Abstract

Data from surveys conducted between 1989 and 1992 were used to examine fishing mortality and struck-and-lost rates in three major operating grounds of the Japanese Dall’s porpoise harpoon fishery. The catch rate (number of individuals caught per operating hour) was higher in the Sea of Japan (0.82) and the Okhotsk Sea (0.53) than in the Pacific off Sanriku (0.19). The mean struck-and-lost rate was higher in the Sea of Japan and the Okhotsk Sea (10.5% and 9.8%. respectively) than in the Pacific off Sanriku (5. 0% ), although there was considerable variation. The proportion of struck but lost porpoises that were dead or expected to die was estimated to be 33.3% in the Sea of Japan, 14.3% in the Okhotsk Sea and 100% in the Pacific off Sanriku. Total fishing mortality (including struck-and-lost animals) was estimated to be 1.10-1.14 times higher than the number of Dall’s porpoises landed.