A variety of substrates have been used for collecting seed scallops. The traditional collectors, like cedar leaves and scallop shells, have been replaced in Japan by polyethylene-mesh bags attached to long-line systems. The long linesvary in length from 50 to 100m and the number of bags attached to each line depends on the water depth and the number of branch lines. The bags are filled with artificial substrates such as mesh monofilament, soft netlon, nylon and plastic meshes and rubberized fibre. Any substrate with a clean surface can be used for collecting seed of the European scallops C.maximus and C. opercularis. The mesh size ofthe bag depends on the local conditions including the silt load in the area. The mesh is selected with a view to facilitating free water flow, at the same time preventing the escape of the settled spat and clogging of the meshes by silt. The collectors are laid out at times of spatfall, which are forecast on the basis of close monitoring of water temperature, spawning and larval abundance.