Field observation of wave-induced circulation in ormer [Sulculuc diversicolor diversicolor] fishing ground [in Hachijyo Island, Japan]

Field observations and analysis of wave-induced circulation in Masawa, Hachijyo Island were made and the generating mechanism of the circulation was investigated by introducing the radiation stress concept. Results show that circulation cells exist constantly, and the differences between the gradient of the radiation stress and mean water level gradient, which are the driving forces to induce wave current, are produced by the differences of local wave height associated with the refraction of wave due to the undulation of seabottom topography. The survey results show that when the offshore current flow is great, the circulation cell on the downstream side is strengthened, while that on the upstream side is weakened. Moreover, in the clockwise and anticlockwise cell forming area, the marine algae community and the area densely inhabited by ormer Sulculus diversicolor diversicolor correspond well with one another.