Distribution ratio of fish amount in each part of set-net

In order to identify the distribution ratio of fish amount in each part of the main net area of set-net, experimental operations were conducted in fou r different sites of set-net fishing ground Chiba, Iwate, Ishikawa and Kana gawa prefectures. Each set-net of various size and shape has the nonreturn device of slope or funnel net, which defines the front part against: the re ar part of final stage for the hauling procedure. Distribution ratio of fis h amount estimated as 20:80 on the small set-net in Tateyama Bay, Chiba pre fecture, 31:69 for chum salmon Oncorhynchus keta on the small set-net in Ot suchi Bay, Iwate prefecture, 10:90 for sardine Sardinops melanostictus on t he small set-net in Kanazawa area, Ishihawa prefecture, 27:73 on the large set-net in Hiratsuka area, Kanagawa prefecture. Fish density calculated fro m net volume and average fish amount in each set-net showed the higher valu e in the rear part of non-return device. The results suggest the reasonable performance of the non-returning function in the present gear designing, w hile farther modifications of fishing gear and methods are required from th e view points of minimizing the catch loss in the front part of nonreturn d evices.