Paper short abstract:

By examining the Japanese oyster producers' practice of "seafloor plowing," a method for improving nutrients by disturbing the seafloor sediments, I show how the emerging form of human intervention attempts to balance ecosystem conservation and oyster aquaculture in post-industrial society.

Paper long abstract:

Local producers and fisheries researchers observe poor Pacific oyster growth over the last decade in Hiroshima Prefecture, the largest oyster-producing region in Japan. Changes in the composition of seawater nutrients that results in poor Pacific oyster growth has multiple causes. Since the development of estuarine watersheds in the 1970s, and more recently, the dam construction in the early 2000s, nutrients from the mountains have been unable to reach the sea. Further, some fisheries researchers’ claim sewage treatment, part of efforts to reach the government’s nationwide water quality standards, overpurifies the estuarine waters and thereby causes oyster maldevelopment. To address this latter problem for the Japanese aquaculture industry, local government sewage treatment plants increase the concentration of nutrients in the treated sewage water in winter when the level of phosphorus and nitrogen is low. Yet despite government attempts to address the problem, the nutrient imbalance remains. For local fishery cooperatives dependent on oyster growth for members’ livelihoods, the condition of the seawater is unacceptable. To help restore an appropriate mix of nutrients, members of a local oyster farming cooperative undertake "seafloor plowing," a method for reducing organic pollution while improving the uneven distribution of nutrients by disturbing the seafloor’s sediment layer and supplying oxygen. By examining this fishery cooperative’s attempt to balance ecosystem conservation and oyster aquaculture, I show how this practice of seafloor plowing, as a new form of human intervention, reconfigures multispecies relationships in a coastal aquaculture site in post-industrial society.