Carapace Width Of Females Research Articles

Struktura populacije atlantskog plavog raka, Callinectes sapidus na istočnoj obali Jadrana (Hrvatska, Crna Gora)

The Atlantic blue crab, Callinectes sapidus, is a highly invasive species that poses a significant threat to Mediterranean ecosystems. In the last two decades, it has become established in several marine and estuarine areas of the eastern Adriatic Sea, resulting in a decline in commercial catches and damage to fishing gear. This article reviews the current status of blue crab invasion in Montenegro and Croatia and analyses its abundance and population structure. Overall 619 crabs were sampled (male:female ratio, 1:1.91). Both carapace width and weight differed significantly between males and females, with males having a wider carapace and more weight. There was a significant difference in carapace width and weight among sites. For the total population, the mean male and female carapace width was 130.3 ± 30.8 and 108.8 ± 41.4 mm, respectively. In addition, the mean male and female weight was 187.2 ± 85.6 and 132.5 ± 39.1 g, respectively. Coefficient b between the weight and carapace width of blue crabs was significant at all locations, although it varied between males and females. This work will also document the impacts of the blue crab invasion on local ecosystems and provide comprehensive overview of populations structures and shed light on this important aspect of blue crab ecology.

Population Structure and Reproductive Biology of the Endangered Crab Deiratonotus japonicus (Brachyura, Camptandriidae) Surveyed for Nine Years in the Kita River, Japan

Deiratonotus japonicus (D. japonicus) is known as a near-threatened species, because of the changing conditions of its habitat. This species resides in isolated locations and in upstream, brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. In this study, we investigated the population structure and reproductive biology of D. japonicus in the Kita River, Japan. The distribution, sex ratio, breeding season, and fecundity were assessed at bimonthly intervals during spring low-tide periods from May 2001 to November 2008 and from November 2014 to January 2016 for approximately nine years. A total of 3525 crabs were collected during the sampling period: 1806 (51.2%) males, 1240 (35.2%) non-ovigerous females, and 479 (13.6%) ovigerous females. The overall sex ratio (1:0.95) did not differ significantly from the expected 1:1 ratio. The mean maximum density was 26.1 and 36.5 indiv./m2 for the first and second sampling periods, respectively, in the sampling station 5.2 km from the Kita River mouth, and all individuals were typically found approximately 4.4–6.8 km (13.2 ± 7.8 indiv./m2) from the Kita River mouth. Carapace width (CW) ranged from 2.6 to 13.5 mm in males and from 2.8 to 13.4 mm in females and was significantly different between the two sexes (p < 0.05). Ovigerous females were found almost throughout the entire sampling period, with breeding peaks between July and September. The smallest ovigerous female had a CW of 3.9 mm. The seasonal frequency distribution suggested the continuous recruitment of young juveniles (CW < 3.9 mm) throughout the year, with peaks from September to November. The mean fecundity was 1008.3 ± 183.1 (8.3 ± 1.6 mm) eggs. Egg number in relation to CW was calculated by the formula egg number (EN) = 110.36 × CW + 90.96 (R2 = 0.948, n = 41, p < 0.0001). Regression analysis showed that fecundity was closely associated with female CW. Our results indicate that the performance of reproductive biology depends not only on continuous breeding but also on recruitment throughout the year in our study area.

Morphological Variability Among Broods of First-Stage Blue Crab (Callinectes sapidus) Zoeae.

External morphology has been shown to influence predation and locomotion of decapod larvae and is, therefore, directly related to their ability to survive and disperse. The first goal of this study was to characterize first-stage blue crab zoeal morphology and its variability across larval broods to test whether inter-brood differences in morphology exist. The second was to identify possible correlations between maternal characteristics and zoeal morphology. The offspring of 21 individuals were hatched in the laboratory, photographed, and measured. Zoeae exhibited substantial variability, with all metrics showing significant inter-brood differences. The greatest variability was seen in the zoeal abdomen, rostrum, and dorsal spine length. A principal component analysis showed no distinct clustering of broods, with variation generally driven by larger zoeae. Using observed morphology, models of drag induced by swimming and sinking also showed significant inter-brood differences, with a maximum twofold difference across broods. In contrast to trends in other decapod taxa, maternal characteristics (female carapace width and mass and egg sponge volume and mass) are not significant predictors of zoeal morphology. These results suggest that brood effects are present across a wide range of morphological characteristics and that future experiments involving Callinectes sapidus morphology or its functionality should explicitly account for inter-brood variation. Additionally, inter-brood morphological differences may result in differential predation mortality and locomotory abilities among broods.

Experimental evidence for the genetic benefits of female mate choice in the monandrous wolf spider Pardosa astrigera

Material and/or genetic benefits are hypothesized to be the main drivers of female mate choice. Research on female mate choice has mainly focused on polyandrous species and has seldom considered monandrous species. Given the absence of postcopulatory mate choice in monandrous females, we predicted that precopulatory mate choice is important for monandrous species. Using the wolf spider Pardosa astrigera as a model monandrous species, we compared mating, reproductive output and offspring fitness between females with preferred mates (mates that were accepted on the first exposure) and females with nonpreferred mates (mates that were rejected on the first exposure but were induced to mate on the second exposure). Our results showed that the mating duration, latency to egg laying and to egg hatching, fecundity and egg hatching rate did not differ significantly between females with preferred versus nonpreferred mates. In contrast, female and male development time was significantly shorter and female carapace width was significantly greater for offspring of females with preferred versus nonpreferred mates. In addition, survival from egg hatching to maturity was twice as high for offspring of females with preferred mates. These results indicate that female mate choice by the monandrous P. astrigera provides genetic rather than material benefits.

Population structure, recruitment, and mortality of the freshwater crab Dilocarcinus pagei Stimpson, 1861 (Brachyura, Trichodactylidae) in Southeastern Brazil

Freshwater crabs of the family Trichodactylidae are widely distributed in major river basins of the South American continent. The population structure of one species, Dilocarcinus pagei, was analyzed in an artificial reservoir in Southeastern Brazil, recording data on the sex ratio, recruitment, and mortality. A total of 1339 crabs were collected and included 804 males and 535 females (3 ovigerous and 4 with hatchlings); the sex ratio was 1:0.61 (males: females). Two modes of male and female carapace width (CW) were recorded, with means of 14.4 mm (n = 407) and 38.9 mm (n = 394) for males and 17.9 mm CW (n = 269) and 39.2 mm (n = 267) for females. The mean size of males (CW = 26.6 ± 13.8 mm) was significantly larger than that of females (CW = 28.5 ± 12.8 mm). The data indicated that recruitment occurs in summer (January–March), with the reproductive period in spring (October–December), periods with the highest rainfall and temperature values in the region. Reproduction leads to the death of the parents, influencing the sex ratio, which oscillates mainly during the reproductive period.

Reproductive traits of the symbiotic pea crab Austinotheresangelicus (Crustacea, Pinnotheridae) living in Saccostreapalmula (Bivalvia, Ostreidae), Pacific coast of Costa Rica.

Pea crabs of the family Pinnotheridae exhibit a symbiotic life style and live associated with a variety of different marine organisms, especially bivalves. Despite the fact that pea crabs can cause serious problems in bivalve aquaculture, the available information about the ecology of these crabs from Central America is extremely limited. Therefore, the present study aimed to describe different reproductive features of the pinnotherid crab Austinotheres angelicus associated with the oyster Saccostrea palmula in the Golfo de Nicoya, Pacific coast of Costa Rica. Monthly sampling was conducted from April to December 2012. Average carapace width (CW) of the 47 analyzed ovigerous females was 7.62 mm. The species produced on average 2677 ± 1754 recently -extruded embryos with an average volume of 0.020 ± 0.003 mm3; embryo volume increased during embryogenesis by 21%, but did not vary significantly between developmental stages. Brood mass volume varied greatly (between 11.7 and 236.7 mm3), and increased significantly with female CW. Females invested on average 76.7% (minimum: 21.7%; maximum: 162.8%) of their body weight in brood production, which confirms a substantially higher energy allocation for embryo production in pinnotherid crabs compared to free-living decapods.

Current fishing practices may induce low risk of sperm limitation in female swimming crab Portunus trituberculatus in the East China Sea

Potential sperm limitation of the swimming crab Portunus trituberculatus was exam- ined during the reproductive season from September 2006 to April 2007 in the East China Sea. We documented developmental variations between the spermatheca and ovary and distinguished these into 5 stages. We counted the number of stored sperm in paired spermathecae and found that more than 50% of sperm initially received during mating disappeared as the sperm plug degenerated; around 1.70 × 10 8 were used for final fertilization, and there was significant correla- tion between the final number of stored sperm and female carapace width. Lastly, using knowl- edge of the reproductive characteristics of P. trituberculatus, we calculated potential sperm:egg ratios of 221:1 or 153:1 for the first brood, and 55:1 or 38:1 for lifetime broods—either from the per- spective of a fishery resource assessment or from the perspective of seed production. From com- parison to sperm:egg ratios of Callinectes sapidus (for lifetime broods this ranges from 10:1 to 42:1), we can infer that female P. trituberculatus in the East China Sea may be at low risk of sperm limitation under current fishing practices. This may be the result of greater fishing mortality of females, causing an increase in the operational sex ratio. The present study improves our knowl- edge of sperm limitation in brachyurans as fishing management in China is non-selective, which differs from other exploited decapod crustacean species around the world.

Reproductive Allometry ofPodocnemis expansa(Testudines: Podocnemididae) in Southern Brazilian Amazon

Podocnemis expansa is the largest freshwater turtle in South America and exhibits a complex reproductive behavior. Females lay eggs in sandy banks formed during the dry season. Nesting habitat can influence hatching success and sex determination. In some turtle species, female body size is crucial to determine reproductive parameters such as clutch size and shape. In this study, we investigate allometric relationships between female body size and their tracks, and clutch characteristics and nest shape in sandy beaches along the Javaés River, southern Brazilian Amazon. Our results indicate that female body size can be estimated based on tracks. Larger females leave larger foot tracks in the sand and have larger clutch sizes with larger clutch mass than smaller females. Female carapace width and body mass can be considered reliable variables to estimate clutch size and total clutch mass for the species. Larger females should be protected because they can be responsible for most annual clutch production.Podocnemis expansa é o maior quelônio de água doce da América do Sul, apresentando um comportamento reprodutivo complexo. Essa espécie nidifica em bancos arenosos formados durante as vazantes dos rios da Amazônia. As características do ambiente de nidificação podem influenciar o sucesso reprodutivo e o sexo dos filhotes. Alguns trabalhos já demonstraram que o tamanho corporal da fêmea é determinante para as condições da ninhada (quantidade e tamanho dos ovos) e nas dimensões dos ninhos (profundidade e diâmetro) em algumas espécies de quelônios. O presente estudo investigou as relações alométricas entre o tamanho corpóreo da fêmea, seus rastros, as variáveis da ninhada e a forma dos ninhos em ambiente natural em uma praia do rio Javaés, na Amazônia Brasileira. Foi observado que o tamanho corpóreo da fêmea de P. expansa pode ser estimado em função do seu rastro. Fêmeas maiores deixam rastros maiores na areia, além de produzirem mais ovos (tamanho da ninhada) e com maior massa (massa da ninhada) do que fêmeas menores. A largura da carapaça e a massa da fêmea podem ser consideradas variáveis confiáveis para estimar o tamanho e a massa da ninhada dessa espécie. A proteção de fêmeas de maior tamanho deveria ser priorizada, já que podem ser responsáveis por grande parte da produção anual de ovos.

Biological characteristics of parasitic Nepinnotheres novaezelandiae within a Perna canaliculus farm

Pea crabs are commercially significant parasites in the aquaculture production of bivalves in many parts of the world. However, there is scant information available on the biology of these important parasites in aquaculture. The population structure, sex ratio, and breeding status were determined for the pea crab Nepinnotheres novaezelandiae residing in a typical green-lipped mussel Perna canaliculus farm in New Zealand. Of the 324 crabs randomly sampled, there were significantly more female (82.4%) than male (17.6%) crabs found. The vast majority of crabs (87.0%) were sexually mature and of these, females comprised 86.4% and males 13.6%. However, the sex ratio of immature crabs was relatively even, suggesting that male crabs may have higher mortality while searching for mates. Crab size was highly variable, indicating that recruitment to mussels in the farm was continuous. Carapace width ranged from 4.00 to 11.5 mm, with males tending to be smaller with a mean (±SE) carapace width of 6.31 ± 0.16 mm versus females with a carapace width of 8.03 ± 0.06 mm. The crabs did not show any preference for parasitizing mussels of different sexes. Despite the fact that the mussels were only 10 mo old, most female crabs were sexually mature (Stage V) and 89.3% were gravid. The mean (±SE) clutch size was 2592 ± 579 and clutch size was directly associated with female carapace width. The mussel farm pea crab population was estimated at 126390 ± 14144 individuals, including 93000 gravid females carrying a total of over 241 million eggs. Overall, the results show that pea crabs rapidly colonize farmed mussels and mature quickly to establish a significant breeding population within the mussel farm, with larval output capable of infecting nearby mussel farms as well as wild populations of bivalves.

The early life history of Chiromantes ortmanni (Crosnier, 1965) (Decapoda: Brachyura: Sesarmidae): morphology of larval and juvenile stages

The early life history of the sesarmid crab Chiromantes ortmanni (Crosnier, 1965) was studied at constant laboratoryconditions, and the complete larval and early juvenile development are described. Chiromantes ortmanni showsintraspecific variability in the pattern of larval development, which typically includes 5 or, less frequently, 6 zoeal stagespreceding the megalopa. The regular pathway (with 5 zoeal stages) required ca 18–20 days. During this time span, zoealsize (carapace length) increased by a factor of 2.2 from 0.33 to 0.73 mm, while biomass (measured as zoeal dry mass andcontents of carbon, nitrogen and hydrogen) showed an 8-fold increment. The megalopa moulted after 10–12 days to thefirst juvenile crab stage, the total larval development from hatching to metamorphosis taking approximately one month(or ca. 4 days longer in larvae passing through an additional zoeal stage). First egg-laying was observed 8.5 months later,at a female carapace width of 14.4 mm. After an embryonic development time of 26–27 days, a total of 3,470 larvaehatched during two subsequent nights. Hence, the minimum generation time (from hatching to first offspring release)comprised slightly more than 10 months. Unlike the regular zoeal stages, the supernumerary stage VI showed atypicalcharacters for Sesarmidae larvae, especially in the setation pattern of the first maxilliped and the segmentation of theendopod of the second maxilliped. Some characteristics presented an intermediate morphology between that of the zoeaV and the megalopa. The first juvenile stage (crab I) is described in detail, while only the most relevant morphologicalchanges and sexual differentiation are highlighted for subsequent crab stages (II–IX). Males and females can bedistinguished from instar V onward, based on sexual dimorphism in the pleopods and the presence of gonopores in thefemales. The morphological characters of all larval stages and of the first juvenile crab are compared with those of other Chiromantes spp.

Fecundity and Egg Diameter of Primiparous and Multiparous Blue Crab Callinectes sapidus (Brachyura: Portunidae) in Mississippi Waters

Blue crabs Callinectes sapidus Rathbun, 1896 support large commercial and recreational fisheries along the Atlantic coast and in the Gulf of Mexico (GOM). Female blue crabs are traditionally believed to produce one to six broods in their lifetime. However, recent evidence has shown that females have the ability to spawn up to eight broods in a single spawning season, with as many as 18 broods over their lifespan. In this study, fecundity and egg diameter were examined by brood class (primiparous, multiparous) in the spring and summer/fall. Mean carapace width of females was significantly different between brood class and season, with the largest females in the spring. There was a positive relationship between fecundity and carapace width. Although primiparous spring females were the most fecund (3.2 ± 1.5 million eggs), no statistically significant differences in fecundity by brood class and season were found. Loss of eggs occurred during embryonic development; primiparous females lost ∼0.9 million eggs whereas multiparous females lost ∼0.1 million. Egg diameter and carapace width of the female were positively correlated. There was no difference in egg diameter between brood classes, but eggs were 9.9% larger in diameter during the spring than summer/fall. There was an inverse relationship between fecundity and egg diameter. Seasonality appeared to play an important role in the reproductive life history of blue crabs in the northern GOM. Larger crabs and larger eggs in the spring may be related to quality and quantity of available food and temperature conditions for optimal growth.

A Contemporary, Sex‐Limited Change in Body Size of an Estuarine Turtle in Response to Commercial Fishing

Juvenile growth rate and adult body size are important components of life-history strategies because of their direct impact on fitness. The diamondback terrapin (Malaclemys terrapin) is a sexually dimorphic, long-lived turtle inhabiting brackish waters throughout the Atlantic and Gulf coasts of the United States. In parts of its range, terrapins face anthropogenically imposed mortality: juveniles of both sexes inadvertently enter commercial crab traps and drown. For adult females, the carapace eventually grows large enough that they cannot enter traps, whereas males almost never reach that critical size. We compared age structure, carapace dimensions, growth curves, and indices of sexual dimorphism for a Chesapeake Bay population of terrapins (where mortality of turtles is high due to crab traps) with contemporary terrapins from Long Island Sound and museum specimens from Chesapeake Bay (neither group subject to commercial crab traps). We also calculated the allochronic and synchronic rates of evolutionary change (haldanes) for males and females to measure the rate of trait change in a population or between populations, respectively. We found a dramatic shift to a younger male age structure, a decrease in the length of time to terminal female carapace size, a 15% increase in female carapace width, and an increase in sexual dimorphism in Chesapeake Bay. In a new twist, our results implicate a fishery in the selective increase in size of a reptilian bycatch species. These sex-specific changes in life history and demography have implications for population viability that need to be considered when addressing conservation of this threatened turtle.

Life history of the pea crab, Pinnotheres sinensis, in terms of infestation in the bivalve mollusc, Septifer virgatus

The inter-relationship between the pea crab Pinnotheres sinensis and its bivalve host Septifer virgatus was studied from July 2002 to December 2004. The infested bivalve generally contained a single crab (72.4–94.7%), but multiple infestation was also observed in some cases (5.3–27.6%). Seasonal fluctuations in the prevalence rate, sex ratio and ovigerous rate were examined. The prevalence rate and sex ratio increased in autumn and decreased from spring to summer. By contrast, the rate of the ovigerous female increased in summer and decreased in autumn. The carapace width of females was larger than that of males, and seasonal fluctuation in the carapace width was observed in the female crabs. All the females had a soft carapace whereas most males had a hard carapace. No females were observed outside the host, though a small number of males were observed outside it. Mating probably took place inside the host where females remained stationary, with males visiting different bivalves as well as spending much time outside the bivalves.

MORPHOLOGICAL MATURITY OF THE KNOBBED SPIDER CRAB, LEUROCYCLUS TUBERCULOSUS (H. MILNE EDWARDS & LUCAS, 1842) (BRACHYURA, MAJIDAE) IN THE NORTHERN PATAGONIAN GULFS

Sexual maturation in brachyurans has three different components: physiological, morphological, and functional. The second is visualized by examining changes in the morphometric relationships between some dimensions of the organs involved in mating and &gg incubation, relative to a standard measure of size. Aiming to establish the size at morphological maturity for the Patagonian knobbed spider crab, Leurocyclus tuberculosas, a morphometric analysis was conducted on specimens sampled in the northern Patagonian gulfs (41?-43?S). Discontinuities were detected in In transformed relationships of abdomen width on carapace width of females, and right chela length on carapace width of males. For females, estimated CWmorph50% (carapace width at which 50% of the individuals attains morphometric maturity) was 47.9 mm, and CW of the smallest ovigerous female observed in the samples was 42.7 mm. For males, a change in the growth rate of ln(ChL) relative to ln(CW) was detected at 48.9 mm CW.

Peculiarities of reproductive biology and larval development of the red king crab Paralithodes camtschaticus in Peter the Great Bay, Sea of Japan

Based on materials from trawling (2002–2005) and plankton (2004–2006) surveys, some problems of the reproduction biology of the red king crab Paralithodes camtschaticus (Tilesius, 1815) population from Peter the Great Bay are considered. It was shown that the width of the carapace varied from 105 to 190 mm in female red king crabs with eggs; 50% of the females reached maturity with a carapace width of 112.8 mm. The average individual absolute fecundity of females was 200000 (114000–296000) eggs. A direct linear correlation between fecundity and female carapace width was recorded. The zoeas I–IV of the red king crab occurred in the plankton from the middle of April up to the end of the second decade of May at water temperatures from 2.8 up to 9.3°C. The periods of larval occurrence in plankton in various years correlated with the water temperature, with a temperature decrease, the duration of the pelagic period increased. No direct correlation was revealed between the phytoplankton bloom and larval release. The density of red king crab larvae in Peter the Great Bay did not exceed 0.02–13.3 spec./m3. The maximum concentration of zoeas was recorded in the central part of Ussuriysky Bay.

Potential Fertility and Egg Development (Volume, Water, Lipid, and Fatty Acid Content) through Embryogenesis of Uca Rapax (Decapoda: Brachyura: Ocypodidae)

We examined potential fertility, egg volume, and water, lipid, and fatty acid content through embryogenesis in a population of female U. rapax from Sebastian Inlet, Florida. Carapace width (CW) ranged from 10.80 to 20.09 mm (N = 184), and each female carried 5000 to 30,000 eggs in the last stage of development. Female CW was found to be a good predictor of the number of eggs in the later stage of development (potential fertility = 7.908 CW2.7655, R2 = 0.749). Egg volume increases (from 0.0079 to 0.0134 mm3) was mildly correlated (r = 0.79) with an increase in egg water content (from 60 to 69%). Egg lipid and fatty acid content decreased through embryogenesis, due to its importance as energy source. The most consumed fatty acids were the monounsaturated (97.81 μg . mg dw−1) followed by the saturated (64.34 μg · mg dw−1) and polyunsaturated (38.69 μg · mg dw−1). Fatty acids 16:0, 18:2n-6, 16:1n-7, and 18:2n-6 are consumed preferentially (39.91, 38.45, 29.4 and 23.93 μg · mg dw−1, respectively), while essential polyunsaturated fatty acids, particularly docosahexaenoic acid (22:6n-3) and eicosapentaenoic acid (20:5n-3), are conserved. Egg fatty acid profile also reflects diet and habitat of adults. A medium-low EPA/DHA ratio suggests U. rapax occupies a medium trophic level. The low ratio (18:1n-7/18:1n-9) and high percentages of 18:1n-9 fatty acid (18%) and essential C18 and C20 polyunsaturated fatty acids (19-23%) suggests adults are omnivores consuming primary producers (like algae and mangrove leaves) and small invertebrates. The high percentage of odd-numbered fatty acids (above 3-3.5%) also suggests scavenger/detritivore behaviour.

Reproductive Ecology of the Terrapene carolina carolina (Eastern Box Turtle) in Central Virginia

The reproductive ecology of Terrapene carolina carolina (Eastern Box Turtle) was studied in an 11-ha woods in Lynchburg, VA. Estimated population demographics included a population size of 176 turtles with a 1:1 male to female sex ratio, population density of 16 turtles/ha, mean clutch size of 3.15 eggs, and a proportion of adult females gravid per year of 0.405. Reproductive output was 112 eggs per year. A positive significant relationship existed between female carapace width and clutch size, as well as female shell height and clutch size. However, no significant relationship existed between female carapace length (CL) and clutch size. When mean clutch size was compared to those of other investigators of T. c. carolina, a slight positive correlation with latitude was indicated, though it was not statistically significant. Mean female CL and clutch size in a Long Island population were both significantly larger than the means from the Virginia population.

Sex ratio, and probability of sexual maturity of females at size, of the blue swimmer crab, Portunus pelagicus Linneaus, off southern Australia

Although the blue swimmer crab, Portunus pelagicus, supports a commercial fishery in South Australia, with an annual landed value of about A$2 million, little information is available on its biology in this region, and this has hindered the development of strategies for effectively managing the fishery. We used generalized linear models to examine the sex ratio of males and females and the probability of sexual maturity of females at size, based on original commercial catch data collected in a fishery monitoring project. Specifically, we modeled temporal changes in the sex ratio as a cosine function and the probability of sexual maturity of females at size as a logistic function through a logit transformation. We reparameterized both equations, and gave formulae for calculating the standard errors of the estimates of reparameterized parameters characterizing such temporal changes in sex ratio, sizes at x% sexual maturity, the mean and variance of the size of females at sexual maturity. The sex ratio of male crabs in commercial catches decreased from a maximum on 3 February to a minimum on 2 July, and then increased from the minimum to the next maximum on 3 February for another cycle. Some fishers caught proportionally more males (which have larger sizes than females) than others. The sex ratio of male blue swimmer crabs was related to their condition upon capture: dead (killed by sea lice) crabs had a higher proportion of males than live (commercially usable) ones, which in turn had a higher proportion of males than soft-shelled (moulted) ones. The sex ratio of males increased with water depth from January to September and decreased with water depth from October to December. The sex ratio of males increased with carapace width. Finally, the carapace width of females at 50% maturity was 58.5 (±1.0) mm, and that at 95% maturity was 66.3 (±1.9) mm; the mean and variance of the carapace width of females at sexual maturity were 58.5 (±1.0) mm and 22.9 (±9.0) mm2. Therefore, the current legal minimum carapace width of 110 mm in the commercial fishery allows most mature female crabs to spawn before attaining the legal size for commercial fishing.

Biology and abundance of Cancer bellianus (Decapoda, Brachyura) around the Azores

During 1997, exploratory cruises were conducted to study deep-water crabs south of Pico and São Jorge islands in the Azores archipelago. Baited traps were set at depths of 200–1000 m. The target species were the crabs Chaceon affinis and Cancer bellianus . The latter was the prevalent species shallower than 700 m, a total of 462 (247 males and 215 females) being caught at depths ranging from 200–700 m on rocky substrata. The catch rate of females was higher in shallow water (200–400 m) and that of males higher in deeper water (400–600 m). Sizes ranged from 45–218 mm carapace width (CW). Ovigerous females were not found, and possible reasons for this are advanced. An annual reproductive cycle is outlined. Size at first maturity was not estimated directly, but the observed minimum carapace width of females with spermatophores on their pleopods (132 mm) is suggested as the size of first maturity. Epizoitic barnacles were observed on the exoskeleton of some animals.

Multiple choice criteria and the dynamics of assortative mating during the first breeding season of female snow crab Chionoecetes opilio (Brachyura, Majidae)

Crab pairs, consisting of a male grasping another crab (the graspee), were collected by divers during the first breeding season of female snow crab Chionoecetes opilio. Different types of graspees were found and were ranked according to their reproductive value to the male. High-value graspees were pubescent females (close to their terminal maturity molt) and nulliparous females (just molted and close to oviposition). Postmolt primiparous females (clean-soft shell and carrying eggs) also mated and were inseminated by males, but they were of less value than pubescent or nulliparous females as there was only a remote chance that the males' stored sperm would be used to fertilize the next egg clutch. Females copulated with up to 6 different males during their first breeding season. Another category of graspees including males and juvenile females provided the grasping male with no fecundity benefit. Pubescent females paired with males up to 13 d before molting. Males grasping the high-value pubescent and nulliparous females were larger, had a harder shell, and were missing fewer limbs than the males grasping low-value primiparous females, other males or juvenile females and than the overall population of adult males on the mating grounds assessed by trawl. Size-assortative mating by male chela size and female carapace width occurred in the predominant pubescent pairs. Moreover, males with larger chelae were associated with pubescent females missing fewer limbs or having relatively narrower abdomens. Both traits may influence female survivorship and lifetime fecundity. The complex assortative mating pattern of snow crabs apparently derives from mate choice and male sexual competition in the context of prolonged attractiveness of pubescent females to males.