Invasive Crayfish Procambarus Clarkii Research Articles

Geostatistical distribution modelling of two invasive crayfish across dendritic stream networks

Species distribution models combining environmental and spatial components are increasingly used to understand and forecast species invasions. However, modelling distributions of invasive species inhabiting stream networks requires due consideration of their dendritic spatial structure, which may strongly constrain dispersal and colonization pathways. Here we evaluate the application of novel geostatistical tools to species distribution modelling in dendritic networks, using as case study two invasive crayfish (Procambarus clarkii and Pacifastacus leniusculus) in a Mediterranean watershed. Specifically, we used logistic mixed models to relate the probability of occurrence of each crayfish to environmental variables, while specifying three spatial autocorrelation components in random errors. These components described spatial dependencies between sites as a function of (1) straight-line distances (Euclidean model) between sites, (2) hydrologic (along the waterlines) distances between flow-connected sites (tail-up model), and (3) hydrologic distances irrespective of flow connection (tail-down model). We found a positive effect of stream order on P. clarkii, indicating an association with the lower and mid reaches of larger streams, while P. leniusculus was affected by an interaction between stream order and elevation, indicating an association with larger streams at higher altitude. For both species, models including environmental and spatial components far outperformed the pure environmental models, with the tail-up and the Euclidean components being the most important for P. clarkii and P. leniusculus, respectively. Overall, our study highlighted the value of geostatistical tools to model the distribution of riverine and aquatic invasive species, and stress the need to specify spatial dependencies representing the dendritic network structure of stream ecosystems.

Using eDNA to detect the distribution and density of invasive crayfish in the Honghe-Hani rice terrace World Heritage site.

The Honghe-Hani landscape in China is a UNESCO World Natural Heritage site due to the beauty of its thousands of rice terraces, but these structures are in danger from the invasive crayfish Procambarus clarkii. Crayfish dig nest holes, which collapse terrace walls and destroy rice production. Under the current control strategy, farmers self-report crayfish and are issued pesticide, but this strategy is not expected to eradicate the crayfish nor to prevent their spread since farmers are not able to detect small numbers of crayfish. Thus, we tested whether environmental DNA (eDNA) from paddy-water samples could provide a sensitive detection method. In an aquarium experiment, Real-time Quantitative polymerase chain reaction (qPCR) successfully detected crayfish, even at a simulated density of one crayfish per average-sized paddy (with one false negative). In a field test, we tested eDNA and bottle traps against direct counts of crayfish. eDNA successfully detected crayfish in all 25 paddies where crayfish were observed and in none of the 7 paddies where crayfish were absent. Bottle-trapping was successful in only 68% of the crayfish-present paddies. eDNA concentrations also correlated positively with crayfish counts. In sum, these results suggest that single samples of eDNA are able to detect small crayfish populations, but not perfectly. Thus, we conclude that a program of repeated eDNA sampling is now feasible and likely reliable for measuring crayfish geographic range and for detecting new invasion fronts in the Honghe Hani landscape, which would inform regional control efforts and help to prevent the further spread of this invasive crayfish.

Impacts of Myriophyllum aquaticum invasion in a Mediterranean wetland on plant and macro-arthropod communities

The invasion by alien macrophytes in aquatic ecosystems may produce a strong alteration of the native aquatic vegetation leading to heavy impacts for both plant and faunal native diversity. Myriophyllum aquaticum is an aquatic plant native of Southern America, invasive in several part of the world. We studied the effects of M. aquaticum invasion on plant and macro-arthropod communities in the canals around a protected wetland in the Mediterranean basin. We sampled plant and macro-arthropod communities in 10 transects in invaded and non-invaded tracts of the canals. We assessed the differences in plant and macro-arthropod species richness, diversity, taxonomic diversity and species composition between invaded and non-invaded habitats by means of univariate and multivariate analyses. Our study shows a significant loss of plant diversity between non-invaded to invaded sites, leading to communities numerically and taxonomically impoverished and highly divergent in the species composition. We also detected significant differences in arthropod species composition between invaded and non-invaded transects. Some taxa such as mosquitoes and malacostraca were more frequent in the M. aquaticum-dominated stands. Furthermore, the study shows a positive relation between invaded habitats and juvenile individuals of the invasive alien crayfish Procambarus clarkii.

Modelling the predation effects of invasive crayfish, Procambarus clarkii (Girard, 1852), on invasive zebra mussel, Dreissena polymorpha (Pallas, 1771), under laboratory conditions

The functional response of a predator is a key factor regulating the population dynamics of predator-prey systems. This aspect of predatory behaviour must be assessed together with the effects of satiation by overabundant prey when evaluating the potential of biocontrol. The goals of this study were: (1) to identify the consumption rates of juvenile stages of the invasive zebra mussel, Dreissena polymorpha, by the invasive crayfish Procambarus clarkii; (2) to determine the predator functional response; (3) to evaluate the effects of predator satiation on the intensity of predation; and (4) to model the potential impacts of predation by this crayfish on zebra mussel populations. When presented with a range of mussel abundances, P. clarkii showed a functional response of type II, where the mortality of prey increases with decreasing prey abundance. P. clarkii also exhibited a satiation effect, diminishing its consumption rate from 33 mussels/day to 6 mussels/day over a 6-day period. By combining the effects of the functional response and of predator satiation we produced a model that predicts the complete consumption of local populations of up to 150/160 juveniles by one single crayfish over the period of 1 month. This impact may be important in low-density populations or in populations at equilibrium of D. polymorpha, and will be greater the higher the synchronization between the prey reproductive cycle and the activity period of the predator.

Temporary pond ecosystem functioning shifts mediated by the exotic red swamp crayfish (Procambarus clarkii): a mesocosm study

Temporary ponds, acknowledged for their conservation value, are colonized by the invasive crayfish Procambarus clarkii. We have tested the consequences of this colonization for the ecosystem under two contrasted scenarios: one single individual arrival or three individuals arrival. We recreated the temporary pond ecosystem in 1 m2 tanks to investigate the impact of the two crayfish densities. We studied the macrophyte community composition and abundance, chlorophyll a and total suspended solids concentrations, and the diversity and functional composition of micro-crustacean and macro-invertebrate communities. We observed a reduction of macrophyte biomass in experimental crayfish mesocosms in comparison with control tanks, nearly 80 and 40% less in 3 and 1 crayfish/m2 tanks, respectively. The macrophyte community shifted, followed by a filamentous algae development, an increase of bare sediment and turbidity in crayfish tanks. The macro-invertebrate community suffered a richness loss of 28 and 22%, in 3 and 1 crayfish/m2 tanks, respectively. Functionally, macro-invertebrate diversity reduction most strongly affected the grazer, detritivore and predator trophic groups. Microcrustaceans seemed not to be affected by the introduction of the crayfish. The introduction of the crayfish greatly altered the ecosystem structure and subsequently the ecosystem functioning.

Direct and indirect effects of an invasive omnivore crayfish on leaf litter decomposition

Invasive alien species (IAS) can disrupt important ecological functions in aquatic ecosystems; however, many of these effects are not quantified and remain speculative. In this study, we assessed the effects of the invasive crayfish Procambarus clarkii (Girard, 1852) on leaf litter decomposition (a key ecosystem process) and associated invertebrates using laboratory and field manipulative experiments. The crayfish had significant impacts on leaf decomposition due to direct consumption of leaf litter and production of fine particulate organic matter, and indirectly due to consumption of invertebrate shredders. The invertebrate community did not appear to recognize P. clarkii as a predator, at least in the first stages after its introduction in the system; but this situation might change with time. Overall, results suggested that the omnivore invader P. clarkii has the potential to affect detritus-based food webs through consumption of basal resources (leaf litter) and/or consumers. Recognizing that this IAS is widespread in Europe, Asia and Africa, and may attain high density and biomass in aquatic ecosystems, our results are important to develop strategies for improving stream ecosystem functioning and to support management actions aiming to control the invasive omnivore P. clarkii.

Biometric relationships of the invasive crayfish Procambarus clarkii to the Egyptian freshwater drainage canals

The specimens of the freshwater crayfish, Procambarus clarkii were collected from the River Nile tributaries at Al-Kanater Al- Khairiya, Qalyoubia governorate during the period from April 2010 to October 2011. The individuals of this species are small lobster-like freshwater crustacean. They have hard- rigid outer exoskeleton, and dark- red, or deep brownish color carapace, characterized by prominent whitish granules during the intermolt stages. The mature individuals of this species are varied from 6 to 10.5 cm in standard length, and from 6.5 to 11.5 cm in total length, and ranged between 10.38 and 56.34 gm in total body weight. The biometric study indicated that the relationship between body weight and standard length for the whole population (males and females) of this species is curvilinear, with positive regression coefficient b (slope) equals to 2.998, indicates to an isometric growth and correlation coefficient r 0.994, denotes to stability of this species at the prevailing environmental factors. For sex separate, the value of b showed also positive isometric regression coefficients, up to 3.359 and 3.118 for males and females respectively, indicating to slightly heavier males than females, without significance difference between sexes (T-test = 1.36, P > 0.05). These results also showed that, the values of regression coefficients b for the whole population during different seasons indicated heavier males and females during spring (3.719) and winter (3.879) than those in summer (3.091) and autumn (3.331). The values of relative condition factor Kn or the wellbeing for this species were varied from 0.89 to 1.11, with an average of 1.01, showing an ideal growth for the whole population with relatively high values in small and medium size-classes less than 9.0 cm in standard length. The relative growth rate of male's right chelae was varied from 2.63 to 6.3 cm, showing highly positive regression with an increase in standard length, sharply declined to vary between 1.93 and 3.93 cm in females, denotes to relatively weak correlation in females.

Structural damage caused by the invasive crayfish Procambarus clarkii (Girard, 1852) in rice fields of the Iberian Peninsula: a study case

The red swamp crayfish (Procambarus clarkii) is considered one of the most invasive species for aquatic ecosystems. Since its introduction in Spain in 1973, it has spread over different wetlands throughout Western Eu- rope, having rapidly adapted to lakes, ponds and coastal marshes. Among the invaded ecosystems, rice-growing areas have been largely affected by crayfish habits, mainly due to their digging behaviour. In pursuit of this, we at- tempted to draw some patterns about the dynamics of the red swamp crayfish population inhabiting the Ebro Delta Natural Park (NE Spain) - one of the main rice-producing areas within the Mediterranean region - in relation to the structural damage caused to draining structures. More specifically, we aimed at establishing links between the local densities of crayfish, the abundance of burrows they use to shelter, and the intensity of damage involved by crayfish digging activity. For this purpose, two approaches relating crayfish density data with abundances of burrows, com- plemented with in-situ observations of structural damage, were designed. Preliminary results indicated that crayfish density and the number of active burrows were positively related, with higher values implying severe damage to draining structures. However, intense digging activity periods did not directly relate to crayfish density, since other factors were also involved. The information obtained could be useful in planning future surveys in which sound details on digging behaviour and, consequently, the structural damage entailed, could be profitably assessed.

好適なサイズの人工巣穴を用いた外来種アメリカザリガニの駆除効果

好適なサイズの人工巣穴を用いた外来種アメリカザリガニの駆除効果

Rapid Evolution of Antipredator Defenses in Frogs

This study examines how coexistence time shapes antipredator responses of the Iberian water frog (Pelophylax perezi) to the invasive red swamp crayfish (Procambarus clarkii). We collected eggs from five frog populations differing in historical exposure to P. clarkii and raised tadpoles in the presence/absence of caged crayfish. Our results suggest that, while naive P. perezi populations responded behaviorally to P. clarkii, the strong predation pressure imposed by the crayfish has induced the evolution of different antipredator defenses in populations with longer coexistence time. These responses suggest that strong selection by invasive predators may drive rapid evolutionary change in invaded communities.

The influence of environmental factors on abundance and prevalence of a commensal ostracod hosted by an invasive crayfish: are ‘parasite rules’ relevant to non‐parasitic symbionts?

Summary Symbiosis represents a widespread and successful lifestyle, but research on symbiotic associations has been mainly focused on parasites. Three general patterns in parasite ecology have been proposed: (i) aggregation, (ii) positive and tight correlation between mean symbiont abundance and its variance and (iii) positive correlation between abundance and prevalence of symbionts. The factors affecting abundance and prevalence within symbiont species can be grouped into host features and environmental conditions. According to research in parasite ecology, environmental conditions seem to play a minor role. We investigated whether the three most recognised parasite patterns were also evident in a non‐parasitic freshwater ectosymbiont and analysed the effects of host features (sex, body size, density and ecdysis) and environmental conditions (climate and water chemistry) on abundance and prevalence of the symbiont. Our species model was an exotic ectocommensal ostracod, Ankylocythere sinuosa, inhabiting the invasive crayfish Procambarus clarkii in Europe. We sampled 373 crayfish from 26 Spanish localities. We modelled both abundance per occupied host (i.e. intensity) and prevalence using zero‐altered models and a backward model selection of host and environmental variables, and assessed model performance through graphical analyses of Pearson residuals and the relationship between observed and fitted values of the finally selected model. We observed all three parasite patterns in A. sinuosa. Abundance of A. sinuosa was most strongly related to conductivity (negative effect), followed by host density (positive) and ecdysis (negative), with moderate relationships to variables related to water chemistry ( concentration, alkalinity/(Cl− + ) and Cl−/ ratios). Prevalence was related mainly to crayfish density (positive effect) and also to climatic conditions (maximum temperature of warmest month, annual precipitation and precipitation seasonality). Our results suggest that some ‘parasite rules’ may actually be general ‘symbiont rules’. Moreover, our symbiont model was markedly affected by climatic conditions at a regional scale acting on prevalence, and water chemistry at a local level acting on symbiont abundance. This supports the hypothesis of a prominent role of environmental conditions influencing population parameters of non‐parasitic freshwater ectosymbionts. Physiological tolerances to highly unstable environmental factors, together with dependence on highly variable external food sources, probably underlie the high sensitivity to environmental conditions of this category of symbiont.

Ecological consequences of amphibian larvae and their native and alien predators on the community structure of temporary ponds

Summary Connections between consumers and resources in food webs are complex and affect the structure and functioning of ecosystems. We assessed the influence of amphibians as consumers on the structure and functioning of temporary ponds, determining their impact on macrophyte abundance, zooplankton diversity and water chemistry. The effect of amphibians may be modulated by interactions with predators or competitors that alter tadpole density or behaviour. Therefore, we also investigated the consumptive and non‐consumptive effects of native and invasive predators on amphibian larvae and pond ecosystems. High amphibian density decreased macrophyte biomass and zooplankton diversity and increased water turbidity and nutrient content. These effects were largely attributable to tadpoles of the largest herbivorous species, spadefoot toads (Pelobates cultripes). In the absence of spadefoot toads, amphibians unexpectedly affected plant biomass positively. Invasive crayfish (Procambarus clarkii) altered community structure in similar ways to high densities of amphibians and caused greater mortality of amphibian larvae than did native predators. The high herbivorous impact of spadefoot toads and invasive crayfish carried over to the following hydrological cycle.

A New Threat to Groundwater Ecosystems: First Occurrences of the Invasive Crayfish Procambarus clarkii (Girard, 1852) in European Caves

The American red swamp crayfish, Procambarus clarkii, is today the alien species most widespread in European water bodies. This invasive crayfish was found for the first time in some caves of Europe, specifically in Portugal and Italy. The presence of P. clarkii in caves is noteworthy, representing a new threat for the groundwater ecosystems due to the possible negative impacts on the native communities.

Burrowing activity of the invasive red swamp crayfish, Procambarus clarkii, in fishponds of La Brenne (France)

In 2007, the invasive crayfish Procambarus clarkii (Girard 1852) was identified for the first time in the “Parc Naturel Régional de la Brenne” (Indre department, Centre region, France). Ten infestation sites were found in the park, with 62 fishponds colonised. To better understand how the fishponds could be affected, and changes in invaded ponds, we followed crayfish burrowing activity in recently drained fishponds in two areas. Weekly investigations of burrowing activity by analysing their density, occupation and location with respect to the banks, and micro-habitat features were carried out for 2 months in spring. Burrow densities of 1.16 and 1.05 burrows m–2 were found at Le Terrier Blanc and Coudreau 3 respectively. Procambarus clarkii sought humid soil in a dry pond and preferred burrowing on silt substrates. While no statistical differences were found between sites, some differences were observed among weeks independently of the sites. The mean mouth diameter of burrows in the two sites was 5.7 cm (SD = 2.17, n = 214; min. value: 1.2 cm; max. value: 14 cm). Notwithstanding the situation in the last weeks of the study (when most chimneys were built), there was a certain turnover between open and plugged burrows, and in occupancy. Given the scale and duration of the study and the number of fishponds surveyed, this study successfully quantified the dynamics of burrowing in these ponds and conclusions provide a useful basis for future studies and give suggestions of how other colonised fishponds may be affected.

Invasive Crayfish Threaten the Development of Submerged Macrophytes in Lake Restoration

Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard) affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.

How consumption and fragmentation of macrophytes by the invasive crayfish Procambarus clarkii shape the macrophyte communities of temporary ponds

Crayfish are major herbivores in freshwaters, and their activity may change invaded freshwater ecosystems. Macrophyte removal by crayfish results from consumption and fragmentation of plant material and may depend upon the palatability of each species. We studied the impact of Procambarus clarkii on the macrophyte community of Mediterranean temporary ponds, testing in laboratory if consumption and fragmentation of five macrophyte species were correlated in palatability tests and in a preference test. We performed an experiment in a natural pond, where we introduced crayfish and estimated its effects on macrophyte biomass, number of rooted stalks and number of floating cut stalks. P. clarkii consumed preferably Juncus heterophyllus in both tests and avoided Carex divisa and Ranunculus peltatus in the preference test. In the presence of preferred species, consumption and fragmentation of the non-preferred species were heavily reduced. In the field trial, the “Crayfish” compartment had 31% less macrophyte biomass, 41% less rooted stalks and 92% more floating cut stalks. Crayfish may remove macrophyte species from the community sequentially, from the most to the least preferred species. Impacts of crayfish in temporary ponds may depend on time of invasion and on the composition of the macrophyte community.

Differences in refuge function for prey and tolerance to crayfish among macrophyte species

The invasive crayfish Procambarus clarkii is an omnivore and an ecosystem engineer whose feeding mechanism has reduced the abundance of many native invertebrates and macrophytes. Since macrophytes provide refuges for aquatic insects, macrophyte depletion by crayfish might have indirect negative effects on animal prey in aquatic habitats. We postulated that the prey refuges provided by macrophytes and macrophyte tolerance to crayfish cutting and feeding vary among macrophyte species. We conducted two experiments to (1) investigate differences in macrophyte refuge function for dragonfly larvae against crayfish, and (2) test the tolerance to crayfish cutting and feeding among macrophyte species. Elodea nuttallii (submerged plant), Potamogeton crispus (submerged plant), and Carex idzuroei (emergent plant) had greater refuge effects than Trapa japonica (floating-leaved plant), an effect that might result from the larger total cover of E. nuttallii, P. crispus, and C. idzuroei, and the hardness of C. idzuroei leaves. Tolerance to crayfish cutting and feeding was greater in C. idzuroei than in the other species. As the macro-invertebrate assemblages in submerged vegetation are more abundant and species-rich than those in emergent and floating-leaf vegetation, conservation of E. nuttallii and P. crispus should be prioritized for restoring native aquatic animals in ecosystems invaded by the introduced crayfish.

Revisiting reproduction and population structure and dynamics ofProcambarus clarkiieight years after its introduction into Lake Trasimeno (Central Italy)

Key-words: red swamp crayfish, Procambarus clarkii, reproduction, population structure and population dynamics, invasive species Understanding population dynamics and regulation is fundamental for predicting establishment and spread of invasive alien species. In addition, the population biology of invasive alien species offers an opportunity to study basic ecological processes. In this context, we investigated reproductive and growth plasticity in the invasive crayfish Procambarus clarkii in Lake Trasimeno (central Italy). In total, 3153 crayfish were collected monthly from June 2007 to July 2009. The molt status was assessed by evaluating the exoskeleton hardness. To assess the reproductive cycle, the gonado-somatic and wet hepato-somatic indices were calculated for females. The reproductive status of males was appraised as well. We estimated growth and longevity using the von Bertalanffy growth function, and calculated the total, natural and fishing mortality indices. We then compared our present data with those obtained from the same population eight years before. Our results indicate some changes in population dynamics and in both molting and reproductive periods since the initial invasion of the shallow lake investigated. Long-term differences in the life history of the Trasimeno population may be the result of selective pressures different from those of the native range, but may also result from colonization events and human interference caused by professional fishing activities.

Factors affecting the establishment of the invasive crayfish Procambarus clarkii (Crustacea, Decapoda) in the Mediterranean rivers of the northeastern Iberian Peninsula

It is essential to find the combination of factors associated with ecosystem invasibility, as this forms part of basic knowledge on biological invasions and provides important information to guide management and conservation decisions. We surveyed 325 sampling sites in Catalonia to investigate relationships between crayfish presence and a series of biotic and abiotic factors, including fish abundance and species richness, geographical features, and water mineralization and eutrophication. Abiotic data provided by 29 environmental variables were studied by principal-components analysis. We then used a combination of three statistical approaches (comparison of average scores, general linear mixed models, and hierarchical partitioning analysis) to determine the potential relationship between crayfish occurrence and predictors. Our findings seem to indicate that the presence of crayfish was associated with geographical features, water mineralization and eutrophication, and the introduction of non-indigenous fish species to Catalonia. Our results also suggest that re-establishment of the natural hydrology of Mediterranean streams could hinder the spread of Procambarus clarkii. This, combined with preservation of headwater streams and attempts at local extirpation of P. clarkii, would favour native species and, potentially, enable the successful reintroduction of the native white-clawed crayfish (Austropotamobius pallipes species complex).

Complex impacts of an invasive omnivore and native consumers on stream communities in California and Hawaii

The effects of invasive species on native communities often depend on the characteristics of the recipient community and on the food habits of the invasive species, becoming complicated when the invader is omnivorous. In field enclosure experiments, we assessed the direct and interactive effects of an invasive omnivorous crayfish (Procambarus clarkii) and either native herbivorous snails (Physella gyrina) or shrimp (Atyoida bisulcata) on stream communities in California and Hawaii, respectively. Based on literature data and the characteristics of each study site, we predicted that crayfish would affect primarily algal-based trophic linkages in an open California stream but detritus-based trophic linkages in a shaded Hawaiian stream, with trophic cascades mediated through crayfish effects on primary consumers being observed in both systems. As predicted, crayfish in California directly reduced periphyton, filamentous algae, sediment, and snail levels, but generated a cascade by decreasing snail densities and increasing periphyton biomass. Contrary to prediction, crayfish did not reduce total invertebrate biomass. As predicted, crayfish in Hawaii reduced leaf litter, filamentous algae, and benthic invertebrate biomass. Contrary to our predictions, however, a trophic cascade was not observed because shrimp did not affect periphyton levels, crayfish did not reduce shrimp abundance, and crayfish had greater negative impacts on filamentous algae than did shrimp. Our findings highlight that the same invasive species can generate different effects on disparate systems, probably as mediated through the availability of different food types, flexibility in the invasive species' food habits, and complex pathways of trophic interaction.