ズワイガニに関する漁業生物学的研究-VI

Abstract

The number of ovarian eggs and eggs held in the pleopods of the tanner crab, Chionoecetes opilio, were examined from specimens captured off Wakasa Bay of the Japan Sea. The number of eggs may be expressed as a function of the carapace width (X, mm).(a) For mature eggs in the ovary just before spawning, N1=3, 151X-145, 676 (correlation coefficient: r=0.9895);(b) For fertilized eggs, held in the abdominal pouch two to four months after spawning, N2=2, 295X-106, 597 (r=0.9902);(c) For fertilized eggs, one to three months before hatching, N3=1, 014X-25, 366 (r=0.9870).As diagnosed from the parameters of these equations, the number of eggs increase with progressive enlargement of the carapace width, although the rate of increase differs with the different developmental stages of the eggs. The ratio of the number of fertilized eggs shortly before hatching to mature ovarian eggs is quite inversely proportional to the increase in carapace width.The number of fertilized eggs shortly before hatching carried by a crab in an average carapace width of 77.4mm corresponds to about 54% of the number of mature ovarian eggs in a crab of comparable size. It is believed that about 50% of the deposited eggs may be lost during the course of embryonic development.