MOLTING AND MATING OF SNOW CRABS, CHIONOECETES-OPILIO (O-FABRICIUS), IN SHALLOW WATERS OF THE NORTHWESTERN GULF OF SAINT LAWRENCE

Chionoecetes opilio in baie Sainte-Marguerite, Gulf of Saint Lawrence, were sampled by beam trawl in spring from 1988 to 1991 and by divers in March 1991 to document an hypothesized annual moult in shallow waters. Each spring, C. opilio occurred at 4-20 m of depth where 29.3-97.3% of males and 20.3-81.4% of females were moulting or recently moulted. Males and females greater-than-or-equal-to 25 mm carapace width (CW) moulted only on bottoms < 60 m. Females were mature at greater-than-or-equal-to 39.6 mm CW and males were morphometrically mature at greater-than-or-equal-to 40.4 mm CW. Overall, 0.3% of morphometrically mature (N = 575) and 23% of morphometrically immature (N = 826) males greater-than-or-equal-to 40 mm CW, exclusive of soft-shelled, had a visible second carapace. These and other data support the hypothesis of a terminal moult coincident with morphometric maturity. Pubescent females mated with males 59.9-109.3 mm CW (88% were < 95 mm CW), 97% of which were morphometrically mature (N = 120). Mean size of these males was greater than that of males grasping immature females or other males, indicating male competition for pubescent females. Morphometrically mature males were larger on bottoms > 80 m deep, where multiparous females concentrated, than on shallower bottoms.