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Spider crabs, Chionoecetes opilio, were held in the laboratory for observations on carapace width increments and limb regeneration per molt. The merus (the longest limb segment) of autotomized limbs regenerated to 48 and 73% of their full length, irrespective of crab size, on the first and second molt, respectively. Fitting least squares regressions to percentage increase of carapace width per molt (Y) vs. premolt carapace width (X [in millimeters]) gave the following equations: immature males Y = 40.7 − 0.363X; immature females Y = 45.3 − 0.444X; mature males Y = 14.2 + 0.051X; and females’ terminal molt to maturity Y = 14.0 − 0.014X. Only the slopes for the first two equations differed significantly from zero. Growth per molt decreased with sexual maturity for both sexes and was significantly less for females molting to maturity than for mature males of the same size. Growth per molt for immature females was significantly greater than for immature males, but the difference was slight.

The number of eggs attached to pleopods of Chionoecetes bairdi and C. opilio from the southeastern Bering Sea increased at a rate proportional to about the 3.4 and 2.7 power of carapace width, respectively, but for C. opilio from the Gulf of St. Lawrence it increased to the 4.2 power. The range in carapace width and number of eggs for crabs from the Bering Sea of a given carapace width were considerably greater for C. bairdi than for C. opilio. In the southeastern Bering Sea, the reproductive potential for adult females of C. bairdi with mixed spawning history is approximately 4 times greater than that of C. opilio spawning for the first time. Chionoecetes opilio females with mixed spawning history in the Gulf of St. Lawrence carry more eggs for a given carapace width than first-time spawners from the southeastern Bering Sea. Our data were not sufficient to resolve the question of relative number of eggs for crabs of various ages.

Bottom photography was found to be a more accurate method of censusing the commercial spider crab, Chionoecetes opilio, than trawling or sight counting from a submersible. Because of their highly aggregated distributions, estimating abundance of mature female crabs and immature crabs of both sexes was not practical by any method. The larger males (≥ 40 mm carapace width), including those of commercial value, approached a random distribution, however; and abundance estimates for four study areas ranged from 5.2 to 9.2 crabs/500 m2 and from 2.2 to 4.2 kg live weight/500 m2. To permit results of exploratory fishing with traps to be converted to crab density and size of crab stocks available to a commercial fishery, a commercial crab trap was calibrated for "effective" area fished. The effective fishing area per trap averaged 4100 m2 over four study areas.

Ectocotyla hirudo (Levinsen, 1879) is redescribed and recorded for the first time from the gills and branchial chambers of Chionoecetes opilio and Hyas araneus. Problems arising from previous descriptions are resolved through comparison of freshly collected material, at different times of the year, with type material of Coleophora sp. and the type material of E. paguri Hyman, 1944, both of which are shown to be identical to the present material. Accordingly, E. paguri Hyman, 1944 is regarded as a junior synonym of E. hirudo (Levinsen, 1879). A new species, E. multitesticulata, is described and recorded also from C. opilio and H. araneus. Ectocotyla multitesticulata differs from E. hirudo primarily in the larger size of the worm, the greater number and size of the testes, the size of the egg capsule, and in the differences of the karyotype. The genus Ectocotyla is discussed in relation to closely related genera (Peraclistus, Minona, and Preminona) in the family Monocelididae. Key words: turbellarian systematics, Proseriata, Monocelididae, Ectocotyla, crab commensal

Fecundity varies from year to year in blue mussels (Mytilus edulis) from Petpeswick Inlet, N.S., and from Bellevue, Nfld. This observation is consistent with recent theory that suggests that reproductive effort (that proportion of the energy budget allocated to reproduction) should be variable in animals such as marine bivalves that are unable to "predict" the quality of the environment for their juveniles. Estimates of fecundity in the sea urchin (Strongylocentrotus droebachiensis) and the snow crab (Chionoecetes opilio) are also presented. Reproductive effort increases with advancing age in the three species of invertebrates studied, although in the mussel the transition from growth to reproduction is more gradual than it is in the sea urchin or the female snow crab, which exhibit early growth and delayed reproduction. The degree to which the growth and reproductive phases are separated in each species may be determined in part by the predictability of the food supply. The allocation of resources primarily to growth rather than to reproduction in young (small) individuals may be seen as a response to selective pressure resulting from higher mortality and from competition. Key words: growth, production, reproductive strategy, energy partitioning, marine invertebrates, gametes

The CGS Salvelinus collections of decapod crustaceans from south Beaufort Sea to Cambridge Bay in 1960–65 comprised 1830 specimens of 15 species. Five of the species were not previously recorded from this area. Most abundant species were Sabinea septemcarinata and Eualus gaimardi. Eualus macilentus and E. stoneyi were confined to Bathurst Inlet. Westward setting currents along the Beaufort Sea coast mediate against incursions by Pacific species but Chionoecetes opilio, Hyas coarctatus alutaceus, and a species of Pagurus seemed to have overcome this condition. The species in which the highest percentages of females presumably reproduced annually were Spirontocaris phippsi, S. spinus, and S. septemcarinata.

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Muscle tissue of the queen crab, Chionoecetes opilio, contained 0.75% lipid, 78.8% of which was phospholipid (chiefly choline phosphatides) and the balance mainly cholesterol. Viscera contained 13.6% lipid, the bulk of which was triglyceride. Fatty acid composition was generally similar to that of other marine species. However, 20:5ω3 was the major polyunsaturate (rather than the more usual 22:6ω3) and within the 18:1 series, the ω7 isomer was present in unusually large quantities.

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Morphometric measurements and gonad examination of the spider crab, Chionoecetes opilio, showed that 50% maturity occurred at about 57 and 50 mm carapace width for males and females, with minimum sizes at maturity of 51 (males) and 47 mm (females). Both sexes were mature at sizes considerably below the commercially acceptable size of 4 inches (102 mm) carapace width. After maturity, positive allometric growth was demonstrated for males. Females do not moult after reaching maturity. The small vasa deferentia found in soft-shelled mature males suggested that only hard-shelled males were capable of mating. A hard-shelled male successfully mated with a soft-shelled mature female. Field and laboratory observations suggest that more than one brood is commonly produced from one mating.The minimum size limit for commercial landings allows some mature males capable of mating to be left on the fishing grounds. Retention of this limit seems unlikely to affect the breeding potential of the population.

During the week-long precopulatory embrace, the male spider crab, Chionoecetes opilio, held the female, even when attacking intruding males. Before a 45-min copulation period the male assisted female ecdysis. During the postcopulatory embrace spermatophores flowed onto the pleopods of the female. Polygamous males as small as 60 mm width mated with larger females. More than one fertile egg batch was frequently produced from one mating. Females mated successfully up to 95 hr after molting. Hard-shelled females seemed incapable of mating. The probable mating season is February through April and continued recruitment seems assured.