Estimation of catches for shortfin mako, Isurus oxyrinchus, caught by Japanese offshore and distant water fisheries
This working paper provides with estimation of catches for shortfin mako caught by Japanese offshore (1994 and 2019) and distant-water longline fishery (during 1992 and 2019) in the North Pacific. Since the landings of sharks is frequently underestimated due to the lower value than any other teleost species such as tunas and swordfish, total catches including retained and discard/released catches were estimated using a product of the annual standardized CPUEs and the fishing effort. Two annual catch data in number of shortfin mako caught by shallow-set (1994 and 2019) and deep-set (1992 and 2019) fisheries were used. The catch number was converted into the catch weight using the average weight of shortfin mako by area and season. The results showed that the total catches of shortfin mako in the North Pacific caught by Japanese offshore and distant-water longline fishery had gradually increased since 1992 until 2007 and reached at 1144 tons, and then it had gradually decreased due to the continuous reduction of total fishing effort.