Swimming Crab Charybdis Research Articles

Biological aspects of silky shark Carcharhinus falciformis in the eastern Arabian Sea

Reproduction, diet and growth of silky shark Carcharhinus falciformis in the eastern Arabian Sea are described based on 473 specimens collected from the gillnet-cum-longline landings at the Cochin fisheries harbour during 2012–2014. The reproductive biology of 215 males and 258 females was examined while 113 stomachs were sampled to study the diet. The von Bertalanffy growth parameters estimated using length-based models were asymptotic length (L∞) = 309.80 cm, growth coefficient (K) = 0.10 year−1 and age at zero length (t0) = −2.398 year. The sex ratio was significantly skewed to females. Seasonality in reproduction was not evident and in males, sexual maturity was attained at 201–223 cm total length (LT) with the size at maturity (LT50) occurring at 217.0 cm, whereas in females sexual maturity was attained at 224–231 cm LT and LT50 occurs at 226.5 cm. In total 114 embryos, in the length range of 12.2–65.1 cm were recovered from 15 pregnant females. Numbers of embryos in females were in the range of 3–13, averaging 7.6. Silky sharks of the eastern Arabian Sea feed primarily on swimming crab Charybdis smithii, with juveniles feeding principally on swimming crabs, while adults feed on actively swimming prey like squids and teleost fishes. This preliminary information on the reproduction, diet and growth should be useful to identify management strategies for silky sharks in the eastern Arabian Sea.

Stranding and mortality of pelagic crustaceans in the western Indian Ocean

Recent observations of unusual mass stranding and mortality of two Indian Ocean crustacean species, the swimming crabCharybdis smithiiand the mantis shrimpNatosquilla investigatoris, are documented and analysed. Strandings ofC. smithiiwere observed for the first time in the equatorial Indian Ocean, the main area of its pelagic distribution. Strandings of mantis shrimps are reported from throughout the western Indian Ocean; occurrences of mass stranding in the Maldives Archipelago mark an extension of the known range ofN. investigatorisinto the central Indian Ocean. Mortality of crabs probably represents a ‘catastrophic event’. In contrast, mantis shrimp strandings, which were always associated with a sudden increase of its biomass (‘blooms’), are apparently post-reproduction mortalities indicating potential semelparity for this species.

Biological associations of color variation in the Indo-Pacific swimming crab Charybdis hellerii.

A marine biological invasion is a natural process accelerated by human activities, and the crab Charybdis hellerii is an example of a globally widespread invasive species. This study evaluated color variation in C. hellerii and its relationship to the sex, size and sexual maturity of these crabs, and compared the efficiency of a freeware digital image-editing program with a commercially available program. The color of the individuals was analyzed using standardized digital images. The color pattern varied significantly with size; smaller and immature individuals were darker than larger and mature ones. The female abdomen changed in morphology and color with sexual maturity, becoming wider and orange-colored. There was no statistical difference in the color values between males and females and immature males did not show morphological or color differences in their abdomen. This study highlights the possible relationships of the color and physiological state of the reproductive system, which could help in future studies of behavior, avoiding the need to dissect and/or remove individuals from nature for assessment of sexual maturity. The freeware program showed the same efficiency in digital image analysis as a widely known commercial program.

서해 꽃게 자망의 망목 선택성 연구

A series of fishing experiments were carried out in the western coastal waters of Korea from May, 2006 to September, 2007, using gill nets of different mesh sizes (m=101, 121.8, 152.5, 176.8, and 191 mm) to determine the mesh selectivity of gill net for swimming crab, Potunus trituberculatus. The catch species was composed of swimming crab (87%), Thomas's rapa whelk Rapana venosa (5%), arthritic neptune Neptunea cumingi (2%), Japanese swimming crab Charybdis japonica (2%), marbled sole Pleuronectes yokohamae (1%), pen shell Atrina pectinata, ocellate spot skate Okamejei kenojei, and so on. The carapace length (CL) of each swimming crab caught in the experimental nets was measured. Sponge crab (egg-bearing female crab) was appeared from the end of June to August in the coastal waters. The master selection curve was estimated by applying the extended Kitahara's method. The selection curve showed that the gill nets of larger mesh size allowed more crabs of small carapace size to escape. The optimum value (CL/m) was 0.645 and the CL/m was estimated to be 0.301, 0.354, 0.391, 0.422, and 0.450 when the retention probabilities were 0.1, 0.2, 0.3, 0.4 and 0.5, respectively.

First record of Charybdis japonica (Crustacea: Decapoda: Portunidae) in the Mediterranean Sea

The swimming crab Charybdis japonica is recorded for the first time in the Mediterranean Sea. A single adult male specimen was caught in 2006 with gill-net at the entrance of Ancona harbour, on the Adriatic coast of Italy. No other specimens have been found despite extensive surveys of the environs of the port. Unintentional transport by a merchant ship seems the most likely vector of introduction.

On the biology of the Japanese swimming crab Charybdis japonica (Portunidae) in waters of primorye at the northern boundary of their range

Data on the biology of the Japanese swimming crab, such as sexual dimorphism, size and weight structure, sex ratio, allometric growth, and fecundity were obtained in Sukhodol Bay (Ussuri Bay). The maximum carapace width was 116 mm and the largest weight was 340 g in males and 107 mm and 210 g, respectively, in females. The female to male ratio was 1.0: 2.4. The mean number of eggs in a clutch was 571300 (94000–1786000). Molting lasted from August through October, and a mass molt was recorded in August. As compared to crabs of the central part of the range, off the Korean Peninsula, Charybdis japonica in Ussuri Bay had larger size and higher fecundity. The breeding period in Ussuri Bay was slightly shifted from June–August to late June-September. The mass hatching of larvae occurred in July.

Here and There: A Preliminary Note on the Prevalence of an Alien Rhizocephalan Parasite at the Southern and Northern Limits of Its Introduced Range

The Erythrean invasive swimming crab Charybdis longicollis established dense populations in the Levantine Basin of the Mediterranean Sea in the mid 20th century. The crabs were subsequently parasitized by the rhizocephalan Heterosaccus dollfusi , itself an Erythrean alien. In May 2008, the crab populations were sampled at the southern (Israel) and northern (Turkey) limits of its introduced range. The prevalence of infection was 3 times as high, and multiple externae-bearing hosts more than 4 times as many, in Israeli waters as in Turkey. It seems that off the Israeli coast, the water temperature permits the synchronous ontogenetic development of both host and parasite, ensuring the availability of plentiful young, recently-molted, prospective hosts for infection by the short-lived parasite cypris. It is possible that the lower water temperature off Antalya (Turkey) may affect the timing of ontogenetic development of one species or the other, or increase the mortality of infected hosts, resulting in drastically reduced parasite prevalence.

Spatial distribution of the crab larvae (Decapoda: Anomura et Brachyura) in Possyet Bay (Peter the Great Bay of the Sea of Japan) in 2000–2001

The analysis of the data obtained during the plankton surveys in Possyet Bay (Peter the Great Bay of the Sea of Japan) in 2000–2001 is presented. The larvae of eight crab species were registered in the plankton: the red king crab Paralithodes camtschaticus (Tilesius, 1815), the snow (opilio) crab Chionoecetes opilio (Fabricius, 1780), the Arctic lyre crab Hyas coarctatus ursinus (Leach, 1815), the kelp crab Pugettia quadridens (de Haan, 1839), the helmet crab Telmessus cheiragonus (Tilesius, 1815), the Japanese swimming crab Charybdis japonica (A. Milne-Edwards, 1861), the pea crab Pinnixa rathbuni (Sakai, 1934), and the porcelain crab Pachycheles stevensii (Stimpson, 1858). These species belonged to six families: Lithodidae, Atelecyclidae, Majidae, Portunidae, Porcellanidae, and Pinnotheridae. The role of the variability of some of the hydrological factors in the meroplankton larvae development was studied. In May, the crab larvae were found mostly in the open part of the bay. In June, they were transported by the current to the northern part of the bay. In July, they spread uniformly in all the bay areas; however, patchiness was observed. The maximal population density of the crab larvae was registered for July and varied from 6.8 to 23.3 ind. m−3. The crab larvae appeared in the plankton in 2000 and 2001 earlier than for the average season.

The invasion of five alien species in the Delta do Parnaíba Environmental Protection Area, Northeastern Brazil

Marine biological invasions have been regarded as one of the major causes of native biodiversity loss, with shipping and aquaculture being the leading contributors for the introductions of alien species in aquatic ecosystems. In the present study, five aquatic alien species (one mollusk, three crustaceans and one fish species) were detected during dives, shore searches and from the fisheries on the coast of the Delta do Parnaíba Environmental Protection Area, in the States of Piauí and Maranhão, Northeastern Brazil. The species were the bicolor purse-oyster Isognomon bicolor, the whiteleg shrimp Litopenaeus vannamei, the giant river prawn Macrobrachium rosenbergii, the Indo-Pacific swimming crab Charybdis hellerii and, the muzzled blenny Omobranchus punctatus. Ballast water (I. bicolor, C. hellerii, and O. punctatus) and aquaculture activities (L. vannamei and M. rosenbergii) in adjacent areas are the most likely vectors of introduction. All exotic species found have potential impact risks to the environment because they are able to compete against native species for resources (food and habitat). Isognomon bicolor share the same habitat and food items with the native bivalve species of mussels and barnacles. Litopenaeus vannamei share the same habitat and food items with the native penaeids such as the pinkspot shrimp Farfantepenaeus brasiliensis, the Southern brown shrimp Farfantepenaeus subtilis, and the Southern white shrimp Litopenaeus schmitti, and in the past few years L. vannamei was responsible for a viral epidemics in the cultivation tanks that could be transmitted to native penaeid shrimps. Charybdis hellerii is also able to cause impacts on the local fisheries as the species can decrease the populations of native portunid crabs which are commercialized in the studied region. Macrobrachium rosenbergii may be sharing natural resources with the Amazon River prawn Macrobrachium amazonicum. Omobranchus punctatus shares habit with the native redlip blenny Ophioblennius atlanticus and other fishes, such as the frillfin goby Bathigobius soporator Some immediate remedial measures to prevent further introductions from ballast water and shrimp farm ponds should be: (i) to prevent the release of ballast water by ship/vessels in the region; (ii) to reroute all effluent waters from shrimp rearing facilities through an underground or above-ground dry well; (iii) to install adequate sand and gravel filter which will allow passage of water but not livestock; (iv) outdoor shrimp pounds located on floodable land should be diked, and; (v) to promote environmental awareness of those directly involved with ballast water (crews of ship/vessels) and shrimp farms in the region.

The swimming crab Charybdis smithii: distribution, biology and trophic role in the pelagic ecosystem of the western Indian Ocean

Surface “swarms” of the swimming crabs Charybdis smithii are still considered as an unusual phenomenon in the open Indian Ocean, although their dense pelagic aggregations were already reported in waters off the Indian coast and in the northern Arabian Sea. Based on an extensive large-scale data series taken over 45 years, we demonstrate that C. smithii is common in the pelagic provinces of the western Indian Ocean driven by the wind monsoon regime. Swimming crabs are dispersed by the monsoon currents throughout the equatorial Indian Ocean. They aggregate at night in the upper 150-m layer, where their estimated biomass derived from pelagic trawling data can exceed 130 kg km−2. Abundance of C. smithii can reach >15,000 ind. km−2 in July (i.e. the peak of the south-west monsoon), declines by 50-fold in March and is negligible in May. C. smithii is an important prey for more than 30 species of abundant epipelagic top predators. In turn, it feeds on mesopelagic species. This swimming crab is a major species of the intermediate trophic levels and represents a crucial seasonal trophic link in the open ocean ecosystem of the western Indian Ocean. Outbursts in pelagic waters of huge biomasses of ordinarily benthic crustaceans (C. smithii and Natosquilla investigatoris) are a remarkable feature of the Indian Ocean, although similar, but smaller, events are reported in the Pacific and Atlantic Oceans.

Edibility assessment of the swimming crab Charybdis natator (Brachyura: Portunidae) from the Gulf of Suez, Red Sea, Egypt

he portunid crab Charybdis natator exists in the commercial catches of the Gulf of Suez trawlers in a considerable quantity. Although edible worldwide, this crab is hardly known among local consumers. This study aimed to assess the suitability of this crab as food. Examination of the muscle tissues was carried out in terms of biochemical composition (protein, lipids and carbohydrates) and the accumulation of the heavy metals (Cd, Cu, Fe, Pb and Zn). Organoleptic differences among the cooked meat of this species and that of the popular species Portunus pelagicus were tested. Protein constituted over 80% of the muscles dry weight of male and female crab, followed by lipids (7.25-7.79%) and carbohydrates (5.39-6.26%) respectively. Zn was the highest accumulated metal (46.6, 45.4ppm) followed by Cu (24.4, 36.6 ppm), Fe (21.8, 36.2 ppm) and Pb (3.9, 4.6ppm), while Cd was the lowest (0.9ppm) in males and females respectively. Intra-specific and size-based variations in metal uptake were recorded. Test of organoleptic qualities ranked P. pelagicus as higher in all attributes. However, no significant difference was observed in the total acceptability of the two species (P≥ 0.05). The study highlighted the suitability of C. natator as edible, nutritive and safe seafood.

Predation by the swimming crab Charybdis japonica and piscivorous fishes: A major mortality factor in hatchery-reared juvenile Japanese flounder Paralichthys olivaceus released in Mano Bay, Sado Island, Japan

We investigated the impact of predatory crabs and fishes on hatchery-reared juvenile Japanese flounder Paralichthys olivaceus released into a flounder nursery habitat in Mano Bay, Sado Island. In 2001 and 2002, nearly 50,000 reared juveniles (ca. 6.1 cm total length, TL) were released each year, and 68% and 83% of them were estimated to suffer mortality in the first week after release, respectively, for these years. Stomach content analysis of crabs caught in the released area, using a PCR-based technique for detecting Japanese flounder-specific mtDNA, revealed that the swimming crab Charybdis japonica is a significant predator on released flounder. This finding was supported by laboratory observations that the crabs readily preyed on live reared flounder. In addition, through microscopic observations of stomach contents of piscivorous fishes, four species (devil stinger Inimicus japonicus, age-1 Japanese flounder, spotted flathead Cociella crocodila, and bartailed flathead Platycephalus indicus) were identified as predators. Based on stomach content analyses and abundances of these predators, consumption by swimming crabs is estimated to account for 39% and 41% of the loss of released flounder during the first week after release in 2001 and 2002, respectively, whereas consumption by four piscivorous fishes accounted for 25% and 20% of the loss in 2001 and 2002, respectively. Thus, we conclude that predation by crabs and fishes is the major cause of mortality of released flounder shortly after release.

Forage fauna in the diet of three large pelagic fishes (lancetfish, swordfish and yellowfin tuna) in the western equatorial Indian Ocean

Prey composition and resource partitioning were investigated among three large pelagic fish predators, yellowfin tuna ( Thunnus albacares), swordfish ( Xiphias gladius) and lancetfish ( Alepisaurus ferox), in a poorly known oceanic area, the western Indian Ocean. The contents of 380 non-empty stomachs were analysed from specimens caught with longlines during scientific cruises carried out from 2001 to 2003. Diet data were processed by occurrence, mean proportion by number, wet weight, and mean proportion by reconstituted weight. Crustaceans, dominated by the swimming crab Charybdis smithii and the stomatopod Natosquilla investigatoris, were the major food source of lancetfish. Cannibalism was also significant for that species. Yellowfin tunas preyed upon a large diversity of mesopelagic fishes, crustaceans ( C. smithii and crab larvae) and cephalopods (the ommastrephid Sthenoteuthis oualaniensis). Mesopelagic fishes ( Cubiceps pauciradiatus and Diretmoides parini) and cephalopods (mainly S. oualaniensis) were the main prey of swordfish. Diet overlap between swordfish and yellowfin tuna was evidenced by high Morisita–Horn index. But the feeding habits of these three predators differed by foraging depth and prey size, with swordfish feeding at deeper depths and on larger prey than the more epipelagic lancetfish and yellowfin tuna. Using these three predators as biological samplers, the present study provides novel data on micronekton fauna that is poorly documented in the western Indian Ocean: 67 families and 84 species of prey were recovered in the stomach contents, and our results indicate the presence of large resources of pelagic crustaceans that play a primary role in the epipelagic food chain.

The effect of two pot types on entrance rate and entrance behavior of the invasive Japanese swimming crab Charybdis japonica

The behavior of the crab Charybdis japonica towards two pot types was recorded by camera while placed in a tank. One pot was box-shaped with two slit entrances, while the other was dome-shaped with two open funnel entrances. Pots were placed in the tank and the behaviors of single crabs were video recorded for 1.5 h (30 recordings/pot). Crabs attempting to enter the box-shaped pot had trouble getting through the entrances and 37% gave up, while 100% of those reaching the dome-shaped pot's entrances easily entered. The entrance on the dome-shaped pot was 100% efficient while that on the box-shaped pot only caught 66% of the crabs that contacted it.

Observations on the agonistic behavior of the swimming crab Charybdis longicollis Leene infected by the rhizocephalan barnacle Heterosaccus dollfusi Boschma

The effects of the invasive rhizocephalan parasite Heterosaccus dollfusi on the agonistic behavior of the invasive swimming crab Charybdis longicollis were quantitatively analyzed under standardized conditions. The behavior of uninfected male crabs contained more aggressive elements than that of uninfected females. In encounters between infected males, markedly fewer and less aggressive elements were displayed than in encounters between uninfected males, whereas in encounters between infected females, more aggressive elements were displayed than in encounters between uninfected females. It is suggested that the presence of the parasite reduces belligerence in male crabs, possibly to avoid injury and to enhance the life expectancy of host and parasite.

Mass sedimentation of the swimming crab Charybdis smithii (Crustacea: Decapoda) in the deep Arabian Sea

During cruise Meteor 33/1 in the northern Arabian Sea in September/October 1995, large numbers of the portunid crab Charybdis smithii were observed swimming in the open ocean. In a photographic survey at three abyssal stations in the northern Arabian Sea (NAST, WAST, CAST), even higher densities of Charybdis smithii – up to 1 crab m −2 – were found dead on the sea floor. Average sizes of the crabs were around 34–44 mm carapace width, indicating that the animals died prematurely, before returning to the breeding grounds presumable on the shelves of India or Oman. The average weight of the crabs was 10–14 g wet weight. From the photographic quantification it can be deduced that these large food falls represent a significant carbon input of at least 10–30% of the annual flux of POC as measured in sediment traps in this region. The exceptionally high microbial chitinase activity in the surface sediment layers detected at the same stations indicates that this energy is utilized and channelled into the deep-sea benthic food web of the deep Arabian Sea. There are frequent observations of dense Charybdis smithii swarms in the Arabian Sea from different years; however, it is not certain whether such large food falls as observed during M 33/1 are regular seasonal events that repeat each year.

Larval Development of the Swimming Crab Charybdis natator (Crustacea : Brachyura : Portunidae) Reared in the Laboratory

The larval development of the swimming crab Charybdis natator (Herbst, 1789) was studied from first zoea to megalopa under laboratory conditions. Six zoeal stages and one megalopal stage were identified, and detailed descriptions and illustrations are provided for each stage. At an average salinity and temperature of 31±1‰ and 23±1℃, the megalopa was attained 38 days after hatching. Morphologically, the first zoea of C. natator is very similar to those of other species of Charybdis in having lateral spines on the carapace ; three pairs of serrate setae on the posterior margin of the telson furca ; one plus six setae on the endopod of the maxillule ; and five setae on the endopod of the maxilla. The differences between the first zoea and megalopa of C. natator and those of its congeners are discussed.

The distribution and biology of the swimming crab Charybdis smithii McLeay,1838 (Crustacea; Brachyura; Portunidae) in the NW Indian Ocean

On seven cruises with the R.V. Tyro, R.R.S. Discovery and R.V. Malcolm Baldrige in the NW Indian Ocean between 1992 and 1995, the pelagic swimming crab Charybdis smithii was found in great densities during July–August (SW monsoon) and January (NE monsoon). Discrete depth sampling, using RMT1 +8 and Mocness-10 gear, collected the species predominantly in the upper 200 m during night and day. Most of the crabs were concentrated above the thermo- and oxycline, both situated at around 150–200 m. In July–August the stock of crabs showed considerable variation, with maximum values of 1.9–2.4 crabs m −2 (0–500 m, night) foundin the Southern Somali Basin the Omani Basin and in the Central Arabian Sea. The maximum biomass (wet weight) of crabs was 12.7 g m −2 (0–500 m, day) off Somalia and in the Central Arabian Sea during the SW monsoon. In January stocks and biomasses were lower, with maximum values of 0.1 and 2.0, off Somalia at 7°N. The size-frequency distribution of all crabs found during the SW monsoon in the Somali Basin demonstrated the occurrence of smaller instars at the near-coast stations compared with the open ocean stations. During the NE monsoon there was a tendency for nearshore crabs to be larger than offshore. High concentrations of zoea and megalopa larvae of portunid crabs together with juvenile C. smithii were found in neuston samples off Somalia in May. Dense swarms of crabs occurred in the pelagic NW Indian Ocean in June–September (SW Monsoon). In October, crabs began to migrate onshore, where they characteristically formed surface swarms at night. Analysis of combined ship and literature data showed a 1 year life cycle for C. smithii. Aggregation of the crabs on the continental shelf precedes their breeding from about October to January (NE Monsoon). The larvae hatching in shelf waters disperse offshore and, after metamorphosis, form dense pelagic swarms from about July to August (SW monsoon).

Zooplankton and micronekton biomass off Somalia and in the southern Red Sea during the SW monsoon of 1992 and the NE monsoon of 1993

Spatial and seasonal variations in mesozooplankton, macrozooplankton and micronekton biomass distribution were studied in the Somali Basin and the southern Red Sea and Gulf of Aden. Cruises were made in May–June and July–August 1992 during the SW monsoon, and in January–February 1993 during the NE monsoon. Samples were taken in day and night series from stratified layers to depths of 600 or 1000 m, using an RMT1 + 8, combining two nets with mesh size of 0.34 mm and 4.5 mm, respectively. During the SW monsoon the mean zooplankton biomass from RMT1 samples (displacement volume 0–300 m, night) were low in the southern Red Sea and the Gulf of Aden, 14.0–17.5 ml m-2. At 11°N in the Somali Current, where coastal upwelling occurs, the maximum biomass value of 38.0 ml m −2 was recorded. Downstream from the upwelling in the Great Whirl, biomass values were lower, ranging from 21.0 to 35.9 ml m −2. In the Somali Basin south of 5°N the mesozooplankton biomass was lower than in the Somali Current and northern areas. During the NE monsoon large phytoplankton blooms occurred in the southern Red Sea and the Gulf of Aden, and the mean zooplankton biomass almost doubled to 23.9–40.2 ml m −2 compared with the SW monsoon. Primary production in the northern Somali Basin was much higher during the NE monsoon than recorded during earlier studies, and biomass values for the zooplankton therefore were not as low as might be expected. No statistical significant difference was found in the season's mean biomass values. This is remarkable because in the northern Somali Basin the mean phytoplankton carbon production during the NE monsoon was about two-thirds of the production during the SW monsoon. This seeming paradox is probably due to large mesh sizes that did not retain the small size (herbivorous) zooplankton fraction present during the SW monsoon. The mean macrozooplankton and micronekton biomass from RMT8 samples (0–300 m night) in the southern Red Sea, the Gulf of Aden and the Somali Basin showed no significant seasonal difference. However, biomasses of mesopelagic fish and large crustaceans were high in the southern Red Sea during the SW monsoon, and were high in the Somali Current during the NE monsoon, whereas in the northern Somali Basin biomasses remained about the same. Biomasses of large crustaceans in the Gulf of Aden were higher during the NE monsoon. The pelagic swimming crab Charybdis smithii was found during the SW monsoon in the equatorial and northern Somali Basin, attaining high displacements. The species was not found in the Somali upwelling area during this season, whereas during the NE monsoon the highest displacements for C. smithii were recorded. Vertical profiles of biomass from RMTI and RMT8 samples show that zooplankton and micronekton occur in the oxygen minimum zone and that the lowest oxygen concentrations in the sampled depth range (0.11 ml 1 −1) do not seem to hamper diurnal vertical migration.