Bivariate and multivariate analyses of allometric relationships between chela size and carapace size of snow crab, Chionoecetes opilio, show that mature males are recognizable by morphometry. The most simple procedure is to plot logarithms of chela height (Ch) against logarithms of carapace width (Lc). Data from mature and immature males fit into two distinct ellipses with parallel major axes. The discriminant function Y = −0.78893 loge. Lc + 0.614488 logeCh + 1.76051 will assign individuals to the correct groups in 99% of cases (for mature males: Y > 0). Spermatophores are present in the vasa deferentia of all males larger than 60 mm Lc. The molt to morphometric maturity occurs later at Lc sizes ranging from 60 to 120 mm; it is identified as final. Only morphometrically mature males larger than 96 mm Lc have been observed to mate efficiently with multiparous females in intermolt and be functionally mature. In the catch, as many as 40% of males larger than the minimal legal size of 95 mm can be immature.

The growth and spatial distribution of postlarval snow crab (Chionoecetes opilio) from a relatively unexploitated stock in Bonne Bay, Newfoundland (Gulf of St. Lawrence), were described from the analysis of size distributions from trawls and a dredge sampled between 1988 and 1993. Immature crabs molted twice a year for instars I-V and then molted annually until females reached a terminal molt at maturity (instar X or XI) and males a juvenile stage (instar VIII). Thereafter, juvenile males could molt to another juvenile size, skip a molt, or achieve a terminal molt at the onset of the morphometric differentiation of their claws depending on the relative abundance of mature males. The life expectancy of females and males was 13 and 19 years, respectively. Males should recruit to the commercial size of 95 mm carapace width at instar XII, 9 years or more after settlement. Relative abundance of early benthic to commercial-size individuals suggests that small immature crabs (instar V) migrate from shallow rocky to deep muddy bottoms. The patchy spatial distribution observed for the snow crab appeared to be determined more by substrate and intraspecific factors than by depth. Seasonal movements to shallow waters by larger animals was related to density- and temperature-dependent factors associated with the reproductive and growth cycle.

The relationship between chela height (CH) and carapace width (CW) of male snow crab, Chionoecetes opilio, goes through three allometric stages. The "immature stage" (mostly < 34 mm CW) evolves into a "juvenile stage" (34–120 mm CW) through a "juvenile molt" defining a change in allometry marked by an angular point around 34 mm CW. Fifty percent of males reach gonad maturity, defined by the presence of spermatophores inside the vasa deferentia, at an estimated size of 34 mm CW) The third allometric stage, "morphometrically mature," is separated from the juvenile stage by a "molt to morphometric maturity" at sizes ranging from 50 to 120 mm CW. Juvenile males have smaller claws than morphometrically mature males of the same size. This secondary sexual character is justified by a specific behavior of the males holding the pereipods of the female in one chela during precopulatory embrace. Male snow crab efficiently mate in nature with intermolt multiparous females only after reaching morphometric maturity. Therefore, the presence of spermatophores is not the sole determinant factor necessary for male copulation. Juvenile males larger than the minimum legal size of 95 mm CW are harvestable before, they may efficiently mate.

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A B S T R A C TThe maturity and reproductive cycle of female American lobsters (Homarus americanus) were investigated in the southern Gulf of St. Lawrence (sGSL), Canada. The onset of sexual maturity of female lobsters can be established by observations of the ovarian condition, either color or weight, and staging of cement glands but cannot be detected by the morphometry of their abdomens. Females reached 50% maturity between 68.7 mm and 73.3 mm carapace length (L C ). There was a significant geographic difference (P , 0.005) in the size at 50% maturity established by the ovarian development techniques but not by the cement-gland staging technique. Also, there were no annual significant differences (P . 0.005) between the ovarian development techniques used at a single site between 1994 and 1997. To study the reproductive cycle of females, molt stage, ovarian development, and egg spawning were monitored by dissections at the laboratory and by tagging studies in the field. The majority (80%) of small mature females (L C , 120 mm) in the sGSL had a typical two-year reproductive cycle with molting (with copulation) and spawning in alternating years. However, up to 20% of multiparous females ranging between 65 mm and 109 mm L C could spawn in successive years instead of the generally accepted twoyear cycle, and some could even molt and spawn during the same summer. Similarly, up to 20% of primiparous females could molt and spawn (for the first time) in the same year instead of spawning the following year. A small percentage (5%) of small mature females could also skip molting or spawning for a year. Temperature data suggested that the length of the female reproductive cycle, and possibility of molting and spawning in the same year, were related to the number of degree-days in a particular season.The American lobster (Homarus americanus Milne Edwards, 1837) is one of the most valuable commercial species landed in Eastern Canada. One of the key elements to achieve a healthy fishery is assuring a good egg production by allowing females to spawn before being captured (Anonymous, 1995). Hence, a good knowledge of the female size at maturity is essential for a sound management of the fishery and is often used as one of a suite of references to define the minimal legal size at capture for the lobster (Campbell, 1985).Lobster mating in the southern Gulf of St. Lawrence (sGSL) occurs between July and September. Small female lobsters (carapace length , 120 mm) are thought to follow a two-year reproductive cycle (Aiken and Waddy, 1982). In a typical cycle, females are molting and mating during the same summer, extruding the eggs the following year, and carrying them attached on pleopods under the abdomen for nearly another year. This two-year reproductive cycle may be shortened to one year for primiparous females by fluctuation of environment factors, mainly temperature (Templeman, 1934(Templeman, , 1936Waddy and Aiken, 1992;Waddy et al., 1995). The reproductive cycle is also influenced by the female size, as larger females ...