This study reviews the introduction history and distribution of alien freshwater crayfish in Taiwan through literature surveys, morphological examination of preserved specimens, and field surveys. Since the 1970s, multiple non-native crayfish species have been introduced mainly for ornamental, culinary, and aquaculture purposes, but their status has been poorly documented. The introduction of alien freshwater decapods began in 1970 with large freshwater prawns (Macrobrachium spp.). In the 1980s, the red swamp crayfish, Procambarus clarkii, was introduced and established in the wild. The 1990s saw introductions of the Australian redclaw, Cherax quadricarinatus, and yabby, Cherax destructor, for aquaculture trials. Morphological observations of wild P. clarkii specimens and absence of branchiobdellidan ectosymbionts—typical in Japanese populations—suggest a possible Japanese origin, though alternative explanations exist, warranting genetic confirmation. Field surveys revealed an established population of C. quadricarinatus in the Mudan River system, likely due to escapes from aquaculture and pet releases. Research on alien crayfish in Taiwan is developing, with increasing graduate level studies. This review clarifies their introduction history and distribution, providing fundamental data for fisheries management and invasive species control.
We report the first confirmed occurrence of Cambaroides wladiwostokiensis Birstein & Vinogradov, 1934 in China, based on field surveys conducted between 2015 and 2024 in the Upper Morin and Suifun River basins. A total of 78 individuals were collected, and 62 adult specimens were examined in detail. This study presents the first comprehensive morphological description of the species from China, supplementing previous accounts that lacked dissection-based analyses. Diagnostic traits distinguishing C. wladiwostokiensis from sympatric congeners (C. dauricus, C. schrenckii) are clarified. Historical records were critically reassessed, and several misidentifications and ambiguous locality data were corrected. Additionally, our surveys documented local extirpations of C. dauricus and C. similis in parts of northeastern China. Major threats to native populations include habitat degradation, water pollution, and unregulated exploitation. Although C. wladiwostokiensis persists in some protected areas, its longterm survival is threatened by invasive species. This study highlights the urgent need for conservation measures targeting native East Asian crayfish and provides essential morphological and ecological data to support future monitoring and management strategies.
The invasive White River crayfish, Procambarus acutus (Girard, 1852), has recently been reported from several regions of central Ontario, Canada through the online platform, iNaturalist as well as the Invading Species Awareness Program. Between September 2022 and September 2025, we conducted surveys to confirm these reports. Our results show that P. acutus is now established and reproducing in the Severn Sound region where we collected a female with eggs and reports of females carrying young and freelivingyoung of the year have been posted on iNaturalist since. In 2024, a report of suspected P. acutus in Oakbank Pond in Thornhill, Ontario was confirmed by subsequent surveillances resulting in multiple captures from burrows in ditches near the pond, including a female carrying young. Our observations indicate the species is established and surviving in and around the pond and poses a risk of invasion into the headwaters of the Don River, one of the major tributaries to Lake Ontario. Our study confirms the presence and establishment ofP. acutus in the Port Severn region, as well as Oakbank Pond in Thornhill, and expands the distribution ofthis species in Ontario and, as a result, Canada. Copyright (c) 2025 by The Author(s). Published by the International Association ofAstacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This study documents new aspects of the distribution, ecology, and conservation of the smooth crayfish, Euastacus girurmulayn Coughran, 2005, a dwarf freshwater crayfish endemic to rainforest headwater streams of northeastern New South Wales. Field surveys extended its known distribution from the Wilsons River system to include the Tweed and Brunswick River basins and the Cudgera Creek drainage, increasing the extent of occurrence (EOO) to 200.7 km2 and area of occupancy (AOO) to 60 km2. The species is a habitat specialist confined to shaded, permanently flowing upper catchment streams between 59-718 m in elevation. New records provide the first detailed observations of fecundity, confirm a maximum size of 34.7 mm OCL, and extend its altitudinal range. Molecular analyses validated the distinctiveness of E. girurmulayn and revealed marked divergence among populations, indicating the presence of distinct evolutionary significant units (ESUs). Major threats include climate change, high-intensity bushfires, drought, habitat loss, invasive species, illegal collection, and potential disease introduction. These findings support the recent listing of E. girurmulayn as Endangered under the EPBC Act (criteria B1ab(iii, v)) and highlight the urgent need for targeted conservation actions to ensure the persistence of this highly range-restricted species. Copyright (c) 2025 by The Author(s). Published by the International Association ofAstacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
In this study the reproduction of the southernmost Italian population of the invasive Pacifastacus leniusculus (Dana, 1852) was analyzed. The species was recorded for the first time in the Clitunno River in 2020, an eradication plan started in June 2022 as part of the LIFE IMAGINE 19 IPE/IT/000015 project and aspects of the reproductive biology were examined from individuals captured. In this population, gonad maturation starts in February in females and in May in males. Spawning begins in October and the incubation lasts approximately four-five months. The smallest ovigerous female recorded had a cephalothorax length (CL) of 3.3 cm at an estimate age of 2+. Ovarian eggs and pleopodal eggs number ranged from 142 to 726 and from one to 481, respectively. A positive significant linear correlation between ovarian egg number and female CL was observed. Pleopodal egg diameter was positively correlated with female CL, indicating that bigger females produce larger eggs. This study shows the species is well adapted to the environmental conditions of the new habitat, exhibiting early sexual maturity, and a high potential fecundity but with a high percentage of egg loss. The reproductive characteristics highlighted in this study could help optimize containment efforts for the signal crayfish. Copyright (c) 2025 by The Author(s). Published by the International Association of Astacology This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Accurate IUCN Red List of Threatened Species assessments for European crayfish continue to be constrained by fragmented distribution data, scarce documentation ofpopulation spatial dynamics, and unresolved taxonomy within several species complexes. Although robust analytical tools now exist to quantify occurrences, range metrics, temporal dynamics, and fragmentation patterns, their effectiveness ultimately depends on the availability of a harmonized and comprehensive evidence base, which the astacological community has yet to assemble for high-confidence conservation assessments. Using contrasting case studies, here I show that assessment quality depends directly on data completeness, integration, and taxonomic clarity. I outline the technical infrastructure now available to support transparent and reproducible analyses and argue for a coordinated effort to consolidate the evidence underpinning Red List assessments. With such contributions in place, conservation evaluations can move beyond reflecting evidence gaps and instead more accurately capture biological reality regardless of how urgent updates are needed thereby enhancing their policy relevance. Although focused on Europe, the principles presented here offer a scalable model for crayfish conservation worldwide. Copyright (c) 2025 by The Author(s). Published by the International Association ofAstacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Nail polish (paint) is a noninvasive, inexpensive external crayfish marking method for shorter-term studies (i.e, 30-90 d); however, retention time is seldom reported. Our objectivewas to estimate retention time of two nail-polish types (gel and lacquer) in a probabilistic framework using red swamp crayfish Procambarus clarkii. We marked the carapace of 90 crayfish with six different bottles (treatments) of each type in an indoor raceway that mimicked natural habitat. We estimated nail-polish retention probability using a variation of a known-fate survival model. This approach retained information for crayfish that either molted or died prior to losing the mark (a minimum retention time). Both types had a >0.90 30 d and a >0.80 60 d retention probability. On average, 90 d retention was-0.75 and-0.65 for gel and lacquer, respectively. There was more variability in retention among treatments for gel. There was no retention relationship with carapace length. Males had-0.05 higher mean retention than females. We found that both gel and lacquer nail polish were effective a shorter-term crayfish studies, though gel may be preferred for field studies due to its quicker drying time. Our study framework is applicable to any mark-retention study where individuals perish, molt, or otherwise go unseen. Copyright (c) 2025 by The Author(s). Published by the International Association of Astacology This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The objectives of our article are to describe causalities on the impact on crayfish from introduction of the oomyceteAphanomyces astaci (Shikora) to Europe and to explore possibilities to govern and improve the situation for Astacus astacus (Linn & eacute;) through establishment of production of renewable energy. The anthropegenic spread ofA. astaci is driven by the introduction of non-indigenous crayfish species (NICS) associated with A. astaci and impacts survival of European indigenous crayfish species such as A. astacus severely. To conserve A. astacus, reintroduction of crayfish populations with genetics similar to the original ones into water bodies without the presence ofNICS is recommended. Lack ofpopulations to reintroduce might increase introductions of NICS. However, heated water from the production of renewable energy in P2X systems is an opportunity to create biosecure areas preserving crayfish and producing crayfish suitable for reintroduction. P2X means that surplus from renewable energy production is converted to something else (X). We found a need for further research on how industrial symbiosis and regulations on environmental hazardous activity can be used to improve the situation for A. astacus, on how to connect an industrywith surplus ofheat and oxygen in a biosecure way to a crayfish farm, and how to maintain a crayfish farm for reintroduction purposes for a very long time. Copyright (c) 2025 by The Author(s). Published by the International Association ofAstacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
We report the first confirmed occurrence of Cambaroides wladiwostokiensis Birstein & Vinogradov, 1934 in China, based on field surveys conducted between 2015 and 2024 in the Upper Morin and Suifun River basins. A total of 78 individuals were collected, and 62 adult specimens were examined in detail. This study presents the first comprehensive morphological description of the species from China, supplementing previous accounts that lacked dissection-based analyses. Diagnostic traits distinguishing C. wladiwostokiensis from sympatric congeners (C. dauricus, C. schrenckii) are clarified. Historical records were critically reassessed, and several misidentifications and ambiguous locality data were corrected. Additionally, our surveys documented local extirpations of C. dauricus and C. similis in parts of northeastern China. Major threats to native populations include habitat degradation, water pollution, and unregulated exploitation. Although C. wladiwostokiensis persists in some protected areas, its longterm survival is threatened by invasive species. This study highlights the urgent need for conservation measures targeting native East Asian crayfish and provides essential morphological and ecological data to support future monitoring and management strategies. Copyright (c) 2025 by The Author(s). Published by the International Association ofAstacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
A new species of freshwater crayfish, Euastacus coughrani sp. nov., is described from the Bemm, Brodribb and Queensborough River catchments in eastern Victoria, Australia. Euastacus coughrani sp. nov. inhabits perennial, small to medium, cool-flowing streams through a range offorest ecosystems including ancient wet eucalypt forests, cool and warm temperate rainforests at elevations between 251 m and 1050 m. The species' restricted extent of occurrence (422 km2) supports a conservation status of Endangered. Morphologically, E. coughrani sp. nov. is closely related to E. diversus and E. bidawalus and represents a genetically distinct population distributed between the two. This new species can be distinguished from its congeners by the morphology of the thorax, abdomen, chelae and gastric mill. Detailed insights into the species' ecology, biology, and conservation status are provided herein to facilitate and guide future conservation and management endeavors.
The stygobitic Caney Mountain cave crayfish, Orconectes stygocaneyi, is among the rarest crayfish species in North America. It is known only from Mud Cave, a small linear cave on the 3,200 ha Caney Mountain Conservation Area in Ozark County, Missouri. The species is listed as "Endangered" by the state of Missouri and "Threatened" by the American Fisheries Society. Previous studies documented its population range and limited life history notes; but little is known about Mud Cave's habitat We conducted a one-year study to document the caves water-chemistry, quality, and interior wetted pool volume, and how this habitat varies monthly, to establish a baseline for future study.
While previous studies have explored the impact of behavior and life history on environmental DNA (eDNA), little research has been conducted on the impact of molting on eDNA detectability and particle size for aquatic arthropods like crayfish. To address this knowledge gap, we conducted a study examining how molting affects eDNA detectability over a range ofparticle sizes using marbled crayfish ( Procambarus virginalis Lyko, 2017). We collected water samples from aquariums at pre- and post-molt time intervals and filtered our samples using sequential filtration from large to small filter pore sizes. We found that molting had a weak negative effect on eDNA detectability, and P. virginalis eDNA was most detectable throughout the study at our largest filter pore size (5.0 um) regardless of molt status. Additionally, time spent in aquariums had a strong, positive effect on eDNA detectability for P. virginalis. Given that molting had a weak effect on eDNA detectability for our study crayfish, we suggest that researchers align their sampling efforts with other seasonal life history events, like reproduction or egg extrusion, that have been demonstrated to improve eDNA detectability.
A survey was conducted on recently collected specimens of the rare eastern European astacid crayfish, Astacus colchicus. The study included a detailed examination and illustration of external morphology, mandible, gastric mill, and gills. Comparative analysis was carried out by comparing the morphology with other European members of the same family, Astacidae, namely Astacus astacus, Austropotamobius fulcisianus, Austropotamobius torrentium, and Pontastacus leptodactylus. The diagnosis of the genus Astacuswas updated, and a taxonomic key of European Astacidae is provided and illustrated. This comprehensive study enhances our understanding of the morphology and taxonomy of Astacidae, particularly shedding light on the distinctive features of Astacus colchicus in comparison to other closely related species
Freshwater Astacidea evolved from marine Astacidea, giving rise to four families with remarkable diversity. The Red Swamp Crayfish, Procambarus clarkii (Astacoidea: Cambaridae), is the most economically utilized and invasive species. The morphology of the postembryonic development of this species is described and illustrated for comparison with other Astacidea members. The evolutionary history of the rudimentary vestigial line and filaments on the epipodal plate was examined. Abbreviation of postembryonic stages and the development of telson segmentation of members of the freshwater Astacidea were compared with marine Astacidea. The abbreviation of the larval stage may be related to the phylogenetic relationships among Astacidea members in marine and freshwater environments. The body size of each postembryonic stage was compared among species from each of the four families. Larger-sized Astacidae and Cambaroididae become independent at Stage II, while smaller-sized Cambaridae and Parastacidae leave maternal care at Stage III. The smallest juveniles belong to Cambaridae in North and Middle America, contributing to the highest species diversity among the four families. Smaller size led to a larger number of juveniles and an extended maternal care period that was related to the higher survival of juveniles. It is proposed that the higher fertility contributed to the evolutionary success of the Cambaridae.
The Big Water Crayfish, Cambarus robustus, is native to several eastern U.S. states and Ontario, Canada. Cambarus robustus possesses several traits that make it a potential surrogate for federally listed species, such as the Big Sandy Crayfish, Cambarus callainus, and the Guyandotte River Crayfish, Cambarus veteranus. Basic husbandry information, like optimal temperature, and shelter requirements, have yet to be investigated for most Cambarus species. Therefore, to create a protocol for shelter requirements and preferences for federally listed Cambarus species, we conducted a shelter preference study with C. robustus. Thirty-one crayfish were placed in two treatments where opportunities to burrow underneath natural shelters, clear acrylic shelters, or tinted acrylic shelters were presented. Clear and tinted acrylic shelters are beneficial for investigators as they allow for monitoring of behavior and health without disrupting the crayfish. Each of the two trials lasted 24 hours and were video recorded to monitor behavior and shelter use. Our results suggest that C. robustus will use all shelter types, although natural shelters were occupied more frequently than acrylic shelters. Sex and size had minimal or no influence on shelter use. Future studies should continue to investigate husbandry and rearing techniques for Cambarus spp. and other species where propagation and head-starting efforts will commence.
Pacifastacus leniusculus (Dana 1852), the signal crayfish, is a freshwater astacid native to the Pacific Northwest and introduced in western Europe and Japan. Though P. leniusculus populations have been well-studied abroad, where they degrade local habitat and biodiversity, their ecology and natural history are less understood within their native range, where they fill key roles and risk out-competition by exotic crayfish. The present study describes density, morphology, and behavior of resident crayfish in a fourth- order Oregon stream, Tryon Creek, via surveys of nine sites from June-September 2022. Across sites, there was an estimated average P. leniusculus population density of 0.08 m-2, and no exotic crayfish were detected. Amongst crayfish collected (n = 162), total body length (TL) ranged from 13-90 mm, mu = 53 mm. Branchiobdellidans colonized one in four crayfish throughout Tryon Creek, damage to appendages occurred at a rate of 0.45, and the likelihood of both increased with TL. In a case study of Tryon's Hwy- 43 Culvert, crayfish showed potential signs of stress; across numerous sites, young juveniles resided gregariously. Despite the present study's novel strides toward native-range P. leniusculus population characterization, further research is encouraged to establish a well-rounded regional baseline.
Many freshwater ecosystems are at risk due to the detrimental impacts of increasing salinity. This is particularly true for coastal freshwater wetlands where increasing tropical cyclone intensity and sea level rise are threatening these habitats. Little is known, however, about salinity tolerances of many coastal freshwater species. The hammock crayfish, Procambarus lunzi (Hobbs), for example, inhabits coastal hammock islands and maritime forested wetlands in South Carolina, USA. Procambarus lunzi and other native crayfish are also at risk due to invasion by the red swamp crayfish, Procambarus clarkii (Girard), a species with a high salinity tolerance. The objective of this study was to document P. lunzi's response to chronic salinization under field conditions and to test acute salinity tolerances of two native and one invasive crayfish species under experimental conditions. Under field conditions, monthly sampling of a mesohaline wetland (range: 0.5-6.1 psu) revealed the presence ofP. lunzi throughout the year. Seven-day experimental trials on acute tolerance revealed high survival probabilities (>50%) of all three species at 30 psu. These results showhigh acute salinity tolerance for multiple crayfish species, but some indications that chronic salinization may be detrimental, demonstrating that salinization and non-native species may threaten coastal biodiversity. Copyright (c) 2024 by The Author(s). Published by the International Association of Astacology This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
For the stone crayfish, a threatened species listed in the Habitats Directive in Annex II and V, three monitoring methods were evaluated: hand capture by day, hand capture by night and eDNA sampling respectively. The lack of a standardized sampling method in Austria and the simultaneous obligation to monitor and report on the status of protected species requires therefore an evaluation of the different techniques. However, data show that day sampling massively favored the observation of juveniles whereas night sampling obtained higher shares of adults and males. Moreover, organic layer primarily determines the applicability of hand capturing methods. If the share of organic layer exceeded 42%, night sampling was more effective. In brooks with low amount of organic layer, no notable divergences were found. eDNA sampling provided reliable presence-absence data but cannot fully replace hand capturing methods. Data indicate that eDNA detectability depends probably on the discharge level. Below 1.5 L center dot s(-1) eDNA detection failed but provided reliable results in sections with a higher discharge regime. In summary, all three methods are appropriate for crayfish surveillance programs, but must be applied according to the sampling design appropriate for the research questions and with an awareness of their strengths and weaknesses. Copyright (c) 2023 by The Author(s). Published by the International Association of Astacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The Far North region of Ontario, Canada, is a wilderness area comprising 451,808 square kilometers of intact boreal forest and wetlands. Until the work presented here the most recent extensive survey for crayfish in the Far North region of Ontario was conducted in 1963. We sampled 81 locations across the Far North region of northern Ontario and the Hudson Bay Lowlands, Canada from 2009 to 2014 catching 96 specimens from 2 species: Faxonius virilis (Hagen) (92) and Faxonius propinquus (Girard) (4) These records define the northern boundary of freshwater crayfish. Unlike much of North America, species records were consistent with surveys conducted over 55 years ago. The Far North region of Ontario is facing proposed development at a scale not seen before, and our records provide necessary baseline data for ecosystem and wildlife monitoring, understanding potential future impacts, and to support sustainable resource management. Copyright (c) 2023 by The Author(s). Published by the International Association of Astacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Comprehensive surveys are critical to conserve and monitor crayfish species and communities, and detect crayfish invasions. The Missouri portion of the North Fork White River drainage (MONFWR) was never comprehensively surveyed, but adjacent drainage surveys suggested it could harbor species of conservation concern (SOCC). We surveyed the MONFWR to determine crayfish species richness, distributions of potential SOCC, and potential invasive species. We included recent sampling of the Arkansas portion of the drainage for a more holistic assessment of the entire drainage. We examined potential changes in crayfish communities after three decades at 22 previously sampled MONFWR locations. We also collected the first habitat association data for the endemic, Faxonius longidigitus. We detected eight taxa; none that were not known from the drainage. Faxonius neglectus chaenodactylus and Cambarus hubbsi were SOCC; F. n. chaenodactylus was common and abundant in the MONFWR; C. hubbsi was detected at only one site in Arkansas. Faxonius neglectus neglectus and Faxonius virilis were each detected only once and are likely introduced. Intermittent streams harbored diversity and abundance rivaling perennial segments. We observed no notable temporal differences between 22 historical and current samples. Faxonius longidigitus, detected at few sites in low numbers, was associated with deeper waters and larger substrates. Copyright (c) 2023 by The Author(s). Published by the International Association of Astacology. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
