Abstract
Horizontal distribution pattern and carapace size composition were derived for snow crab Chionoecetes opilio from data collected by long-line trap and Danish seine surveys conducted at 242-244m depth in the Japan Sea off Kyoto Prefecture in May 1990. Distinct difference in horizental distribution was noted between male and female crabs, while samplings were made at the same contour in depth. Estimates of dispersion of unit patchness for mature males ranged from 100 to 200m within a large schooling dispersion (600-1, 500m). Mature female crabs might dis-perse rather densely ranging from 100 to 300m within a large school dispersing over 1, 500m and immature females ranging from 100 to 300m within a large dispersion (400-900m). It is surg-gested that growth and/or maturation of snow crab may influence horizental distribution pattern, as well as seasonal aggregation. It was clearly showed that the carapace size compositions of crab were different between two catches by the trap and the Danish seine, which was mainly due to the differences in the frequency distribution of sub-legal male crab and mature female crab. The results showed that the trap has higher selectivity towards the large sub-legal crabs more than 80-90mm carapace width. Es-timated mean carapace width from two gears were 51.0, 67.6, 86.6, 106.9mm for males and 51.8, 68.7, 79.0mm for females.
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