Along the Okhotsk Sea coast of Hokkaido, the scallop (Patinopecten yessoensis) seabed sowing cultivation has been successfully performed with the four-year cycle system of mariculture. The scallop aged four is caught by the pair of dredge nets of a 14GT size vessel. However, scallop dredging operation consists the cycles of the strenuous works, such as the dredge net hauling, emptying and sorting of the catch. In this report, the author explained the field investigation of the scallop dredge fishery conducted in Tokoro fisheries cooperative association. And a method for simulating the dredging operation was developed with consideration of the cumulative catch in the fishery ground. It showed that scallop catch efficiency decreases remarkably as the cumulative catch become close to the initial stock. The relationship between the scallop dredging operation characters and the cumulative catch could be evaluated from this calculation model.