Owase Fisheries Research Laboratory, Mie Prefecture Fisheries Research Institute, Owase, Mie 519-3602, Japan
In order to consider measures for improving sediment quality at fish farms in the southern part of Mie Prefecture, Japan, we surveyed the sediment quality (acid volatile sulfide [AVS] content), farming intensity (fish density, daily feeding rate, fish cage area, and migration of fish cages) and environmental characteristics (water depth and current velocity) in red sea bream Pagrus major farms. Regression analyses revealed that the daily feeding rate, fish cage area, migration of fish cages, water depth, and current velocity influence spatial variation of AVS levels. AVS level was particularly influenced by the current velocity, an increase in which was associated with a reduction in the sedimentation rate of organic matter on the seabed and increase in supply of dissolved oxygen. Thus, measures to improve sediment quality at fish farms must be determined based on both the farming intensity and environmental characteristics.