Density of the Commercial Spider Crab, Chionoecetes opilio, and Calibration of Effective Area Fished Per Trap Using Bottom Photography

1975 ◽  
Vol 32 (6) ◽  
pp. 761-768 ◽  
Author(s):  
R. J. Miller
Keyword(s):  
Carapace Width ◽  
Live Weight ◽  
Accurate Method ◽  
Effective Area ◽  
Mature Female ◽  
Spider Crab ◽  
Chionoecetes Opilio ◽  
Abundance Estimates ◽  
Crab Density ◽  
Fishing Area

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.

Maturity, Mating, and Egg Laying in the Spider Crab, Chionoecetes opilio

1970 ◽  
Vol 27 (9) ◽  
pp. 1607-1616 ◽  
Author(s):  
J. Watson
Keyword(s):  
Carapace Width ◽  
Mature Female ◽  
Egg Laying ◽  
Minimum Size ◽  
Spider Crab ◽  
Allometric Growth ◽  
Morphometric Measurements ◽  
Chionoecetes Opilio ◽  
Breeding Potential ◽  
Males And Females

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.

Growth Per Molt and Limb Regeneration in the Spider Crab, Chionoecetes opilio

1976 ◽  
Vol 33 (7) ◽  
pp. 1644-1649 ◽  
Author(s):  
R. J. Miller ◽  
J. Watson
Keyword(s):  
Least Squares ◽  
Sexual Maturity ◽  
Carapace Width ◽  
Limb Regeneration ◽  
Percentage Increase ◽  
Spider Crab ◽  
Chionoecetes Opilio ◽  
Size Growth ◽  
Zero Growth ◽  
The Difference

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.

Grasping Behavior of Male Snow Crab Chionoecetes Opilio (O. Fabricius, 1788) (Decapoda, Majidae)

Crustaceana ◽  
1996 ◽  
Vol 69 (2) ◽  
pp. 211-222 ◽  
Author(s):  
Michel Comeau ◽  
Mikio Moriyasu
Keyword(s):  
Size Range ◽  
Wild Population ◽  
Carapace Width ◽  
Mature Female ◽  
Snow Crab ◽  
Second Phase ◽  
Chionoecetes Opilio ◽  
In The Wild ◽  
Solitary Males ◽  
Wide Size Range

AbstractThe grasping behavior of snow crab, Chionoecetes opilio, was observed in 43 males when only male crabs were collectively held in an aquarium. A larger male always grasped a smaller sized male which exhibited submissive behavior similar to a mature female in a mating pair. This grasping behavior was observed in terminal molt larger sized males except for one case observed for one intermolt juvenile male. During the mating season, although a wide size range of morphometrically mature males was present (51.0-131.0 mm in carapace width) in the wild population, mainly larger sized morphometrically mature males (72.1-128.4 mm in carapace width) participated in the mating courtship. A small number of solitary males was observed on the mating ground and their sizes were comparable to the males in mating pairs. Among the males in mating pairs, the larger sized males tend to occupy favorable mating grounds at greater depths, while the smaller sized males are found on less favorable grounds. The grasping behavior observed in the aquarium and in the wild suggests that the male-male grasping behavior appears to be related to the establishment of hierarchy among the mating males. Smaller sized morphometrically mature males appear to be eliminated before the mating pairs are formed and appear on the mating ground. On the mating ground, the second phase of competition among males occurs for favorable mating grounds.

Reproductive Cycle and Fecundity of Primiparous and Multiparous Female Snow Crab, Chionoecetes opilio, in the Northwest Gulf of Saint Lawrence

1993 ◽  
Vol 50 (10) ◽  
pp. 2147-2156 ◽  
Author(s):  
Bernard Sainte-Marie
Keyword(s):  
Carapace Width ◽  
Mature Female ◽  
Snow Crab ◽  
Beam Trawl ◽  
Chionoecetes Opilio ◽  
Quantitative Analyses ◽  
The Mean ◽  
Egg Diameter ◽  
Multiparous Female ◽  
Over Time

A total of 1 691 mature female Chionoecetes opilio was collected by beam trawl in Baie Sainte-Marguerite on seven occasions from April 1991 to May 1992. Quantitative analyses of ovaries, brood, eggs, and spermathecal contents were performed on a subsample of 318 females. Females moulted to maturity in March and April. Development of ovaries and brood were phased and lasted 24–27 mo. Eggs hatched mainly from April to June. Spermathecae contained zero to three ejaculates, and the mean blotted weight of freshly deposited ejaculates was significantly greater in primiparous (0.513 g) than in multiparous (0.249 g) females. The weight of stored ejaculates decreased over time independently of spawning events. Fecundity was correlated positively with carapace width and negatively with mean egg diameter. Eggs of primiparous females were on average 1.4–2.7% larger, but 16.4–22.7% fewer per brood, than those of multiparous females. Some large multiparous females had small broods, due possibly to lesser fertility. Females probably hatch only two broods in a lifetime and produce a total of 81 630 to 83 143 larvae at 57.4 mm carapace width. Primiparous females apparently contribute >40% of larvae produced by the population.

Growth and moulting of wild-born immature snow crabs, Chionoecetes opilio (Fabricius, 1788) (Decapoda, Majoidea), in the laboratory

Crustaceana ◽  
2015 ◽  
Vol 88 (7-8) ◽  
pp. 911-922 ◽  
Author(s):  
Takeo Yamamoto ◽  
Tatsuya Yamada ◽  
Takahiro Kinoshita ◽  
Yuji Ueda ◽  
Hiroshi Fujimoto ◽  
...  
Keyword(s):  
Sea Of Japan ◽  
Probability Model ◽  
Natural Habitat ◽  
Carapace Width ◽  
Laboratory Culture ◽  
The Sea Of Japan ◽  
Growth Indices ◽  
Chionoecetes Opilio ◽  
Model Based ◽  
Snow Crabs

Growth and moulting of wild-born immature snow crabs (Chionoecetes opilio (Fabricius, 1788)) were investigated by laboratory culture experiments. Crabs with 16.2-42.9 mm carapace width caught from the Sea of Japan were cultured at a temperature of their natural habitat (approximately 1°C). The growth indices (size increments at moulting in mm and in % of premoult carapace width) and intermoult period were significantly affected by premoult carapace width, but sex did not affect these variables. Furthermore, we demonstrated that premoult carapace width and days after moulting significantly affected moulting probability and we developed a moulting probability model based on these variables. From this model, the number of days of intermoult periods when moults occurred in 50% of crabs of instars VI, VII and VIII was estimated at 234, 284 and 346 days, respectively.

scholarly journals Trophic habits of the invasive crab Libinia dubia H. Milne Edwards, 1834 from the Gulf of Gabès (Tunisia)

2020 ◽  
Author(s):  
AMANI CHAFFAI ◽  
WAFA RJIBA-BAHRI ◽  
ASMA ABIDI ◽  
FRANҪOISE DENIS ◽  
JAMILA BEN SOUISSI
Keyword(s):  
Feeding Habits ◽  
Carapace Width ◽  
Stomach Contents ◽  
Spider Crab ◽  
Gulf Of Gabes ◽  
Chi Square ◽  
Gulf Of Gabès ◽  
Chi Square Test ◽  
Herbivorous Species ◽  
Stomach Weight

Feeding habits of the invasive spider crab Libinia dubia from the Mediterranean Sea were studied in the Gulf of Gabès (Tunisia) using the frequency of occurrence and points methods. The population was sampled at least monthly between November 2015 and October 2016. Stomach contents of 384 specimens were analysed. Results indicate that L. dubia is an herbivorous species exhibiting clear preferences for algae (ALG) and Magnoliophyta (MAG) (62.03%, 7.13 points and 59.36%, 5.3 points respectively) although Echinodermata (ECH), Porifera (POR), Cnidaria (CNI), Mollusca (MOL), Polychaeta (POL), Crustacea (CRU) and fish (FIS) were accidentally consumed along with Bryozoa (BRY), sediment (SED), and unidentifiable materials (UNM). The diversity of ALG ingested was studied in detail: Chlorophyceae were found in 87.93% of stomachs containing ALG and contributed most of points to the stomach contents (4.18 points) followed respectively by Phaeophyceae (81.03%, 2.27 points) and Rhodophyceae (40.95%, 0.68 points).Very low Vacuity Index was recorded (VI = 2.6%). Ingested items varied significantly with regard to the season (Chi-square test, χ2calculated = 87.86 > χ2theoretical = 7.81, df = 3, p < 0.05) and crab size (χ2calculated = 14.25 > χ2theoretical = 5.99, df = 2, p = 0.026). Insignificant differences were registered by studying Carapace Width-Stomach Weight (CW-SW) relationships (T-test, tcalculated < ttheoretical, p > 0.05). Kruskal-Wallis test was applied so that the composition of crab diet among groups could be compared (H = 1.1, df = 3, p = 0.77). 

Functional Maturity in Small Male Snow Crabs (Chionoecetes opilio)

1988 ◽  
Vol 45 (12) ◽  
pp. 2106-2109 ◽  
Author(s):  
G. P. Ennis ◽  
R. G. Hooper ◽  
D. M. Taylor
Keyword(s):  
Rapid Development ◽  
Carapace Width ◽  
Reproductive Potential ◽  
Snow Crab ◽  
Small Male ◽  
Chionoecetes Opilio ◽  
In Captivity ◽  
Breeding Migration ◽  
High Level ◽  
Snow Crabs

The mean size of male snow crabs (Chionoecetes opilio) in sexual pairs during the annual spring breeding migration to shallow water in Bonne Bay, Newfoundland, decreased from 118.6 mm carapace width (CW) in 1983 to 100.3 mm in 1987. This decrease is due to an increase in males <95 mm CW participating from 1.5% in 1983 to 32.3% in 1987. This change appears to have resulted from a reduced abundance of commercial size [Formula: see text] males due to a rapid development of an illegal fishery on this previously unfished population and, as a consequence, less competition between males for possession of females. The percentages of spermathecae containing new spermatophores for females paired with males <95 mm CW (67%) and those with males [Formula: see text] (79%) were not significantly different. We assumed that each female with new spermatophores had recently mated with the male with which it was paired. Observations on selected pairs in captivity showed that males <95 mm CW are capable of mating with both primiparous and muitiparous females. Our results indicate that small mature males can replace large males in breeding activity in a snow crab population. We conclude that in the male-only snow crab fishery in Atlantic Canada with a minimum legal size of 95 mm CW, population reproductive potential is maintained at a high level despite high exploitation rates on males [Formula: see text].

Neuromuscular analysis of the chela-closer muscle associated with precopulatory clasping in male snow crabs, Chionoecetes opilio

1992 ◽  
Vol 70 (12) ◽  
pp. 2356-2363 ◽  
Author(s):  
C. K. Govind ◽  
A. T. Read ◽  
W. T. Claxton ◽  
R. W. Elner
Keyword(s):  
Carapace Width ◽  
Motor Pattern ◽  
Low Frequency ◽  
Thick Filament ◽  
Thin Filaments ◽  
Chionoecetes Opilio ◽  
Sustained Activity ◽  
Synaptic Potentials ◽  
Slow Fiber ◽  
Snow Crabs

Male snow crabs, Chionoecetes opilio (Majidae), use their modified chelae to retain females for weeks before copulation. Consequently, adaptations for such sustained activity were examined in the chela-closer muscle responsible for clasping. Based on an allometric increase in the ratio of chela size to carapace width, male snow crabs were categorized as morphometrically mature or immature, the former displaying precopulatory clasping more readily than the latter. However, the two types were similar in terms of the properties of the chela-closer muscle, which was examined in this study. The motor pattern during clasping consisted of low-frequency firing of one of the excitor motoneurons, which gives rise to small synaptic potentials. The other excitor motoneuron, which produces large synaptic potentials, fired only when the female struggled during the embrace. The synaptic potentials of both axons showed little if any fatigue at these low firing frequencies. The neuromuscular terminals of these motoneurons displayed areas of synaptic contact larger than most found in other tonically active crustacean muscles. The majority of these synapses had an active site for transmitter release denoted by a dense bar, with many containing more than three dense bars. The closer muscle had typically slow features, with 10 or 11 thin filaments surrounding a thick filament, and sarcomere lengths of 9 – 10 μm. Overall, the closer muscle with its slow-fiber composition, tonic motoneurons, and neuromuscular synapses is well suited to sustained, low-level activity such as precopulatory clasping.

scholarly journals Trophic niches of benthic crustaceans in the Pechora Sea suggest that the invasive snow crab Chionoecetes opilio could be an important competitor

Polar Biology ◽  
2020 ◽  
Author(s):  
Anna Gebruk ◽  
Anna K. Zalota ◽  
Polina Dgebuadze ◽  
Yulia Ermilova ◽  
Vassily A. Spiridonov ◽  
...  
Keyword(s):  
Invasive Species ◽  
Stable Isotope ◽  
Integrated Approach ◽  
Trophic Niche ◽  
Snow Crab ◽  
Ecosystem Structure ◽  
Spider Crab ◽  
Chionoecetes Opilio ◽  
Trophic Niches ◽  
Prey Items

AbstractExpanding human activities alongside climate change, the introduction of invasive species and water contamination pose multiple threats to the unique marine ecosystems of the Pechora Sea in the Russian Arctic. Baseline data on biodiversity and responses to environmental change are urgently needed. Benthic decapod crustaceans are globally distributed and play an important role in fisheries, yet their roles in food webs are less understood. In this study, we used an integrated approach combining stomach content analysis and stable isotope analyses (δ13C and δ15N) to examine the trophic niches of three decapod species in the Pechora Sea including the invasive snow crab Chionoecetes opilio and two species of native decapods, the spider crab Hyas araneus and the hermit crab Pagurus pubescens. Stomach contents of 75 decapods were analysed (C. opilion = 23; H. araneusn = 9; P. pubescensn = 43), and 20 categories of prey items were identified with the most frequently occurring prey items being bivalve molluscs (Ciliatocardium ciliatum, Ennucula tenuis, Macoma calcarea), polychaetes, crustaceans and plant debris. Bayesian ellipse analyses of stable isotope signatures (n = 40) revealed that C. opilio displays an overlapping trophic niche with the two native decapods, providing direct evidence that the invader likely competes for food resources with both H. araneus and P. pubescens. As such, the presence of this invasive species could hold important consequences for trophic interactions, benthic ecosystem functioning and biodiversity. Microplastics were also found to be a likely stressor on this ecosystem, as 28% of all stomachs contained digested microplastics among other items. Long-term studies of benthic ecosystem structure and functioning are now needed to more fully understand the extent to which this new competitor may alter the future biodiversity of the Pechora Sea alongside the additional stressor of digested plastics.

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