Crayfish Species Research Articles

Does the narrow-clawed crayfish, Pontastacus leptodactylus (Eschscholtz, 1823) (Decapoda: Astacidea: Astacidae), contributes to the decline of the noble crayfish, Astacus astacus Linnaeus, 1758 in the Belarusian Lakeland?

Abstract The noble crayfish, Astacus astacusLinnaeus, 1758, is the rarest crayfish species in Belarus, distributed mainly within the Belarusian Lakeland, a region of numerous lakes of glacial origin in northern Belarus. The territory has been surveyed for the species to recognize its conservation status. From a total of 44 previously known A. astacus habitats, the species now occurs in 23 of them, five of which cohabit with the narrow-clawed crayfish, Pontastacus leptodactylus (Eschscholtz, 1823) which occupies the majority of habitats where A. astacus populations have been lost. Based on the long-term capture data, we tracked the displacement of A. astacus by P. leptodactylus in Karavaino Lake. To our knowledge, this observation represents the first published field evidence showing the progressive and successful outcompeting of A. astacus by P. leptodactylus. Based on our results, as well as by comparing it with previously published information on the crayfish distribution in Belarus, we highlight the unrealised scale of P. leptodactylus expansion in its non-native area of occurrence in Belarus. Due to the invasive potential of P. leptodactylus, we stress the need for research on the influence of P. leptodactylus on overall biodiversity within its introduced range.

Habitat alters biogeographical and evolutionary patterns of body size in freshwater crayfishes

Abstract Biogeographical patterns explain variation in body size, although the strength and directions of these patterns vary. When researchers account for the micro- or macrohabitats that species inhabit, they often find that biogeographical relationships with body size are modified, especially in taxa that inhabit diverse environments. Freshwater crayfishes are an ideal group in which to study the interaction between habitat, biogeography, and body size, because there are >700 crayfishes that inhabit aquatic environments, semi-terrestrial burrows, and caves. Here, we explore evolution of body size across 452 species of crayfish by considering the interaction between their habitats (aquatic, semi-terrestrial/aquatic, semi-terrestrial, and cave-dwelling) and the mean temperature of their geographical range. We documented 64-fold variation in body length. Aquatic species were the largest and had the greatest variation in body size. Crayfishes that inhabit both semi-terrestrial and aquatic habitats exhibit a weak negative relationship between body size and environmental temperature; solely aquatic species reverse this relationship. Evolutionarily, our ancestral reconstruction suggests that the ancestral crayfish was an aquatic species with a body length of 81.1 mm, which aligns with data from fossil crayfish. Overall, our study highlights how uniting biogeographical and evolutionary approaches improves our ability to explore patterns of animal body size and unearth explanatory mechanisms.

Relationships between crayfish population genetic diversity, species richness, and abundance within impounded and unimpounded streams in Alabama, USA.

Understanding the relationship between multi-scale processes driving community- and population-level diversity can guide conservation efforts. While the importance of population-level genetic diversity is widely recognized, it is not always assessed for conservation planning, and positive correlations with community-level diversity are sometimes assumed, such that only the latter is measured. We surveyed species richness and cumulative multispecies abundance of crayfishes in impounded and unimpounded streams in the southern Appalachian Mountains (Alabama, USA). We simultaneously assessed levels of population genetic diversity within two focal crayfishes (Faxonius validus and F. erichsonianus) using nuclear (nDNA; inter-simple sequence repeat (ISSR)) and mitochondrial DNA (mtDNA; mitochondrial DNA cytochrome oxidase subunit I (mtCOI)) markers. We then tested for species-genetic diversity correlations (SGDCs), species diversity-abundance correlations (i.e., more individuals hypothesis, MIH), and abundance-genetic diversity correlations (AGDCs) across sites. We also examined the relationship between each of the three different types of correlation (i.e., species richness, cumulative multispecies abundance, and population genetic diversity) and stream habitat characteristics and fragmentation. Surprisingly, based on F. validus mtDNA data, sites with the greatest multispecies abundance had the lowest genetic diversity, indicating a negative AGDC. However, no AGDC was evident from nDNA. There was no evidence of SGDCs for F. validus based on either of the two genetic data types. For F. erichsonianus, there was no evidence for SGDC or AGDC. When considering the community-level data only, there was no support for the MIH. Stream width was positively correlated with F. validus genetic diversity, but negatively correlated with multispecies abundance. Similarly, species richness was positively correlated with stream width in unimpounded streams but negatively correlated with width in impounded streams. These findings indicate that community-level diversity cannot be indiscriminately used as a proxy for population-level diversity without empirically testing this correlation on the focal group. As such, community- and population-level assessments for multiple crayfish species are needed to better understand drivers of diversity and eco-evolutionary processes which will aid in the conservation of this vulnerable taxonomic group.

Escape rooms: behavioural response of two invasive crayfish species under water decline scenarios

Climate change and invasive alien species pose a significant threat to biodiversity and the survival of native species. This study considered the impact of drought conditions on the escape behaviour through terrestrial dispersal ability of two invasive freshwater crayfish species, the red swamp crayfish (Procambarus clarkii) and signal crayfish (Pacifastacus leniusculus). Using an experimental design simulating drought conditions and Mediterranean summer temperatures, we tested the hypothesis that P. clarkii exhibits a greater tendency to terrestrial migration and a higher land-walking speed than the P. leniusculus. The results indicated that both species demonstrated strong escape behaviour, with P. clarkii showing escape success higher than P. leniusculus, and increasing with decreasing mean night temperature and crayfish weight. Although drought conditions did not trigger escape, invasive species showed increased resistance and the ability to move to more favourable environments, suggesting that drought is not an effective geographic barrier against the spread of these species. These results underline the importance of considering invasive species' ability to escape and climb as part of management and control strategies.

Integrating aquatic species, assemblage, and habitat climate change vulnerabilities into a watershed-scale decision support framework

Climate change is increasingly recognized as a serious threat to ecological systems, particularly freshwater systems. As a result, climate adaptation planning is more common in natural resource management. Because conservation resources are limited, decision support tools can help managers prioritize actions. We created the Species and Habitat-based Ecological Decision Support tool (wtrSHEDS) for conservation managers by integrating two distinct indices: one biologically based on aquatic watershed-scale species assemblages and the other a habitat climate change vulnerability index. To do this, we evaluated 60 crayfish and fish species in West Virginia, USA, using the NatureServe Climate Change Vulnerability Index under an A1B emissions scenario. The species vulnerability assessment results indicated that most species we assessed are vulnerable to climate change. Four species of fish and two species of crayfish had extremely high vulnerability due to their dependence on a specific hydrological cycle, sensitivity to barriers, and reproductive dependence on a thermal niche. Aggregating species at the watershed scale (8-digit hydrological unit code [HUC]) using an adapted weighted sum indicated which assemblages were the most and least vulnerable to climate change. Secondly, we created a unique habitat vulnerability index using the established Northeast Association of Fish and Wildlife Agencies habitat vulnerability index and an index of land cover vulnerability from the Forecast Scenario model’s land cover change projections under the A1B emissions scenario to incorporate potential synergistic impacts of land use. Land cover projections were reclassified based on the assumption that developed land would have a higher potential to interact with climate change than forested lands synergistically. We combined the two habitat indices at the watershed scale (HUC 8) and performed a Hot Spot Analysis to 1) combine the assemblage and habitat vulnerability indices and 2) identify watersheds of conservation priority. This assessment methodology illustrates a means of identifying priority conservation areas in West Virginia that utilize pre-existing data, can be modified to suit management needs, and, therefore, one that managers across regions can readily apply to their system.

Beneath the surface: two new burrowing crayfish species of Parastacus Huxley, 1879 (Malacostraca, Decapoda, Parastacidae) from the Mirim-São Gonçalo Basin, southern Brazil

Abstract In this contribution, we describe two new species of burrowing crayfish from the countryside of the municipality of Pelotas in the south region of the state of Rio Grande do Sul, southern Brazil. We evaluated morphology and also their conservation status according to the IUCN Red List Criteria. Parastacus schubarti sp. nov. differs from the burrowing species of Rio Grande do Sul state in having an epistome anteromedian lobe septagonal, areola wide, and by the large spines in telson lateral margins. Parastacus dincaoi sp. nov. is distinguishable from the burrowing species of Rio Grande do Sul state in having a wide pleon and a subtriangular telson with small blunt spines on lateral margins. The extent of occurrence of P. schubarti sp. nov. and P. dincaoi sp. nov. were estimated at 382 km2 and 963 km2, respectively. The main threats identified were continued decline in the habitat quality, resulting from deforestation, habitat fragmentation, agriculture and livestock. However, as we currently know only one point of occurrence for each new species, we suggest that both be categorized as Data Deficient.

The chromosome-level genome assembly of the red swamp crayfish Procambarus clarkii

Red swamp crayfish, Procambarus clarkii, is the most cultured freshwater crayfish species. It attracts significant research attention due to its considerable economic importance. However, the limited availability of genome information has impeded further genetic studies and breeding programs. By utilizing Illumina, PacBio, and Hi-C sequencing technologies, we present a more comprehensive and continuous chromosome-level assembly for P. clarkii than the published one. The final genome size is 4.03 Gb, consisting of 2,358 scaffolds with a N50 of 42.87 Mb. Notably, 3.68 Gb, corresponding to 91.42% of the genome, was anchored to 94 chromosomes. The assembly comprises 70.64% repetitive sequences, including 5.21% tandem repeats and 65.40% transposable elements. Additionally, a total of 4,456 non-coding RNAs and 28,852 protein-coding genes were predicted in the P. clarkii genome, with 96.26% of the genes were annotated. This high-quality genome assembly not only represents a significant improvement for the genome of P. clarkii and provides insights into the unique genome evolution, but also offers valuable information for developing freshwater aquaculture and accelerating genetic breeding.

The Impacts of Invasive Crayfish and Other Non-Native Species on Native Freshwater Crayfish: A Review.

Freshwater crayfish are vital species in ecosystems where they naturally occur, as they hold keystone and ecological engineering positions in these systems. Non-native species are common and widely spread throughout Earth's freshwater ecosystems and can have severe impacts on native crayfish populations. There has yet to be a comprehensive global review of the impacts of non-native species on native crayfish. Two literature searches were conducted using Web of Science and Google Scholar to find articles to address four key aims: (1) summarise trends in the literature; (2) examine the mechanisms by which invasive crayfish impact native crayfish species; (3) examine the mechanisms by which other non-native species, such as fish, impact native crayfish species; and (4) identify gaps in knowledge and research priorities. This review highlights that a far greater amount of research has addressed the effects of invasive crayfish than other non-native species. The research on invasive crayfish focuses on four types of interactions with native crayfish: competition, predation, introduction of disease, and reproductive impacts. Studies addressing the impacts of other non-native species on crayfish indicate that predation and habitat destruction by these species are the key processes impacting native crayfish. It is evident that field-based research, particularly concerning competition between invasive and native crayfish, is limited. Therefore, further in situ research is needed to assess the validity of laboratory results in a natural setting. Additionally, in many cases, the impact of certain non-native species on native crayfish populations has gone unmonitored. For this reason, it is recommended that additional research focus on assessing the impact of these non-native species. To conclude, the impacts of invasive crayfish on native crayfish are profound and wide-ranging, often leading to population decline or extirpation. Further, other non-native species are also likely to have a highly deleterious impact on native crayfish populations; however, more research is required to understand the scope of this impact.

Characterising dispersal and potential impacts of non‐native red swamp crayfish (Procambarus clarkii) populations in the coastal plain region of the pee Dee River basin, U.S.A.

Abstract Non‐native species can spread rapidly through aquatic ecosystems in association with both natural and anthropogenic mechanisms, but the relative importance of these two mechanisms in determining the spread of a species is not always clear. The red swamp crayfish (Procambarus clarkii) has been introduced to multiple continents, including waterbodies in the United States where both natural and anthropogenic dispersal are likely to have contributed to its current distribution. The present study combined comparisons of historical and contemporary distributions of P. clarkii and several high conservation priority crayfish species, regional field sampling, and microsatellite‐based genetic approaches from the Pee Dee River basin in North Carolina and South Carolina to understand the dispersal patterns of P. clarkii and its potential effects on native crayfishes. Field sampling and microsatellite analyses revealed widespread populations of P. clarkii throughout the study area with catchment‐specific patterns of population genetic structure, wherein more distinct genetic structures were found in the basin with historic aquaculture activities and a longer period of occurrence. The rapid spread of P. clarkii has occurred concurrently with extirpations of populations of native crayfishes, namely the Waccamaw crayfish (Procambarus braswelli), the Carolina Sandhills crayfish (Procambarus pearsei) and the coastal plain crayfish (Procambarus ancylus). The rapid spread of P. clarkii and coincident extirpation of native crayfishes calls for more extensive regulatory controls to help prevent the intentional or accidental release of non‐native crayfishes through aquaculture practices, bait releases, the pet trade and the environmental education industry.

Effect of feed and holding conditions on survival and growth of juvenile crayfish Pontastacus leptodactylus and Faxonius limosus

Abstract In the European natural environment attempts are undertaken to replace invasive crayfish species with native ones. For this purpose, aquaculture of crayfish is required, but their behaviour and the lack of balanced feeds impede further development. To effectively eliminate invasive crayfish, more knowledge is needed, in context of their similarities and differences from native species. This study investigates two crayfish species, native Pontastacus leptodactylus and invasive Faxonius limosus in relation to different holding conditions and feeds. Juvenile crayfish were exposed to two types of holding conditions, inside (IN) in tap water and outside (OUT) in water with natural plankton content. In addition, three feeds were tested, sinking chips (F1), flakes (F2) and floating sticks (F3). The feeds composition was similar, but sinking times differed and were quick for F1 and slow for F2 and F3, which provided extended visual and chemical exposure to crayfish. The significant effect of holding conditions on survival was found for both species, with highest results for OUT holding conditions, suggesting important role of natural plankton in survival. Three feeds (F1, F2 and F3), showed no effect for P. leptodactylus but F2 and F3 improved growth in F. limosus, indicating more efficient utilisation of the detected feed.

Prevalence of the crayfish plague pathogen in red swamp crayfish populations in western France: How serious is the risk for the native white-clawed crayfish?

The crayfish plague pathogen Aphanomyces astaci has been implicated in a number of mass mortalities and irreversible population declines of native crayfish across Europe. At present, the reservoirs of the pathogen in Europe are mainly populations of invasive North American crayfish species. In southwestern Europe, including France, a particularly widespread invader is the red swamp crayfish Procambarus clarkii. Recent distribution data confirm that P. clarkii is present in at least 75 French departments, i.e. more than 78% of those in metropolitan France. We analysed the prevalence and pathogen load of A. astaci in 42 populations of this species in western France (Nouvelle Aquitaine region), where the species is most densely distributed, particularly in a wide range of environments around the Gironde estuary. The pathogen was detected by two different quantitative PCR assays in more than three quarters of the populations studied (34 out of 42); 163 out of 480 analysed crayfish individuals tested positive for the presence of A. astaci. In most cases, individual infection levels were very low, detectable with quantitative PCR but not sufficient for pathogen genotyping. In seven P. clarkii individuals from four populations, however, we were able to assess A. astaci variation by microsatellite markers and sequencing of mitochondrial markers. All these host specimens carried A. astaci genotype group D, haplotype d1, which has caused the majority of crayfish plague outbreaks in neighbouring Spain. In contrast, the French outbreaks genotyped to date (including eight newly analysed in this study) were mostly caused by strains of genotype group B, specific to the signal crayfish Pacifastacus leniusculus. Haplotype d1 found in P. clarkii was involved in one of the newly characterised outbreaks. Our study confirms that P. clarkii is a potentially important reservoir of the crayfish plague pathogen in France, but not the main source of the pathogen in mass mortalities of A. pallipes, probably due to different ecological requirements of the different invasive host crayfish. However, as P. clarkii continues to spread, the threat posed by this species to native crayfish is likely to increase.

An old unknown: 40 years of crayfish plague monitoring in Switzerland, the water tower of Europe

The oomycete Aphanomyces astaci is the causative agent of crayfish plague, a disease threatening susceptible freshwater crayfish species in Europe.To detect its spatiotemporal occurrence in Switzerland, we reviewed (1) the literature regarding occurrence of crayfish plague and North American crayfish carrier species and (2) the necropsy report archive of the Institute for Fish and Wildlife Health (FIWI) from 1968 to 2020. In the past, crayfish plague was diagnosed through several methods: conventional PCR, culture, and histology. When available, we re-evaluated archived Bouin’s or formalin-fixed, paraffin-embedded samples collected during necropsies (1991–2020) with a recently published quantitative PCR.Literature research revealed putative reports of crayfish plague in Switzerland between the 1870s and 1910s and the first occurrence of three North American crayfish species between the late 1970s and 1990s.Finally, 54 (28.1%) cases were classified as positive and 9 (4.7%) cases as suspicious. The total number of positive cases increased by 14 (14.7%) after re-evaluation of samples. The earliest diagnosis of crayfish plague was performed in 1980 and the earliest biomolecular confirmation of A. astaci DNA dated 1991. Between 1980–1990, 1991–2000 and 2001–2010 crayfish plague spread from one to two and finally three catchment basins, respectively.Similar to other European countries, crayfish plague has occurred in Switzerland in two waves: the first at the end of the 19th and the second at the end of the 20th century in association with the first occurrence of North American crayfish species. The spread from one catchment basin to another suggests a human-mediated pathogen dispersal.

High variation of virulence in Aphanomyces astaci strains lacks association with pathogenic traits and mtDNA haplogroups

Introduced into Europe from North America 150 years ago alongside its native crayfish hosts, the invasive pathogen Aphanomyces astaci is considered one of the main causes of European crayfish population decline. For the past two centuries, this oomycete pathogen has been extensively studied, with the more recent efforts focused on containing and monitoring its spread across the continent. However, after the recent introduction of new strains, the newly-discovered diversity of A. astaci in North America and several years of coevolution with its European host, a new assessment of the traits linked to the pathogen’s virulence is much needed. To fill this gap, we investigated the presence of phenotypic patterns (i.e., in vitro growth and sporulation rates) possibly associated with the pathogen’s virulence (i.e., induced mortality in crayfish) in a collection of 14 A. astaci strains isolated both in North America and in Europe. The results highlighted a high variability in virulence, growth rate and motile spore production among the different strains, while the total-sporulation rate was more similar across strains. Surprisingly, growth and sporulation rates were not significantly correlated with virulence. Furthermore, none of the analysed parameters, including virulence, was significantly different among the major A. astaci haplogroups. These results indicate that each strain is defined by a characteristic combination of pathogenic features, specifically assembled for the environment and host faced by each strain. Thus, canonical mitochondrial markers, often used to infer the pathogen’s virulence, are not accurate tools to deduce the phenotype of A. astaci strains. As the diversity of A. astaci strains in Europe is bound to increase due to translocations of new carrier crayfish species from North America, there is an urgent need to deepen our understanding of A. astaci’s virulence variability and its ability to adapt to new hosts and environments.

Variation in fine-scale water table depth drives abundance of a unique semi-terrestrial crayfish species.

With anthropogenic changes altering the environment and the subsequent decline of natural habitats, it can be challenging to predict essential habitats for elusive and difficult to study taxa. Primary burrowing crayfish are one such group due to the complexity in sampling their semi-terrestrial, subterranean habitat. Sampling burrows usually requires a labor-intensive, time-consuming excavation or trapping process. However, limited information on burrowing crayfish suggests that fine-scale habitat variation may drive burrowing crayfish habitat choice. This project aimed to evaluate the fine-scale habitat characteristics that influence burrowing crayfish presence and abundance at a large, restored-remnant grassland preserve in north-central Illinois. We documented burrow abundance and quadrat-specific habitat variables such as root biomass, canopy cover, apparent seasonal high-water table (water table) depth and dominant vegetation at sites with and without burrowing crayfish populations. Data was recorded at every quadrat and analyzed using generalized linear mixed models. A total of 21 models were created to determine what habitat variables affected burrow presence and abundance. We found that the water table depth was a significant driver of burrow presence and abundance. Root biomass and vegetation cover were not significant drivers, although they did show up in the final models, explaining the data. These findings demonstrate empirical support for previous observations from other burrowing crayfish research and demonstrate the influence of fine-scale habitat when modeling elusive taxa requirements.

Assessing Reliability for Quantifying Social Interactions among Crayfish

Animal behavior is a useful way to evaluate the environment and can be a predictive tool to assess not only the effects of treatments in a laboratory setting, but also the status of ecological habitats. As invasive species of crayfish encroach on territories of native species, the social behaviors and interactions can be informative for ecological studies. For a wider and more impactful effect, training community scientists using a scoring system to record the social interactions of crayfish that includes both the level of aggression and intensity would provide useable data to monitor the environment. Amateur scientists with little training were fairly reliable in their average scoring of the crayfish and the maximum behavior score with an expert as well as among themselves. However, the number of interactions was not as a reliable metric to compare with the expert or just among the amateurs.

Environmental DNA can inform the trade‐off between proactive and reactive strategies for crayfish conservation

AbstractThe introduction of the signal crayfish Pacifastacus leniusculus to British rivers has led to ecological degradation and the decline of the native white‐clawed crayfish Austropotamobius pallipes. To manage and mitigate the impact of the signal crayfish, conservation agencies and government bodies employ multiple conservation strategies. These take the form of proactive native crayfish breeding and stocking programs and reactive invasive crayfish control programs. Here, we used eDNA to assess the populations of native and invasive crayfish species across 50 sites in 10 river catchments in Norfolk, United Kingdom (UK). The sites were chosen to enable assessment of the potential of eDNA to inform proactive and reactive crayfish conservation strategies. Three of the catchments sampled were selected to assess the success of recent A. pallipes reintroduction, whereas the remaining seven were selected to better understand the distribution of each species at the landscape scale. Combining results of eDNA‐based methods with net searches within an occupancy model enabled us to confidently determine the presence of P. leniusculus at eight sites, and A. pallipes at three sites, which was more than visual searches alone (five and two study sites, respectively). Neither eDNA nor net searches detected A. pallipes at sites where A. pallipes had been reintroduced. We recommend that practitioners using eDNA‐based surveys for management and conservation of crayfish should consider: (1) designing eDNA surveys with an emphasis on large spatial scales to comprehensively describe the distributions of native and invasive crayfish in a region of interest; (2) work with local conservation organizations and/or government bodies to inform the selection of study sites to generate results that are meaningful to real‐world conservation actions; and (3) use results from eDNA‐based crayfish surveys to target limited conservation resources to appropriate proactive and/or reactive conservation actions.

Species-specific trophic discrimination factors can reduce the uncertainty of stable isotope analyses

Stable isotope analysis has been broadly used to study food webs, but often relies on inaccurate assumptions of trophic isotopic discriminations, which could lead to misinterpretation of obtained results. While many taxa exhibit similar trophic discrimination factors (TDFs), crayfish, exhibit omnivorous feeding strategies, yet TDFs are missing. In this study, we determined TDFs and tissue biokinetic parameters of the marbled crayfish Procambarus virginalis as a model species. Moreover, we compared commonly used TDFs and those determined from this study and applied them across species and ecosystems as a first attempt to compare the effect of species-specific TDFs in Bayesian trophic mixing models. Our results revealed differences between the TDFs of different tissues and biokinetic parameters of crayfish. Our result also revealed TDFs differences between crayfish relying mostly on plants versus those relying on an animal diet. We found differences of TDF suitability among species and ecosystems, highlighting the need for specific TDFs for different crayfish species. This study improves our understanding and the need for species-calibrated TDFs for robust statistical analysis of stable isotope data. Our approach is widely applicable across taxa and ecosystems to reduce the bias introduced by using unspecific TDFs in Bayesian mixing models.

Crayfish communities converge over succession in beaver pond metacommunities

Abstract Metacommunity theory predicts that the relative importance of regional and local processes structuring communities will change over ecological succession. Determining effects of these processes on taxonomic and evolutionary diversity in spatially structured freshwater habitats of different successional stages may greatly improve understanding of the maintenance of diversity across temporal and spatial scales. In this study, we evaluated crayfish diversity at local and regional scales in pond metacommunities undergoing secondary succession from beaver (Castor canadensis) disturbance. Following theoretical predictions from metacommunity ecology of the increasing importance of local processes over succession, we hypothesised a decline in crayfish local and β diversity over succession from stronger local structuring as the older ponds may provide less suitable habitat than streams. Crayfish species and phylogenetic diversity were evaluated in beaver pond metacommunities and reference headwater streams located in three catchment regions. DNA sequences from the mitochondrial cytochrome oxidase I gene were used to assign crayfish to species for community and phylogenetic diversity tests. Local and β diversity were contrasted across beaver ponds ranging in age from 24 to 70 years and as a function of metacommunity processes. Counter to predictions, local species diversity among streams and the successional stages of ponds categorised by age class (24–39 years; 42–57 years; 60–70 years) did not differ, but community and phylogenetic convergence occurred in the oldest pond ecosystems. Crayfish community composition differed between the youngest and oldest ponds, resulting from higher abundance in the youngest ponds and community convergence in the oldest ponds. The association between community composition and the environment was strongest in streams and decoupled with pond age. In contrast, the correlation between intraspecific haplotype composition and the environment increased over succession. Among the three metacommunities, the regional crayfish species diversity arose from a combination of the temporal and environmental drivers from beaver‐constructed ecosystems and dispersal limitation within catchments. This study represents the first investigation of the taxonomic and phylogenetic diversity response to the successional stages of beaver pond metacommunities. The detection of differential crayfish composition and haplotype sorting to pond age suggests a role for local structuring and further indicates that future studies should acknowledge succession in shaping species diversity at local and regional scales. Dispersal limitation within catchment regions probably contributes to the evolution of crayfish species diversity in metacommunities and the overall maintenance of biodiversity. The results support a transition in community and freshwater ecology from a recent emphasis on spatial processes towards the integration of temporal drivers to better identify regulators of taxonomic and phylogenetic diversity across scales.

Biological indicators and commercial exploitation of main fish and river crayfish species of the Zaporizhzhia (Dnipro) reservoir

Aim: To analyze and summarize the biological indicators of the main industrial fish and river crayfish species in the Zaporizhzhia (Dnipro) reservoir under conditions of fishery exploitation. Methods: Biological analysis of fish was conducted according to classical methods in ichthyology, using the following parameters: standard and absolute body length, individual mass, gender, feeding coefficient. Crayfish, caught in fishing gear, underwent morphometric measurements to determine individual mass and gender. Biological sampling was carried out during the vegetation period of 2023 during both control and commercial fishing in the Zaporizhzhia (Dnipro) reservoir at three sites differing in hydrology and degree of anthropogenic impact. Research results: According to the data from the Department of the State Agency of Reclamation and Fisheries Management in Dnipropetrovsk Oblast, during 2023, 140,504 tons of fish were caught in the Zaporizhzhia (Dnipro) reservoir, nearly 8 times less than in 2021. In 2021, 1078.25 tons of aquatic resources were caught, which is 8 % less than in 2020. Silver carp was the dominant fish species in 2022, accounting for 80.5 % of the total catch in the reservoir. Herbivorous fish species accounted for 5.4 % of the catch, roach - 3.3 %, bream - 2.3 %, perch - 2.0 %. Based on the conducted research, recommendations have been provided regarding the establishment of forecasts and limits for the extraction of aquatic resources from the Zaporizhzhia (Dnipro) reservoir for the year 2024. Conclusions: The Zaporizhzhia (Dnipro) reservoir has potential for the development of fishing, fish farming, and aquaculture in the Prydniprovsky region. The research results suggest that limits can be set on the catch of certain fish species: bream- up to 210 tons, pike-perch - up to 42 tons, roach - up to 350 tons, and perch - up to 138 tons. However, the catch of silver carp, bleak, sprat, herbivorous fish, and sun-perch is recommended to be unrestricted. The forecasted catch of crayfish is within 1 ton. The catch of other aquatic resources should also be conducted within forecasted levels

Prevalence of white spot syndrome virus (WSSV) in wild-caught and commodity decapod crustaceans in coastal South Carolina, USA

Abstract White spot syndrome virus (WSSV) is a highly contagious and economically costly virus that affects many crustacean species. Since its introduction into the United States in the 1990s, it has spread from aquaculture shrimp and crayfish to wild crustaceans throughout the southeastern United States. Transmission to natural systems may occur through contact between commodity (i.e., store-bought) and wild crustaceans or the use of infected frozen shrimp as bait, which has been proven capable of transmitting the virus. In this study, we surveyed both live (Penaeus setiferus (Linnaeus, 1767) and P. aztecusIves, 1891) and frozen commodity shrimp (Penaeus vannameiBoone, 1931) and crayfish (Procambarus troglodytes (Le Conte, 1856) and P. clarkii (Girard, 1852)) as well as wild populations of some of these species of shrimp, crayfish, and blue crabs (Callinectes sapidusRathbun, 1896) in South Carolina for WSSV. We found extremely low levels of the virus in wild-caught decapods but high levels of WSSV in commodity crayfish (50%) and imported frozen shrimp (43.3%). While additional work is needed to understand the environmental conditions that affect the transmission potential of WSSV, these results suggest that care must be taken with commodity crustaceans to prevent introductions of WSSV and subsequent harm to natural ecosystems.