1Kyoto Institute of Oceanic and Fishery Science, Kyoto 626-0052, 2Department of Fisheries Resource Management, Tokyo University of Fisheries, Tokyo 108-8477, Japan
In order to estimate the mortality coefficients of adult female snow crab Chionoecetes opilio in the waters off Kyoto Prefecture, tagged ones were released in fishing ground in the closed season in 1990 (group I), 1995 (group II), 1996 (group III) and 1997 (group IV). Further, in the water of 270m depth inside the preserved area (13.7km2), tagged females were released in 1995 (group V). Using maximum likelihood approach with the recoveries every 1-fishing year term after release in the each group, total mortality coefficients (Zi) for groups I and II~IV were estimated to be 1.699 and 0.975~1.181year−1, respectively. On the other hand, Zi for the group V was estimated to be 0.561year−1. The difference of Zi is discussed. Recent decrease in amount of discard by Danish seine fishery was considered to cause it because a part of the fishing ground where the fishery exploited the crab as bycatch had been seasonally closed.