Enigmatic hotspot of crayfish diversity at risk: Invasive potential of non‐indigenous crayfish if introduced to New Guinea

1. The large island of New Guinea has a rich indigenous astacofauna represented by numerous parastacids from the genus Cherax. The western half of the island is part of Indonesian territory.
2. Indonesia is known to be the main exporter of ornamental crayfish globally, and certain New Guinean species are exploited as ornamentals within the international pet trade. Moreover, one non‐indigenous species has been previously recorded being cultured in Java, Indonesia. This species, the North American Procambarus clarkii, is a vector of crayfish plague, the disease that is lethal to most parastacids. This population has already tested positive for the disease.
3. As the transport of non‐indigenous crayfish within the Indonesian territory is not restricted, their introduction to New Guinea can be expected. The Indonesian market was therefore surveyed for ornamental crayfish and their environmental suitability evaluated, as represented by temperature during the drought and rainy seasons in New Guinea.
4. Four North American and one Australian species were found advertised for sale. One of them, P. clarkii, was assessed as the most damaging species, followed by other North American species. A total ban on the culture and transport of the highest risk crayfish species in Indonesia and Papua New Guinea is recommended.

     

Procambarus clarkii Girard as a vector for the crayfish plague fungus, Aphanomyces astaci Schikora

Abstract. Procambarus clarkii Girard, a native freshwater crayfish species of Lousiana, USA, was found to harbour the crayfish plague fungus, Aphanomyces astaci Schikora, in its cuticle as a benign infection. Under certain conditions, P. clarkii dies as a result of this parasite, and the A. astaci infection then becomes acute and can be transmitted to Astacus astacus (L.).
Therefore, it is now shown that at least three different species of North American crayfish ( Pacifastacus leniusculus Dana, Orconectes limosus Raff, and Procambarus clarkii Girard) can carry the crayfish plague fungus, A. astaci , can transfer the disease to other crayfish species, and under certain circumstances can die of its own infection.     

Predation by native sunfishes (Centrarchidae) on the invasive crayfish Orconectes rusticus in four northern Wisconsin lakes

Tetzlaff JC, Roth BM, Weidel BC, Kitchell JF. Predation by native sunfishes (Centrarchidae) on the invasive crayfish Orconectes rusticus in four northern Wisconsin lakes.
Ecology of Freshwater Fish 2011: 20: 133–143. © 2010 John Wiley & Sons A/S Abstract – Introduced rusty crayfish (Orconectes rusticus) often establish abundant populations in lakes where they negatively impact native food webs. However, rusty crayfish do not become abundant in all lakes. Fish predation has been posed as one potential mechanism limiting rusty crayfish density, but there is limited empirical evidence to support this hypothesis. Using a case study approach, we quantified the extent and timing of predation on nonnative rusty crayfish by three native centrarchids in four northern Wisconsin lakes with contrasting crayfish densities. We estimated population‐level predation effects on rusty crayfish using bioenergetics models in combination with fish and crayfish abundance estimates. Bluegill (Lepomis machrochirus) and pumpkinseed (Lepomis gibbosus) consumed young‐of‐year crayfish exclusively whereas rock bass (Ambloplites ruspestris) consumed a wide size range of crayfish. Rusty crayfish were found in Lepomis diets primarily in late June and early July while rock bass consumed crayfish throughout the summer. Per individual, rock bass consumed more crayfish biomass than Lepomis, but at the population‐level, higher Lepomis densities resulted in greater numbers of crayfish and more crayfish biomass consumed by Lepomis than rock bass. Lepomis populations consumed 8 × , 14 × , 22 × and 120 × more individual crayfish than rock bass populations in the four study lakes. Bioenergetics simulations revealed that dense populations of Lepomis were capable of consuming a large percentage of the juvenile crayfish population in two of our study lakes. In systems with high Lepomis densities, Lepomis consumption of juvenile rusty crayfish may play a significant role in the invasion and establishment dynamics of rusty crayfish.     

Red swamp crayfish,Procambarus clarkii,found in South Africa 22 years after attempted eradication

1. No freshwater crayfish are indigenous to continental Africa, but four species have been introduced to the continent. One of these is the North American red swamp crayfish Procambarus clarkii, which has been introduced into several African countries, mainly for aquaculture, and has had demonstrable impacts where it has escaped captivity. In South Africa, the documentation of this species in farm dams near Dullstroom and the adjacent Crocodile River in 1988 resulted in an eradication attempt in 1994, with unknown results. 2. In order to evaluate the status of P. clarkii in South Africa, dams on the previously invaded farm and the Crocodile River were sampled four times between December 2015 and June 2016 using visual surveys, trapping, dipnetting and electrofishing. This yielded a single reproductively active male P. clarkii from one of the farm ponds, while many other native aquatic species were found in high numbers. 3. It is clear from this study that P. clarkii was not eradicated in South Africa and that individuals have been surviving in the wild (i.e. outside captivity or cultivation) for at least 28 years in the location where it was introduced. Containment and eradication of the species are proposed as management actions, which have major importance in preventing undesirable further spread or translocation of this species into new aquatic environments in South Africa.     

Growth and Survival of Juvenile Orconectes virilis and Orconectes immunis at Different Temperatures1

Culture of orconectid crayfishes in the midwestern USA offers the potential of contributing to a year-round supply of fresh product as summer/fall production would augment winterhpring production in the southern USA. However, relatively little basic biological information exists for this potential new aquaculture crop. In this study, the authors reared juvenile (third instar) Orconectes virilis and Orconectes immunis at either 10, 15, 20, 25 or 30 C and measured weight gain and survival over a 21 day period. Orconcctes immunis juveniles were larger than O. virilis at the third instar and gained weight more rapidly in this experimental system. Gains in weight and length for both species increased as temperature increased from 10 to 25 C. Both values were lower in crayfish reared at 30 C, though number of molts was the same in crayfish reared at 25 or 30 C. Thus, there appears to be a bioenergetic cost of rearing orconectid crayfishes in temperatures above 25 C. Further, incremental growth with successive molts was influenced by water temperature.     

Colonization history and human translocations explain the population genetic structure of the noble crayfish (Astacus astacus) in Fennoscandia: Implications for the management of a critically endangered species

1. The noble crayfish (Astacus astacus) is an endangered freshwater species in Europe. The main threat is from lethal crayfish plague, caused by the oomycete Aphanomyces astaci that has been spread over Europe by introduced North American crayfish species, acting as chronic carriers of the disease.
2. Most of the remaining noble crayfish populations are found in the Baltic Sea area, and there is an urgent need to implement conservation actions to slow down or halt the extinction rate in this region. However, limited knowledge about the genetic structure of populations in this area has so far precluded the development of conservation strategies that take genetic aspects into consideration.
3. Key objectives of this large-scale genetic study, covering 77 locations mainly from northern Europe, were to describe the contemporary population genetic structure of the noble crayfish in the Fennoscandian peninsula (Sweden, Norway, and Finland), taking postglacial colonization history into account, and to evaluate how human activities such as stocking have affected the genetic structure of the populations.
4. Analyses of 15 microsatellite markers revealed three main genetic clusters corresponding to populations in northern, middle, and southern Fennoscandia, with measures of genetic diversity being markedly higher within populations in the southern cluster. The observed genetic structure probably mirrors two main colonizations of the Baltic Sea basin after the last glaciation period. At the same time, several deviations from this pattern were observed, reflecting past human translocations of noble crayfish.
5. The results are discussed in relation to the conservation and management of this critically endangered species. In particular, we recommend increased efforts to protect the few remaining noble crayfish populations in southern Fennoscandia and the use of genetic information when planning stocking activities, such as reintroductions following local extinctions.

     

Time‐series analysis of native and non‐native crayfish dynamics in the Thames River Basin (south‐eastern England)

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The North American signal crayfish,Pacifastacus leniusculus (Dana), established in the wild in Scotland

1. Although the North American signal crayfish, Pacifastacus leniusculus (Dana), has been brought into Scotland for aquaculture several times in the past, there appears to be no record of it ever having become established in the wild here. 2. The species is now recorded as being well established at a stream site in south-west Scotland where many specimens were collected in the summer of 1995. Local information indicates that the species has occurred there for several years. 3. The significance of this record is that Scotland is no longer free from this aggressive and invasive species. Fortunately, this locality is far away from the only population of the native white-clawed crayfish Austropotamobius pallipes (Lereboullet), an introduced stock which has been long established in north-west Scotland.     

Hosts and transmission of the crayfish plague pathogen Aphanomyces astaci: a review

The crayfish plague pathogen, Aphanomyces astaci Schikora, has become one of the most well‐studied pathogens of invertebrates. Since its introduction to Europe in the mid‐19th century, it has caused mass crayfish mortalities, resulting in drastic declines of local populations. In contrast, North American crayfish usually serve as latent carriers, although they may also be negatively affected by A. astaci infections under some circumstances. Recent research benefiting from molecular tools has improved our knowledge about various aspects of A. astaci biology. In this review, we summarize these advances, particularly with respect to the host range and transmission. We highlight several aspects that have recently received particular attention, in particular newly confirmed or suspected A. astaci hosts, latent A. astaci infections in populations of European crayfish, and the relationship between A. astaci genotype groups and host taxa.     

克氏原螯虾染色体及其核型

染色体是遗传物质的载体,是研究细胞遗传学的基础,为研究克氏原螯虾染色体及其核型,实验以性未成熟雄性个体的精巢为材料,采用低渗和空气干燥常规方法制备细胞分裂中期染色体标本,研究了克氏原螯虾染色体及核型。Giemsa和DAPI染色后在显微镜下观察到清晰的精母细胞减数分裂中期二价体和精原细胞有丝分裂中期染色体时相。对减数分裂中期二价体及有丝分裂中期染色体进行了数目上的统计。结果显示,克氏原螯虾二倍与单倍染色体数目分别为2N=188和N=94。由于有丝分裂染色体形状微小,核型分析困难,故选取减数分裂中期二价体,根据长度及着丝点位置对其进行了初步核型分析,核型公式为N=55M+22(SM,ST)+17T,未发现异形性染色体。     

Thermal habitat quality of aquatic organisms near power plant discharges: potential exacerbating effects of climate warming

Water temperature strongly affects aquatic ectotherms, as even slight temperature changes can have dramatic effects on physiological rates. Water bodies receiving industrial thermal discharges can undergo dramatic spatial and temporal changes in water temperature. To quantify effects on aquatic ectotherms, thermal habitat quality (bioenergetic growth rate potential; GRP) for zebra mussel, Dreissena polymorpha (Pallas), rusty crayfish, Orconectes rusticus (Girard), walleye, Sander vitreus (Mitchill) and smallmouth bass, Micropterus dolomieu (Lacepède) was estimated near two power plant thermal discharges on the Ohio River, USA, from 2010 to 2012 using bioenergetics models. These results were then compared with GRP under increased base temperatures representing climate warming. Growth rate potential for all species was low near the discharges during summer and highest in winter, with increasing prey consumption minimising the negative effects of increased temperatures. In their immediate vicinity, thermal discharges had a more adverse effect on GRP than plausible climate warming but primarily affected GRP over a small spatial area, particularly within 400 m downstream from the power plants. Examining thermal habitat suitability will become increasingly important as rising energy demand and climate change collectively affect aquatic organisms and their habitats.     

The relationship between water quality and indigenous and alien crayfish distribution in the Czech Republic: patterns and conservation implications

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Resolving species identification problems in the genus Sebastes using nuclear genetic markers

The identification of North Atlantic redfish has been controversial and remains a difficult task due to overlapping of meristic and morphological characters. Here we used nine microsatellite loci to assess the level of genetic differentiation among these species and assess the resolution power of these microsatellite loci for individual assignment-based analyses. Conventional analyses as well as individual Bayesian assignment methods clearly separated the four species of North Atlantic redfish as well as the giant form of Sebastes marinus and the so-called “oceanic” and “deep-sea” types of Sebastes mentella. Locus-by-locus analyses revealed that only five microsatellite loci out of nine used could discriminate the concerned species. The advantage of the Bayesian methods relies in the individual information retrieved. It therefore gave additional information on the interrelationship among species. Indeed, we provide evidence of potential hybridization among species as well as individual misclassification based on morphological identification. We provide a powerful tool to discriminate North Atlantic redfish species, which might be useful for legal issues such as poaching, unintentional harvesting and control label.     

Comparison of the survival, growth and yield of red swamp crayfish and white river crayfish in monoculture and polyculture systems

Red swamp crayfish (Procambarus clarkii) and white river crayfish (P. acutus acutus) production for monoculture and polyculture systems were compared. The experiment consisted of three treatments with six replicates each. The stocking rates were 43 crayfish/m² in 0.18-m² tanks fitted with a stand of green rice. Each tank contained six crayfish, either six individuals of the same species or three individuals of each species. The mean stocking size for monoculture and polyculture were 32.6 ± 0.05 and 33.0 ± 0.07 mm total length, respectively. Survival and growth was assessed at 30-day intervals over a 90-day experimental period. Survival of two species was the same in the monoculture system (62.5%). Survival of P. clarkii in the polyculture system (25.0%) was significantly lower than in the monoculture system (62.5%), whereas P. acutus acutus survived at similar rate in the polyculture system (41.7%) and monoculture system (62.5%). Survival was lower but growth was higher in the polyculture system than in the monoculture system for both species. Growth of P. acutus acutus in the polyculture system was significantly greater than in the monoculture system. No difference was observed in the growth of P. clarkii between polyculture and monoculture and the overall growth of P. acutus acutus and P. clarkii was similar for the 90 days. Yield did not differ significantly between monoculture and polyculture systems (P < 0.05). Total yields were in 1.15 kg/ha in monoculture and 1.18 kg/ha in polyculture.     

Growth performance and muscle composition response to reduced feeding levels in juvenile red swamp crayfish Procambarus clarkii (Girard, 1852)

Overfeeding in aquaculture can lead to suboptimal growth and increased production costs. Red swamp crayfish, Procambarus clarkii, is one of the most noteworthy species cultured in China, but little information is available on the optimal feeding levels of this species, especially in ponds cultured with macrophytes. In this study, we tested the effects of five different feeding levels (20%, 40%, 60%, 80% and 100% satiation) of an artificial diet on growth performance and muscle composition of juvenile P. clarkii in 15 concrete ponds cultured with the macrophyte Hydrilla verticillata (three replicates for each treatment). The results showed that growth performance decreased only when feeding levels were below 60% satiation. Muscle composition analysis revealed that the moisture and ash contents of muscle did not vary significantly with feeding levels but that the lipid and protein contents of muscle significantly decreased when P. clarkii was fed to 40% satiation. Stable isotope analysis suggested a shift in crayfish diets to easily available H. verticillata when feeding levels decreased. With this study, we hope to encourage crayfish farmers to reduce feeding levels and increase natural food items such as macrophytes in cultured ponds to maximize crayfish yields and reduce production costs.     

Relative impacts of native and non‐native crayfish on shelter use by an indigenous benthic fish

• 1. The North American signal crayfish Pacifastacus leniusculus has been widely introduced throughout Europe where it is expanding its range and in many areas replacing the native white‐clawed crayfish Austropotamobius pallipes. There is concern with regards to the impact of this species replacement on benthic fish. Interspecific behavioural interactions and competition for shelter between the benthic fish, bullhead Cottus gobio and A. pallipes and P. leniusculus were measured to assess the comparative impact of native and non‐native crayfish.
• 2. Both white‐clawed crayfish and signal crayfish were dominant over bullhead. Bullheads moved away from approaches of crayfish, left shelters on entry of crayfish and rarely entered an occupied shelter. Signal crayfish made significantly more aggressive approaches towards bullheads than white‐clawed crayfish.
• 3. Alone, bullheads spent most of their time by day under shelter (median 96%), reflecting a highly entrained behavioural response, which was relaxed by night (median 60%). Both crayfish species reduced shelter use by bullheads although the extent of shelter sharing by bullheads was higher in trials with white‐clawed crayfish than with signal crayfish.
• 4. Sampling in the River Wharfe, northern England, where signal and white‐clawed crayfish and bullhead currently exist, demonstrated a negative relationship between the densities of signal crayfish and bullhead, with high bullhead abundance where crayfish were absent or where white‐clawed crayfish were present at low density.
• 5. Assuming that shelter is sometimes limited under natural conditions, crayfish are likely to displace bullheads from shelters, which may increase predation risk for bullheads. Although the effects of signal crayfish on bullhead shelter use were more intense, the pattern was highly evident for the native white‐clawed crayfish. The higher fecundity and densities attained by signal crayfish may be more significant than differences in the behaviour of the two crayfish species in determining the impact of crayfish on bullheads.

Copyright © 2008 John Wiley & Sons, Ltd.     

Modelling effects of disturbance on population dynamics of generalized crayfish life history strategies

1. Crayfish play a crucial ecological role and are often considered a keystone species within freshwater ecosystems; however, North American crayfish species face disturbance and ecological threats including invasive species and intensified drought.
2. Demographic models can allow examination of population dynamics of a targeted species under a wide variety of disturbance scenarios. In this study, crayfish population dynamics were modelled and their responses to simulated biological invasions and drought were assessed.
3. As life history data on crayfish are relatively rare, models were used to explore the population viability of four generalized species with distinct life history strategies under 11 disturbance scenarios. RAMAS-Metapop was used to construct stage-based demographic metapopulation models parameterized using vital rates from established literature sources.
4. Models indicated that populations respond differentially to disturbance based on life history. However, both r- and K-selected species appear to be highly susceptible to decline when faced with the additive effects of reduced carrying capacity resulting from invasion and reduced survival rates caused by drought.
5. Constructing models that explore a broad array of life histories and disturbance regimes can provide managers with tools to develop generalized, widely applicable conservation strategies in data-depauperate systems.

     

Aphanomyces astaci presence in Japan: a threat to the endemic and endangered crayfish species Cambaroides japonicus?

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Growth responses of juvenile red swamp crayfish, Procambarus clarkii Girard, to several diets under controlled conditions

The growth responses of juvenile crayfish, Procambarus clarkii Girard, to diets based on common fresh feedstuffs available from agriculture and freshwater ecosystems were studied under controlled laboratory conditions. The dietary treatments were: fresh leaves and shoots of watercress, fresh potato tubers, fresh fish meat from mosquitofish, and all the possible combinations of those ingredients on alternate feeding days. After 22 days, the results showed a significantly higher growth rate (P= 0.05) in crayfish fed with mosquitofish meat. The differences were not significant between the other treatments, but those which included fish meat induced growth rates consistently higher than those based only on plant ingredients. This trend was maintained until the end of the experiment. These results suggest that a dietary supplement based on animal ingredients might significantly improve growth rate and yield, provided the economic feasibility of such a production process be confirmed in field trials. However, it was not clear whether this was because of protein, or lipid concentration and composition of mosquitofish meat. Further research must also clarify the role of vegetable ingredients in dietary composition, as well as the effect of microbial populations occurring during the decomposition of plant material on its nutritional properties for crayfish.     

Crayfish in central and southern Ukraine with special focus on populations of indigenous crayfish Astacus pachypus (Rathke, 1837) and their conservation needs

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