Impact scenario for the invasive red king crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius, 1815) (Reptantia,Lithodidae) on Norwegian,native, epibenthic prey

Large invasive predators like the king crab, Paralithodes camtschaticus, deserve particular attention due to their potential for catastrophic ecological impact on recipient communities. Conspicuous, epibenthic prey species, such as the slow growing commercial scallop Chlamys islandica, are particularly exposed to the risk of local extinction. A research program integrating experiments and field monitoring is attempting to predict and track the impact of invasive king crab on scallop beds and associated fauna along the north Norwegian coast. The claw gape of the crab shows no limitations in handling the flat-bodied scallop. However, the potential impact of the crab on scallop may depend on the availability of other calcified prey associated with scallop beds, such as the sea star, sea urchin, and blue mussel, all species recorded in the diet of P. camtschaticus. To address this issue, a laboratory experiment on foraging behaviour of P. camtschaticus was conducted. The experimental results show that all size classes of red king crab prefer scallops, but small juveniles and medium sized crabs demonstrate active selection for starfish (Asterias rubens) that equals or surpasses the electivity of the large crab. The selection of sea urchin (Strongylocentrotus droebachiensis) and blue mussel (Mytilus edulis) is slightly positive or neutral for the three crab size classes. These results suggest that scallop beds with a rich associated fauna are less vulnerable to red king crabs predation and possibly more resilient than beds with few associated species. Also, crab size distribution is likely relevant for invasion impact, with increasing abundance of small and medium sized crabs being detrimental for alternative calcified prey associated with scallop beds. Successive stages of crab invasion will see an acceleration of scallop mortality rates associated with (i) decreasing availability of alternative prey, due to protracted predation pressure intensified by recruitment of juvenile crabs, and (ii) increased number of large crabs. Estimates of crab density and intake rates suggest that the accelerated loss rates will eventually endanger scallop beds persistence.     

Fouling community of the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius 1815), in a subarctic fjord of the Barents sea

We examined the species composition of red king crab (Paralithodes camtschaticus) fouling communities in Dolgaya Bay, a small fjord of the Barents Sea, in August 2005 and 2006. In total, there were 13 species observed on 301 crabs collected from water depths of 5–90 m. Barnacles (Balanus crenatus; prevalence 42.9%) and blue mussels (Mytilus edulis; 11.6%) were the most common epibionts, while amphipods (Ischyrocerus commensalis) were the most common symbionts (28.6%). Infestation rates in Dolgaya Bay were different from those in an “open” area of the Barents Sea (Dalnezelenetskaya Bay), probably due to differences in hydrodynamic conditions. Differences in infestation prevalence and intensity were detected neither between male and female crabs nor between crabs collected at 5–35 m versus 90 m depths. Prevalence of common fouling species increased with host size. Amphipods I. commensalis colonized the carapace and limbs in Dolgaya Bay less frequently than in Dalnezelenetskaya Bay, probably due to interspecific competition with barnacles occupying the dorsal parts of the host. Juvenile barnacles and mussels dominated the fouling communities on the crabs. The age of barnacles did not exceed 2–4 months. However, the presence of 4-year-old mussels suggests that these older mollusks have been directly transferred from mussel beds to the hosts. Our results indicate that colonization by epibionts and symbionts is generally not disadvantageous for the crab hosts, except for some possible negative impacts of amphipods occupying the gills.     

On the growth of the blue king crab (<Emphasis Type="Italic">Paralithodes platypus</Emphasis>) population in the Peter the Great Bay of the sea of Japan

The causes of the appearance of large blue king crabs (Paralithodes platypus) in Peter the Great Bay for the last decade are discussed. This species is an important commercial resource in the waters of Russian Far Eastern seas, and its general concentrations are related mainly to the sublittoral and upper bathyal zones of the northwestern Bering Sea and the northern Sea of Okhotsk. Until recently, this species has been observed in areas along the continental coast of the northwestern Sea of Japan up to the Peter the Great Bay, where it incidentally showed up in red king crab (P. camtschaticus) and snow crab (Chionoecetes opilio) catches but was also commercially used. This area was considered as the southern periphery of the species range. Since the late 1990s, both male and female blue king crabs have been recorded in trawl and trap catches during research works conducted within the Peter the Great Bay. Since 2002, any commercial catches of shelf crab species are prohibited in the waters south of 47°20′ N because of a dramatic decline in their populations. Since then all the illegally caught crabs, including blue king crabs that are seized live from poachers, are released back into the water in certain places of the bay. In total, at least 29 503 blue king crabs, including egg-bearing females, were released within the period from 2002 to November 2009. At present, the overall blue king crab abundance in Peter the Great Bay, estimated based on the trap catches over an area of 7048 km², is 50500, the abundance of commercial-size males (with a carapace width over 130 mm) is 7500, and the male to female ratio is 1.00: 1.35. The increase in the blue king crab population observed in the bay is the result of the immigration of mature and viable individuals from other areas of its range. After this “uncontrolled introduction” blue king crabs adapted to new conditions, and then began breeding and spreading over the entire area of the bay.     

Some aspects of the biology of the amphipods <Emphasis Type="Italic">Ischyrocerus anguipes</Emphasis> associated with the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus,</Emphasis> in the Barents Sea

This paper describes size composition, morphometric, and reproductive parameters of the summer generation of the amphipod Ischyrocerus anguipes (Krǿyer, 1838) associated with the red king crab Paralithodes camtschaticus (Tilesius, 1815) in Dalnezelenetskaya Bay (southern Barents Sea, Russia). In summer 2004–2007, prevalence and mean number of I. anguipes per host were 15.0% and 6.9 ± 1.1 specimens, respectively. The majority of amphipods were found on the host carapace (47.4%) and the limbs (43.9%). High infestation indices and absence of negative impacts for the host indicate that I. anguipes is a facultative commensal of the red king crab. The amphipods sex ratio was significantly biased toward females (F:M = 2:1). Females had a greater size than males. The size at 50% maturity of I. anguipes females was estimated to be 3.37 mm. The number of eggs laid is linearly correlated with the size of a female. Some differences in biological features of symbiotic and free-living amphipods (data obtained in 1940–1950) may be explained by climatic changes in the Barents Sea or advantages of living on the crab.     

Microsporidia of the genera <Emphasis Type="Italic">Thelohania</Emphasis> (Thelohaniidae) and <Emphasis Type="Italic">Ameson</Emphasis> (Pereziidae) in two species of lithodid crabs from the Sea of Okhotsk

Diseases caused by microsporidia were found in the red king crab Paralithodes camtschaticus and the blue king crab P. platypus that inhabit the Sea of Okhotsk. Based on the histological features of the invasion and data on the morphological structure of the parasites, the microsporidia were assigned to the genera Thelohania and Ameson. Infected crabs exhibited severe destructive changes of their internal organs along with sharply pronounced external signs of disease. During the observation period, the microsporidian invasion was only found in females and young (unmarketable size) males from August to mid-October. Later, until mid-December, no diseased crabs were found.     

Epifauna associated with the northern stone crab <Emphasis Type="Italic">Lithodes maia</Emphasis> in the Barents Sea

Species composition, prevalence, and intensities of species colonizing the northern stone crab Lithodes maia in Dalnezelenetskaya Bay (Barents Sea) were examined. Sixteen species attached to the body surface or the host gills were identified. The most common associates were hydrozoans (100.0%), especially Obelia longissima, and the amphipods Ischyrocerus commensalis (93.8%). Species composition of the stone crab epifauna was similar to that observed for the Lithodid crab Paralithodes camtschaticus, except that tubular polychaetes Pomatoceros triqueter and Placostegus tridentatus were found only on the surface of the stone crab, while fish leeches Johanssonia arctica occurred on the red king crabs. Differences in percentage of infested hosts, and mean intensities of some associates are influenced by the conditions of carapace structure and size of both crab species.     

Walking speed and area utilization of red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) introduced to the Barents Sea coastal ecosystem

The red king crab (Paralithodes camtschaticus) was introduced in the Barents Sea in the 1960s and soon established a viable population. Proper management and exploitation of the Barents Sea king crab stock require better understanding of the spatial dynamics at different scales. This study examines the small-scale movement patterns of seven adult male crabs tracked for a period of up to one month from mid July to mid August at 150 m depth in a semi-enclosed fjord on the Russo-Norwegian border. The crabs were tagged with acoustic transmitters and their movements monitored with an acoustic positioning system. Low walking speeds (<0.01 m s⁻¹) were most frequent but the crabs could move at a maximum speed of 0.15 m s⁻¹ and walk an actual distance of up to 270 m over a period of one hour. However, the crabs usually moved within a relatively restricted area with mean hourly longest rectilinear distance varying from 26 to 64 m. The crabs alternated between periods of low and high activity, which could reflect feeding in and movements between food patches. The lack of a diel activity rhythm may be due to high light levels during the polar summer night, or a chemically mediated food search strategy.     

Red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) fisheries in Russian waters: historical review and present status

The red king crab (Paralithodes camtschaticus) is a highly valued delicacy on the international market and currently contributes significantly to the income from fisheries in the regions where it is harvested. Russian income from red king crab export is $200–250 million per year. We review both the biology and fishery of the two largest populations of this species in Russia, i.e., in western Kamchatka (Sea of Okhotsk) and in the Barents Sea. The latter was established in the mid-1990s after introduction of red king crab to the area in the 1960s. The Barents Sea crabs are larger, grow faster and mature earlier than the crabs from the Sea of Okhotsk owing to more favorable temperature conditions in the Barents Sea. Additionally, we provide fishery information for the Prymorie population of red king crab (Sea of Japan) that remains depressed and closed for commercial fishery at present. Although the fishery period of red king crab in western Kamchatka is much longer than in the Barents Sea (1930–present time vs. 2004–present time), similar patterns were observed for the exploited king crab populations. High annual landings led to a pronounced decrease in population density and total abundance that, in turn, led to closures or some limitations of fisheries. Subsequent rehabilitations of the populations provided an opportunity for reopening of the fisheries and further exploration of red king crab populations under sustainable management. The main reason explaining a decline in red king crab populations both in the North Pacific and in the Barents Sea is high, mainly illegal, fishing pressure. Sustainable harvest strategies for the fisheries could prevent negative scenarios (overfishing) in the future.     

Consumers of sea urchins,<Emphasis Type="Italic"> Paracentrotus lividus</Emphasis> and<Emphasis Type="Italic"> Arbacia lixula</Emphasis>, in shallow Mediterranean rocky reefs

Underwater observations on fish and asteroid consumers (i.e. predators and scavengers) of sea urchins, Paracentrotus lividus and Arbacia lixula, were carried out at several locations in shallow Mediterranean rocky reefs. Observations conducted in the marine reserve of Torre Guaceto (Adriatic Sea) revealed that sparid fishes, Diplodus sargus and D. vulgaris, are the main fish predators of small (<1 cm in test diameter) and medium (1–4 cm) sea urchins, whereas the labrids Coris julis and Thalassoma pavo preyed only upon small sea urchins. Large D. sargus were able to prey upon small and medium, and occasionally large (>4 cm) sea urchins, whereas medium and small Diplodus preyed mainly upon small sea urchins. The number of sea urchins preyed upon by fishes was negatively related to sea urchin size for both species. P. lividus appeared to be subject to higher predation levels than A. lixula. The scavenger guild comprised 11 fish species, with D. sargus, D. vulgaris, Coris julis and Chromis chromis accounting for about 80% of scavenger fishes. Observations performed at several locations in the Mediterranean on the predatory asteroid Marthasterias glacialis revealed that only 3% of the detected individuals were preying upon sea urchins. Due to the importance of sea urchins for assemblage structure and functioning of Mediterranean rocky reef ecosystems, these results may have also important implications for management of fishing activities.Communicated by H.-D. Franke     

Epibionts of the red king crab Paralithodes camtschaticus (Tilesius, 1815) in Sayda Inlet of Kola Bay

The species composition of organisms associated with the red king crab Paralithodes camtschaticus (Tilesius, 1815) was investigated in Sayda Inlet of Kola Bay in 2004–2005. Nine fouler species and three symbiotic species were found on the carapaces of the red king crab. Balanus crenatus Bruigere 1789 barnacles were the most abundant fouler species and were found on 14.8% of the crabs. Symbiotic amphipods Ischyrocerus commensalis Chevreux, 1900 were found for one-tenth of all the crabs studied. The mean intensity of the amphipods was significantly greater for September, when the reproduction period of this species occurred. Male and female crabs were hosted with the same intensity. The number of host crabs increased accordingly to the crab size. The proportion of hosted crabs was three-fold less in Sayda Inlet than in the less polluted areas of the Barents Sea.     

Peculiarities of reproductive biology and larval development of the red king crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> 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.     

Distribution and some features of biology of sea raven <Emphasis Type="Italic">Hemitripterus villosus</Emphasis> (Hemitripteridae) in the northwestern part of the Sea of Japan

On the basis of long-term (1981–2008) observations, it was shown that, in the northwestern part of the Sea of Japan, sea raven Hemitripterus villosus is a common species with low, but stable numbers and it is a part of elittoral ichthyocenoses. During the year it performs wintering, feeding, and spawning migrations within the shelf and the upper part of the continental slope occurring from almost the water’s edge to a depth of 550 m. Highest density of sea raven is observed in Peter the Great Bay and the lowest is observed off the coasts of northern Primorye. Maximum length of H. villosus in the northwestern part of the Sea of Japan reaches 57 cm, and the modal group of fish consists of fish with a length of 25–45 cm (75%). In Peter the Great Bay, in the summer period, individuals with a length of 11–50 cm feed mainly on mass fish species; the value of daily ration of H. villosus varies from 1.6 to 3.2% of body weight, averaging 2.5%. According to an expert estimate, the biomass of sea raven in the northwestern part of the Sea of Japan reaches 2000 t.     

Distribution of neurons containing catecholamines in brain of hermit crab <Emphasis Type="Italic">Pagurus middendorffii</Emphasis> and of king crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Anomura,Decapoda)

Distribution of catecholamine-containing neurons in the brain of two species of crustaceans—hermit crab Pagurus middendorffii and the king crab Paralithodes camtschaticus was studied by immunocytochemical methods using an antibody against tyrosine hydroxylase (TH). In both species of the studied crustaceans, morphologically different types of TH-immunoreactive neurons are detected in cell clusters in brain protocerebrum, deutocerebrum, and tritocerebrum. Similarities and differences in the topography, numbers, and morphology of TH-positive neurons in different brain structures in the hermit crab and king crab are discussed.     

Can multitrophic interactions and ocean warming influence large‐scale kelp recovery?

Ongoing changes along the northeastern Atlantic coastline provide an opportunity to explore the influence of climate change and multitrophic interactions on the recovery of kelp. Here, vast areas of sea urchin‐dominated barren grounds have shifted back to kelp forests, in parallel with changes in sea temperature and predator abundances. We have compiled data from studies covering more than 1,500‐km coastline in northern Norway. The dataset has been used to identify regional patterns in kelp recovery and sea urchin recruitment, and to relate these to abiotic and biotic factors, including structurally complex substrates functioning as refuge for sea urchins. The study area covers a latitudinal gradient of temperature and different levels of predator pressure from the edible crab (Cancer pagurus) and the red king crab (Paralithodes camtschaticus). The population development of these two sea urchin predators and a possible predator on crabs, the coastal cod (Gadus morhua), were analyzed. In the southernmost and warmest region, kelp forests recovery and sea urchin recruitment are mainly low, although sea urchins might also be locally abundant. Further north, sea urchin barrens still dominate, and juvenile sea urchin densities are high. In the northernmost and cold region, kelp forests are recovering, despite high recruitment and densities of sea urchins. Here, sea urchins were found only in refuge habitats, whereas kelp recovery occurred mainly on open bedrock. The ocean warming, the increase in the abundance of edible crab in the south, and the increase in invasive red king crab in the north may explain the observed changes in kelp recovery and sea urchin distribution. The expansion of both crab species coincided with a population decline in the top‐predator coastal cod. The role of key species (sea urchins, kelp, cod, and crabs) and processes involved in structuring the community are hypothesized in a conceptual model, and the knowledge behind the suggested links and interactions is explored.     

Histopathological Changes Associated with Shell Disease in the Red King Crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius, 1815)

Histopathological changes have been revealed associated with shell disease in the red king crab, Paralithodes camtschaticus. The changes in the gills, esophagus, stomach, hepatopancreas, heart, and antennal glands of the crabs are described.     

Hepatopancreas cell cultures from mud crab, <Emphasis Type="Italic">Scylla paramamosain</Emphasis>

Hepatopancreas is an important digestive and endocrine organ in crustacean. However, there are few reports on cell cultures from crabs. Here, the cell cultures of hepatopancreas from Scylla paramamosain was studied in vitro. Both the primary cell culture and subculture were grown in Leibovitz’ L-15 medium, M199 medium, or a specially designed medium for S. paramamosain (MSP). The results showed that hepatopancreas cells in vitro grew in compact clusters in 2–3 d. Four types of cells could be identified. They were embryo cells, fibrillar cells, resorptive cells, and blister-like cells, respectively. Some of these cells could be subcultured for three generations. The MSP supported the best survival of these hepatopancreas cells, while M199 medium was the least effective of these three media. Fetal bovine serum and crab muscle extracts as supplements stimulated growth, but the crab hemolymph inhibited cell growth. Taken together, MSP is an appropriate medium for hepatopancreas cell cultures from S. paramamosain and can support cultures through several passages.     

On the biology of the Japanese swimming crab <Emphasis Type="Italic">Charybdis japonica</Emphasis> (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.     

Temporal and spatial patterns of organic carbon are linked to egg deposition by beach spawning horseshoe crabs (<Emphasis Type="Italic">Limulus polyphemus</Emphasis>)

The spring spawning by the American horseshoe crab (Limulus polyphemus L.) results in temporally and spatially discrete inputs of eggs onto sandy beaches in Delaware Bay, USA. We tested the hypothesis that seasonal patterns of sediment organic carbon on Delaware Bay beaches is linked to this pulsed input of horseshoe crab eggs. At a location with minimal horseshoe crab spawning activity (Higbee Beach), there was little seasonal variation in sediment organic carbon, no distinction between organic carbon levels as a function of shoreline position or sediment depth, and no significant correlation between the abundance of crab eggs and percent organic carbon. Conversely, at a prime horseshoe crab spawning habitat (North Beach), organic carbon levels were seasonally pulsed and were correlated with egg abundance. Moreover, the strongest evidence of seasonality was seen at the middle foreshore location at the 15–20 cm depth, consistent with the highest input of horseshoe crab eggs. Although some of the organic carbon contributed by horseshoe crab eggs in May–June leaves the beach in the form of hatched larvae later in the year, there is a net input of organic carbon to the system in the form of unfertilized and/or dead eggs, egg membranes, and embryonic molts. We suggest that the inputs of eggs from horseshoe crabs and other beach spawning animals, such as grunion and capelin, make significant contributions to the energy budget of sandy beaches.     

<Emphasis Type="Italic">Haliphthoros milfordensis</Emphasis> isolated from black tiger prawn larvae (<Emphasis Type="Italic">Penaeus monodon</Emphasis>) in Vietnam

 A marine fungus was isolated from the black tiger prawn Penaeus monodon at Nha Trang, Vietnam, on March 20, 2001 and named isolate NJM 0131. The fungus was identified as Haliphthoros milfordensis from the characteristics of asexual reproduction, and its physiological characteristics were investigated. Although the optimum temperature for growth of the isolate was 25°–30°C, the fungus grew at a wide range of temperatures (15°–40°C). H. milfordensis grew well in 50%–100% seawater, but poorly in PYG agar containing 1.0%–5.0% NaCl and KCl. The fungus grew at a wide range of pH (4.0–11.0) with the optimum pH value of 7.0–9.0. The isolate also showed pathogenicity to swimming crab larvae (Portunus trituberculatus) by artificial infection, but mortality was not high. This is the first report of disease in the black tiger prawn P. monodon in Vietnam caused by H. milfordensis. Received: July 22, 2002 / Accepted: January 21, 2003 Correspondence to:K. Hatai     

The first report of <Emphasis Type="Italic">Spondias</Emphasis> native to Madagascar: <Emphasis Type="Italic">Spondias tefyi</Emphasis>, sp. nov. (Anacardiaceae)

Spondias represents a genus new to Madagascar’s native flora. Like Campnosperma, it is now known from both American and Asian tropics and Madagascar but not from continental Africa. The new species Spondias tefyi is easily distinguished from all of its Asian congeners by having the stamens shorter than the pistil and fruits brown and lenticellate at maturity (vs. greenish, yellow, orange or red, and relatively smooth). The new species is one of several Anacardiaceae whose fruits are eaten by lemurs in the Analavelona Forest, highlighting the importance of conserving this threatened subhumid forest remnant in southern Madagascar.