Several kinds of double sheet net were tested for salmon drift-net fishing. They were specially designed for experimental operation and are constructed by the body of net with small mesh and outer wall with large mesh. The body and the wall of the net are about the same in depth and are connected each other with short hanging lines at appropriate positions.
Three different kinds of such double sheet net were prepared by adjusting mesh size of of wall net and length of hanging lines that connect body and wall together. These were put on experiment on board the Kitagami-Maru in the North Pacific Ocean during the 1961 fishing season. Two different types of double sheet net and single sheet net without wall were also tested in 1962 on board the Shinyo-Maru.
On the basis of the results obtained from these experiments, 142±14% increase of salmon catch is expected by appending an outer wall that has mesh size three times larger than that of body net.