Abstract
Reproductive ecology of female tanner crab Chionoecetes opilio was studied by the use of six samples caught by traps and trawl net in the southwestern Okhotsk Sea from 1970 to 1971.
Frequency distribution of the carapace width of the mature female in range 46-95mm were distinguished into several length groups composed of normal distribution with distinct modes, presumably corresponding with the plural molting instars in mature female.
Main spawning season was restricted from May to June. Gonad index (IGI) showed custo-marily bimodal distribution for most of the year to suggest a reproductive cycle with two year period.
Individual variations of five measurements in the reproductive characteristics were analyzed by means of principal component analysis, consequently, variations of total egg numbers and clutch weight in the pleopods are both chiefly controlled by body size. On the contrary, the size of an egg shown as egg numbers per gram clutch weight, has a tendency to be independent withthe body size.
