Mean Carapace Width Research Articles

The Effects of Environmental Variables and Morphometry on Hemocyte Structure in the Hemolymph of Portunid Crab, Carcinus aestuarii Nardo, 1847 in Çardak Lagoon (Çanakkale Strait)

This study aims to determine the relationship between hemocyte count and hemocyte types with environmental variables and morphometric measurements in Carcinus aestuarii. A total of 240 crabs were seasonally collected in Çardak Lagoon June 2018, October 2018, February 2019, and May 2019. The average carapace length (CL) was 44.66±0.44 mm, the mean carapace width (CW) was 37.71±0.38 mm and the mean weight was 28.49±0.88 g. Crab specimens were anesthetized on ice for 10 min, and 500 µL of hemolymph was collected from the legs of each crab using a 1-mL plastic syringe. After sampling, hemolymph samples were mixed with the anticoagulant, which was applied to a Thoma slide and examined under a microscope at X40 magnification. The total hemocyte count (THC) was calculated as 13.91±8.08x106 (cells/mm3). Differential hemocyte count (DHC) 53.25±0.6% for hyalinocyte, 26.15±0.23% for semi-granulocyte, and 20.6±0.06% for granulocyte and 3 different cell types were observed. The most dominant cell type is hyalinocyte cells.

The Relationship between Population Density and Body Size of the Giant Mountain Crab Indochinamon bhumibol (Naiyanetr, 2001), an Endangered Species of Freshwater Crab from Northeastern Thailand (Potamoidea: Potamidae)

The giant mountain crab (Indochinamon bhumibol) is endemic to Loei Province in north-eastern Thailand. Although, little knowledge is available on the factors affecting population dynamics and individual fitness. This study aimed to investigate the relationship between the population density and body size of the crab. The mark–recapture method was conducted in Phu Ruea National Park (PR, small area) and Phu Luang Wildlife Sanctuary (PL, large area) between February 2018 and January 2019. The crabs inhabited mountain streams at 400–1100 m. The average water depth and width were 0.6 m and 8.3 m, respectively. In total, 879 individuals were caught from PL compared to 583 individuals from PR. Male were more abundant than female in both areas. Male were also larger and heavier, with a mean weight of 145 g, mean carapace width of 76 mm and mean carapace length of 75.7 mm. The average number of crabs caught was higher in the rainy season (66.3 individuals). The crab population was larger in PL (256.7 individuals), which is bigger in size than PR and is located farther from urban areas. The average crab density in PL and PR were 1.7 and 1.6 crabs/m2, respectively. Population density was significantly correlated with body size parameters: body weight (r2 = 0.066, df = 1196, p < 0.001), carapace width (r2 = 0.053, df = 1196, p < 0.001) and carapace length (r2 = 0.067, df = 1196, p < 0.001). The findings of this study suggest that a large area size and high population density are important to the conservation of the giant mountain crab in mountainous forests.

Heavy metal concentration levels and biometric analysis of Liocarcinus depurator from different locations on the western Black Sea coast of Turkey.

The aim of the current work is to examine the concentrations of nine heavy metals such as chromium, nickel, copper, cadmium, zinc, cobalt, iron, lead, and metal (aluminium) in two body parts (carapace and walking legs) of Liocarcinus depurator from different stations (İlyas bey, Cide koyu, Anadolu feneri, igneada) in the western Black Sea coast of Turkey. And this study was carried out to examine morphological properties of Liocarcinus depurator in the region. The sex ratio (female/male) of 387 samples was calculated as F/M = 1:0.945. The mean carapace length and width were measured as 20.41 ± 2.41mm and 25.10 ± 2.78mm for female and 25.49 ± 3.33mm and 32.32 ± 4.50mm for male individually. The mean weight of crabs was measured as 4.09 ± 1.37g for females and 8.33 ± 3.35g for males. The samples were investigated trace metals by inductively coupled plasma-optical emission spectrometry (ICP-OES). Ranges over trace metals in all samples of L. depurator as follows: Cr 0.6-1.5, Mn 21-130, Cu 8-37, Zn 6-40, Cd 0.2-1.5, Pb 0.1-3.6, Co 0.1-1.1, Fe 22-160, and Ni 0.6-1mg/kg wet wt. The walking legs and carapace/exoskeleton of female and male crabs were analyzed and contained various concentrations of Pb, Co, Ni, Cr, Cd, Fe, Cu, Zn, and Mn elements. The order of the heavy metal in all samples of L. depurator is shown as Fe > Cu > Mn > Zn > Cr > Cr > Ni > Cd > Pb > Co. In this research, metal levels of the crab samples compared between female and male and found highest mean metal concentrations in the station number 3 (Anadolu feneri) that the Al concentration in the carapace of female was 295.0mg/kg wet wt and in the walking legs was 306.67mg/kg wet wt, in the carapace of male was 264.4mg/kg wet wt, and in the walking legs was 162.61mg/kg wet wt in station number 3 (Anadolu feneri). The purpose of this work is to analyze the metal composition of this type of crab, which is abundant in the Black Sea region and is not planned to be attached to fisherman's nets, to evaluate whether it will be useful or not.

Freshwater crabs (Decapoda: Pseudothelphusidae) increase rates of leaf breakdown in a neotropical headwater stream

Abstract Freshwater crabs are the largest macroconsumers in many neotropical headwater streams, but few studies have examined their roles in ecosystem processes such as leaf litter breakdown. As omnivorous macroconsumers, freshwater crabs affect multiple trophic levels. They may directly increase leaf breakdown through fragmentation and consumption or indirectly decrease breakdown by consuming other macroinvertebrates, including shredders and detritivores. In a headwater stream in Monteverde, Costa Rica, we conducted an in‐stream experiment with 40 enclosures to quantify the effects of pseudothelphusid crabs on both leaf breakdown and macroinvertebrate colonisation of leaves. Half of the enclosures were randomly selected to contain two crabs (mean carapace width = 30 mm) and half were controls without crabs. We sampled mixed leaf packs from the enclosures on days 11, 19, 28, 34, and 42. We found the leaves of one species (Koanophyllon pittieri) almost completely decomposed by day 28 in both treatments (crab versus no crab). The other two leaf species (Meliosma idiopoda, Quercus brenesii) composed the remaining leaf mass at the end of the experiment. At 42 days, enclosures with crabs had faster rates of leaf breakdown than those without crabs (with crabs: k = −0.020; without crabs: k = −0.016; p = 0.034). This suggests that the magnitude of direct leaf breakdown by crabs, due to fragmentation, consumption, or manipulation of leaves, was greater than any indirect effects on leaf breakdown via crab consumption of other leaf‐consuming species. Macroinvertebrate composition based on taxa abundances or biomasses did not significantly differ between treatments (ANOSIM; p = 0.73 and p = 0.65, respectively). Shredder and detritivore abundances and biomasses increased significantly through time (ANOVA; p ≤ 0.001), but there was no evidence of an effect of crab presence (p > 0.2), nor were there significant interactions between crab presence and time (p > 0.3). This is one of the first studies to quantify the effects of pseudothelphusid freshwater crabs on leaf breakdown rates. Our results suggest that these crabs can play a significant role in detrital processing in neotropical headwater streams. This study has also demonstrated that short‐term enclosure experiments are useful in measuring in‐stream effects of crab activity on leaf breakdown.

Population structure and dynamics of the invasive crab Charybdis longicollis parasitised by the rhizocephalan Heterosaccus dollfusi along the Mediterranean coast of Turkey

The invasive crab Charybdis longicollis was first reported in Mersin Bay (Mediterranean Sea/Turkey) in 1954, and since the early 1990s, its populations have been heavily parasitised by the alien rhizocephalan Heterosaccus dollfusi. In Antalya Bay, 46.6% of the trawled catch is constituted by C. longicollis. Monthly biomass values fluctuated between 67 kg km−2 (June) and 704 kg km−2 (October), with a mean of 260 kg km−2. The percentage of change in females ranged from 29% in October to 53% in January. The mean carapace width of uninfected crabs was significantly larger in males (35.1 mm) than females (30.6 mm). Male crabs (34.3%) were more heavily parasitised than females (12.1%). The reduction in size of the chela and broadening of the abdomen are two characteristic modifications of infected males. The size at first maturity was estimated at CW = 24.7 mm. Ovigerous females were found all year-round but were more abundant in spring. Male and female individuals of C. longicollis displayed a maximum of three and one modal groups per year, respectively. Natural mortality (M) was estimated as 1.1 year−1 for male crabs.

Reproductive biology of blue swimming crab, Portunus segnis (Forskal, 1775) in Yumurtalık Cove, Northeastern Mediterranean, Turkey

Blue swimming crab, Portunus segnis is a Lessepsian migrant into the Mediterranean and little is known about the biology of it in Iskenderun Bay, Northeastern Mediterranean, Turkey. In the present study the sex ratio, gonadal development stages, gonadosomatic index, size at first sexual maturity, and the fecundity of P. segnis were examined. The specimens of P. segnis were collected monthly from July 2014 to June 2015 (except February) with trawl net from the Yumurtalık Cove. The crabs were found throughout the year and were abundant between July to October (74%). Carapace width range of all samples was between 38.1-163.17 mm, and body weight ranged from 3.46-324.36 g. The population sex ratio was obtained Male:Female=0.7:1 which showed more abundant female population. Fifty percent of the female crabs attained sexual maturity when they reached the sized of 115-119.99 mm CW. The ovigerous female crabs ranging between 101.39- 154.03 mm CW can produced 139379 to 2745236 eggs. The mean fecundity of P. segnis was 1070425±580978 eggs with a mean carapace width of 130.04±12.77 mm. In Yumurtalık Cove, breeding season of P. segnis were observed throughout the year, except winter. Further studies are needed for assessing the reproductive biology of blue crabs in other locations of Turkey.

Female reproductive pattern of Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae) in Iskenderun Bay, Eastern Mediterranean

We studied the female reproductive pattern of Callinectes sapidus, which was introduced to the Mediterranean in the 20th century. We assessed female size at first maturity, fecundity, and fecundity relationship to size in Iskenderun Bay, eastern Mediterranean, Turkey. Samples were collected between July 2014 and June 2015 using bottom trawling at depths ranging from 1 to 50 m. A total of 322 crabs were caught of which 308 (95.7%) were females including 116 ovigerous ones. The minimum carapace width of the mature females was 39.1 mm and the mean carapace width 123.8 mm. The carapace width of ovigerous females varied between 95.1 and 144.5 mm, with a mean of 120.3 mm. The highest number of ovigerous females was observed in July and August. Mean fecundity was 1.91 million (667,950–4,669,853) eggs per female. A weak positive linear relationship between fecundity and carapace width was noted, as well as a high correlation with total egg weight. In the eastern Mediterranean, maturity sizes of females were smaller than those in the native region of the species.

Reproductive ecology, spawning potential, and breeding season of blue swimming crab (Portunidae: Portunus pelagicus) in Java Sea, Indonesia

Ernawati T, Sumiono B, Madduppa H. 2017. Reproductive ecology, spawning potential, and breeding season of blue swimming crab (Portunidae: Portunus pelagicus) in Java Sea, Indonesia. Biodiversitas 18: 1705-1713. The blue swimming crab (Portunidae: Portunus pelagicus) is one of the most economically important fisheries species in Indonesia. Little is known about their reproductive ecology and key biological characteristics. This study aimed to investigate population biology and reproductive ecology (Carapace’s width to weight relationship, growth, natural mortality, size at first maturity and at first captured, Spawning Potential Ratio (SPR), and breeding season) of P. pelagicus at six important landing sites around the Java Sea (Jakarta, Cirebon, Demak, Rembang, Sumenep, and Sampit) from January 2014 to January 2015. Monthly data were collected by fishers at each landing sites, with a total of 14,408 individuals being measured. The study found that males were heavier than females and the smallest mean of individuals’ height belonged to Jakarta compared to other locations. The growth parameters varied at the different locations. Crabs could grow up to 100 mm in 10 months with the maximum age being less than three years. The growth rate (K) of more than 1 indicated a fast-growing crustacean with a short lifespan. The lowest carapace width at first capture (Lc) for the BSC was obtained from crabs caught using a bottom gillnet landed in Jakarta, followed by dredged crabs in Cirebon. The mean carapace width at first maturity (Lm) in the Java Sea was 10.6 cm, with the lowest Lm of female crabs being landed in Cirebon and the highest in Sampit. The Spawning Potential Ratio (SPR) ranged from 11% to 24% and the selectivity curve for the BSC fishery at each landing sites is positioned well to the right of the generic maturity curve, except in Demak, suggests that the operation enables almost all crabs to mature and spawn before entering the fishery. The collapsible trap was the most selective gear, with an average catch of 112 mm across at all landing sites, and the least selective was in trawls. Therefore consideration needs to be given to the different gear types used to catch crabs to leave smaller crabs in the water longer to grow to maturity. Considering its fast growth and peak season (February-April and August-October), a short-period is recommended at some sites that have been over-exploited to rebuild a broodstock to support the long-term sustainability of this species.

Sympatric occurrence and population dynamics of Scylla spp. in equatorial climate: Effects of rainfall, temperature and lunar phase

Mud crabs (Scylla spp.) are known to exist sympatrically in the wild. However, information on their population dynamics and the influence of climate parameters and lunar phase, especially along the equatorial region, are limited. Four sampling stations representing three seas (the Strait of Malacca, South China Sea and Sulu Sea) along the equator were selected. Mud crabs were collected using baited traps during spring tides from April 2012 to July 2013. All three Scylla species, S. olivacea, S. tranquebarica and S. paramamosain live in sympatry in the three seas. Scylla olivacea is the most prevalent species in the Strait of Malacca and South China Sea, whereas S. paramamosain dominates the Sulu Sea. The total crab abundance was not affected by rainfall or temperature. The abundance of S. tranquebarica in Strait of Malacca was negatively correlated with temperature and positively correlated with rainfall whereas the abundance of S. paramamosain positively correlated with temperature only at South China Sea. Scylla tranquebarica was the largest in terms of body size and it showed interchanging abundance trends with S. paramamosain. The average body size of S. paramamosain did not differ significantly with that of S. tranquebarica and S. olivacea. This decrease is most likely attributed to overfishing. Significant seasonal fluctuations in mean carapace width were detected in S. tranquebarica and S. paramamosain, but not in S. olivacea. The monthly sex ratio of all three species occasionally fluctuates above the equal sex ratio value. Lunar phase did not affect species abundance, but males and females were significantly heavier during full moon. These findings serve as a baseline of seasonal variation in crab population dynamics that are useful in mud crab fisheries and resource management.

Difference in Body Size and Sexual Dimorphism in the Ogasawara Mitten Crab,Eriocheir ogasawaraensis,and the Japanese Mitten Crab,Eriocheir japonica

To highlight adaptation of an endemic species to an oceanic island environment, adult morphological characteristics and growth patterns were compared between a mitten crab endemic to the Ogasawara Islands ( Eriocheir ogasawaraensis ) and a congener from mainland Japan ( E. japonica ). Mean carapace width of E. ogasawaraensis was nearly 1.6 times larger than that of E. japonica in both sexes. A difference was detected in the carapace length versus carapace width relationship between these two species. Comparing chela propodus height versus carapace width, a sexual difference was detected similarly in both species, but males had only one growth phase in E. ogasawaraensis , whereas males of E. japonica were dimorphic due to two growth phases. The regression line obtained for male E. ogasawaraensis (chela propodus height versus carapace width) was nearly on the extending line of small-phase male E. japonica . Female E. ogasawaraensis had relatively larger chelipeds than female E. japonica . As for ambulatory legs, E. japonica males had relatively longer legs than females, but no sexual difference was detected in E. ogasawaraensis. Eriocheir ogasawaraensis had relatively shorter legs than male E. japonica but longer legs than female E. japonica . Therefore, in E. ogasawaraensis sexual dimorphism was not as differentiated as in E. japonica , and the adult male dimorphism recognized in E. japonica was absent. The large body size of E. ogasawaraensis is consistent with island gigantism that is commonly found in response to a lack of large predators on isolated islands. Evolution of dimorphism can be explained by sexual selection, and the differences between the island and mainland species are presumed to be correlated with differences in the mating behavior and/or environmental factors in their habitats.

Stone Crab Menippe spp. Populations on Louisiana's Nearshore Oil and Gas Platforms: Higher Density and Size at Maturity on a Sand Shoal

AbstractOil and gas platforms are common in the northern Gulf of Mexico. Platforms provide substrate for sessile organisms such as barnacles and oysters that enhance habitat for stone crabs Menippe spp. and other fouling‐associated organisms. In recent years, Louisiana's small nearshore platforms (<15 m) have been subjected to a high rate of removal, but little is known about their relative value as artificial reefs. During 2014, we compared stone crab populations at platforms on and off Ship Shoal in order to evaluate habitat conditions in the two areas. We hypothesized that platforms on the shoal would provide higher quality habitat than those in the surrounding area because the shoal supports higher diversity and abundances of benthic organisms. Stone crab populations were characterized by means of visual counts and by removing subsamples for species identification, sexing, and carapace measurements. Of the 378 stone crabs collected, 368 were Gulf stone crabs M. adina and 10 were Cuban stone crabs M. nodifrons. Stone crabs colonized every platform studied, but densities were higher (mean values: 4.0 crabs/m2 on the shoal versus 1.8 crabs/m2 off the shoal), and carapace width at 50% maturity (CW50) was 27.1 mm larger for crabs on than off the shoal. Mean carapace width, size‐class distribution, and sex ratio of crabs on and off the shoal were not significantly different. Platforms provided substrate for barnacles, which enhanced the structural complexity of platforms and were observed to be prey for stone crabs. Nevertheless, higher stone crab density and CW50 on the shoal suggested that shoal platforms are better habitat types for stone crabs.Received February 23, 2016; accepted January 9, 2017 Published online March 15, 2017

Population structure and morphometric variation in the sand-bubbler crab Scopimera crabricauda (Brachyura: Dotillidae)

In the present study, population ecology and relationships between various morphometric characters of the sand-bubbler crab Scopimera crabricauda from the Persian Gulf (Iran) were studied. Crabs were collected monthly by excavating nine quadrats in high-density areas of open burrows at low, mid and high intertidal levels during spring low tides for one year. A total of 534 crabs was collected, of which 70% were males (and 30% females). Mean carapace width and total weight in both sexes showed significant differences. Crabs with a carapace width ranging from 5 to 7 mm were the dominant crabs in the population. The highest numbers of crabs were found in the higher intertidal area. The mean size of crabs decreased towards the sea. The aggregation of small crabs was found towards sea in female crabs. Juveniles were abundantly found from January to March whereas the sub-adults and adults were mostly found from April to January. The carapace length to carapace width relationship differed between males and females, as did the carapace width and carapace length to total weight relationships. Finally, the relationship between carapace width and weight for both sexes showed that the growth of this species is allometric.

Use of an eel pass by virile crayfish on the lower Shenandoah River.

Fish passage facilities for reservoir dams have been used to restore habitat connectivity within riverine networks by allowing upstream passage for native species. These facilities may also support the spread of invasive species, an unintended consequence and potential downside of upstream passage structures. We documented dam passage of the invasive virile crayfish (Orconectes virilis) at fish ladders designed for upstream passage of American eels (Anguilla rostrata) in the Shenandoah River drainage. Ladder use and upstream passage of 11 virile crayfish occurred from 2007–2014 during periods of low river discharge (<30 m3s–1) and within a wide range of water temperatures from 9.0–28.6 °C. Virile crayfish that used the eel ladders were large adults with a mean carapace length and width of 48.0 mm and 24.1 mm, respectively. Our data demonstrated the use of a species-specific fish ladder by a non-target species, which has conservation and management implications for the spread of aquatic invasive species and upstream passage facilities.

Size at maturity for grooved Tanner crab (Chionoecetes tanneri) along the U.S. west coast (Washington to California)

AbstractWe conducted a multiyear study to examine interannual variability in the mean size (carapace width, mm), maturity size (mm) and depth (m) for grooved Tanner crab (Chionoecetes tanneri (Rathbun, 1893)) along the U.S. west coast. An additional goal was to provide updated estimates of carapace width (mm) at 50% maturity (W50) for male and female grooved Tanner crab and assess changes over time. Randomly selected samples came from trawl surveys undertaken annually by the Northwest Fisheries Science Center at depths of 55 to 1280 m. We used allometric relationships between carapace width (CW) and either abdominal width (AW) (females) or chela length (CL) (males) to determine functional maturity by sex. We evaluated maturity by fitting logistic regression models to proportion mature grooved Tanner crab. W50 varied significantly between males (125.2 mm) and females (89.1 mm) but interannual differences were slight. The annual mean CW were greater for mature males (139.9–143.4 mm) relative to females (98.8–100.4 mm). The average sizes of immature grooved Tanner crab varied between sexes with males (75.7–84.6 mm) larger than females (66.7–71.9 mm). Size frequency distributions indicated little overlap in the size of mature male and female grooved Tanner crab but considerable overlap between immature grooved Tanner crab. The best model expressing complexity in growth incorporated width, sex and maturity stage. Depth ranged from 195–1254 m with the average depth of a mature grooved Tanner crab (females, 737 m; males, 767 m) significantly shallower than an immature (females, 949 m; males, 918 m) grooved Tanner crab.

Preliminary investigation of direct age determination using band counts in the gastric mill of the blue swimmer crab (Portunus pelagicus Linnaeus, 1758) in two salt-water lakes in the Eastern Mediterranean

The blue swimmer crab, Portunus pelagicus (Linnaeus, 1758), is an important component of the crustacean fisheries in Egypt. This fishery occurs mainly in two salt-water lakes in the Eastern Mediterranean, the coastal Lakes Bardaweel and Timsah, which is located about 100 km further south. We investigated for the first time the applicability of using growth band counts in thin sections of two gastric mill ossicles (mesocardiac and zygocardiac) as age indicator in the blue swimmer crab collected from the two lakes. There was no significant difference in band counts in thin sections of the two ossicles, although the zygo-cardiac ossicles were easier to process. Three growth bands were observed in the ossicles suggesting three years as the species life span. Meanwhile, size modal analysis suggested that the longevity of the species in the two lakes is only two years. Mean carapace width (mm) of the first two presumed year-classes obtained from the band counts and size modal analysis ( y 1 72.8 and 76.2 mm and y 2 91.5 and 97.8 mm, respectively) were not significantly different in Lake Timsah. In Lake Bardaweel, however, the mean size observed at the first two years was different ( y 1 78.5 and 102.2 mm and y 2 94.5 and 128.0 mm for the band count and size modal analysis, respectively). Sex-specific size-at-band counts (estimated age) was demonstrated for the species in both lakes. The models were fitted by power equations and there was no significant difference in the growth models between sexes in the two lakes. Further validation needs to be done to confirm the annual deposition of the growth bands before using the results on a routine basis.

An investigation on some biological and reproduction characteristics ofEriphia verrucosa (Forskål, 1775) in the South Black Sea (Turkey)

In this study, a total of 1360 specimens of Eriphia verrucosa were collected from the South Black Sea region of Turkey between February 2012 and January 2013 to determine their biological and reproductive characteristics. The overall sex ratio of all individuals was calculated as 1:0.42 (M/F). The mean carapace width was determined as 6.76, 5.57, and 5.62 cm for males, nonovigerous, and ovigerous females, respectively. The minimum and maximum weight was recorded as 4.07 and 301.4 g for both sexes. The highest correlation between morphological characteristics was determined for carapace length and crab weight in nonovigerous females (R2 = 0.973; N = 317). The percentage of ovigerous females was 6.25% and they were observed only between May 2012 and August 2012. The mean fecundity was calculated as 89,129 ± 8005 eggs. The egg diameter ranged from 499.0 to 701.7 µm with a mean value of 546.36 ± 18.62 µm for stage I, 606.92 ± 15.92 µm for stage II, and 570.96 ± 9.22 µm for stage III.

Upstream dispersal of an invasive crayfish aided by a fish passage facility

Fish passage facilities for reservoir dams have been used to restore habitat connectivity within riverine networks by allowing upstream passage for native species. These facilities may also support the spread of invasive species, an unintended consequence and potential downside of upstream passage structures. We documented dam passage of the invasive virile crayfish, Orconectes virilis (Hagen, 1870), at fish ladders designed for upstream passage of American eels, Anguilla rostrata (Lesueur, 1817), in the Shenandoah River drainage, USA. Ladder use and upstream passage of 11 virile crayfish occurred from 2007–2014 during periods of low river discharge (<30 m 3 s –1 ) and within a wide range of water temperatures from 9.0–28.6 °C. Virile crayfish that used the eel ladders were large adults with a mean carapace length and width of 48.0 mm and 24.1 mm, respectively. Our data demonstrated the use of species-specific fish ladders by a non-target non-native species, which has conservation and management implications for the spread of aquatic invasive species and upstream passage facilities. Specifically, managers should consider implementing long-term monitoring of fish passage facilities with emphasis on detection of invasive species, as well as methods to reduce or eliminate passage of invasive species.

Occurrence of first crab instars of the Atlantic ghost crabOcypode quadrata(Decapoda: Brachyura: Ocypodidae) along the coast of Maine, U.S.A.

Adult populations of Ocypode quadrata have not been reported north of Cape Cod, Massachusetts, but their megalopae, which invade sandy beach habitats, have been recovered recently from the coasts of Massachusetts and Maine. Two megalopa specimens were reported from Maine beaches at Kennebunkport and Kennebunk in 2012. More recently in September 2014, a specimen was collected from Pemaquid Beach, Bristol, Maine, ~ 96 km north of the Kennebunkport-Kennebunk region. Herein, we also report the occurrence of three specimens of first crab instars from Goose Rocks Beach, Kennebunkport, collected on October 2–3, 2014. These juvenile crabs were found slightly above the tide line of the previous high tide, where they were preserved and measured (mean carapace width x carapace length = 6.34 ± 0.38 mm x 5.64 ± 0.34 mm; mean carapace width/carapace length ratio = 1.13). This is the first evidence for megalopa to first crab metamorphosis of ghost crabs in the cold waters beyond Cape Cod. Conformation of survival of early crab instars of O. quadrata, a primarily southern latitude brachyuran, to adulthood in Gulf of Maine waters requires further collections and experimentation.

Reproductive biology of Hepatus pudibundus (Crustacea: Brachyura), the most abundant crab on the southeastern Brazilian coast

This study analyzed the size at sexual maturity and reproductive period of populations of Hepatus pudibundus in three bays on the northern coast of Sao Paulo, Brazil. Crabs were collected monthly and the bottom-water temperature was measured at each collection point. The animals were sexed, measured for carapace width (CW), and their gonadal stages were determined. A total of 8,674 specimens were collected (2,435 males and 6,239 females). Adult males showed the highest mean CW; the size at maturity for both sexes was 32.5 mm CW. Reproduction was continuous and peaked in spring and summer, because of the greater availability of plankton food for the larvae. This pattern is typical in tropical and subtropical regions, unlike the seasonal reproduction found in temperate regions. Reproductive activity of females was not significantly correlated with bottom-water temperatures. Immatures and individuals in all stages of gonadal development were found throughout the sampling period and at all depths, probably because the species completes its entire reproductive cycle in that area.

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.