Discards in Japanese Marine Capture Fisheries and their Estimation

Abstract

By catch focused here is incidental catch to be discarded at sea and those utilised is dealt little. This is because, as widely stated, by catch is not necessarily a negative practice as there are many fisheries which are feasible with by catch in addition to the principal species. It is important to segregate by catch and discard issues. It may provoke unnecessary and unproductive contradiction, if by catch as a whole is dealt in the same line with discards. This report firstly overviews the structure of the fishing industry of Japan and its statistics in view of its sectors and landing. This aims at illustrating its basic characters and changes for the recent years. Secondly, the report summarises available information on discards from a sector to sector. It estimates, then, the amounts of discards by individual sectors and, subsequently, the total discard by the Japanese marine capture fishery as a whole. The last part of the report discusses improvement of methodology in discard researches. In this report, only publicised data were utilised for discard estimation with exceptions of those recorded by the author or the author's group. Discard ratios were either directly adopted or secondarily evaluated from those records.