Abdomen allometry, ovary development, and growth of female snow crab, Chionoecetes opilio (Brachyura, Majidae), in the northwestern Gulf of St. Lawrence

Abstract

Growth and maturation of female snow crab (Chionoecetes opilio) in the northwestern Gulf of St. Lawrence were elucidated using carapace size-frequency distributions, indices of molting activity, ovarian mass, and laboratory and field measures of growth per molt. Females develop in three major stages: immature, with narrow abdomen and no detectable ovaries; prepubescent, with narrow abdomen and previtellogenic followed by vitellogenic ovaries; and adult, with broad abdomen and reproductive capability. Additionally, there is an ephemeral pubescent stage represented by females temporally close to the maturity molt. A reduction in the rate of carapace and abdomen growth occurs at the passage from immature to prepubescent, because energy is diverted into germinal growth, and adulthood is reached at a terminal molt to maturity. The pattern of abdomen growth relative to carapace is complex, consisting in successive phases of low, high, and again low positive allometry with increasing size of immature-prepubescent females. Over the period 1989-1996, a few females became adult at instar VIII at 4.5 years postlarval age, but more commonly, maturity occurred at instars IX and X at ages of 5.5 and 6.5 years, respectively. Average size at maturity may be temperature dependent, and within cohorts, larger females may mature earlier than smaller females.