-friendly and ecologically sound way. After a nine-year study effort, Korea Ocean Research and Development Institute has completed the first commercial size marine ranch on 26 June 2007 in Tongyeong, southern cost of Korea.