Buřič and colleagues 2025

Buřič M, Ložek F, Görner T, Čuprová V, Kožený P, Mojžišová M, Vlach P, Štruncová E, Petrusek A, Kouba A, Svobodová J. 2025. Difficult to deal with: attempts for eradication of marbled crayfish from a small urban pond. Management of Biological Invasions 16(2): 443–464. https://doi.org/10.3391/mbi.2025.16.2.08

Abstract

The marbled crayfish is an emerging invasive species, mainly due to parthenogenetic reproduction and high adaptability. Its successful eradication seems to be possible only in early detected populations and under favourable conditions. The population of marbled crayfish was discovered in a small urban pond in Prague, Czech Republic, in August 2020. Shortly afterwards, management was initiated with the aim of complete eradication. The pond was harvested and drained twice in November 2020 and October 2021. The crayfish were collected, the exposed pond bottom was treated by liming and left dry over winter. Predatory fish were stocked in the pond after refilling. Survival of the crayfish after the pond draining in 2021 was likely facilitated by up to 40 cm deep burrows found under large boulders. No specimens were observed in the nearby stream and marbled crayfish presence was not detected by environmental DNA screening in the stream and three other standing waters in the vicinity. The combined efforts resulted in a reduction in crayfish densities by an order of magnitude between successive harvests, but complete eradication of marbled crayfish was not achieved by 2023, as individual juveniles were captured during monitoring in the following two years. The perch-dominated fish stock apparently exerts a strong predation pressure that may control the crayfish population, as no marbled crayfish were captured during monitoring in 2024. The current status of the population is unclear, and further monitoring is warranted. Effective cooperation between different institutions and stakeholders has been successfully established, and the public and stakeholders have been educated about the risks of invasive species. However, with prolonged activities aiming to eradicate the crayfish, we also experienced decrease of public support for further radical actions. This experience provides a solid basis for future invasive crayfish management activities at sites with similar conditions.

 

Keywords: invasive species • management • biological invasions • freshwater • crustacean • macroinvertebrates 

 

Coutinho Carneiro and colleagues 2025

Coutinho Carneiro V, Schäfer I, Diaz-Larrosa JJ, Böhl E, Hahn T, Hempelmann J, Venkatesh G, Nagarajan S, Roy S, Ng YL, Böhl F, Zibek S, Lyko F. 2025. Establishment and characterization of biofloc culture for marbled crayfish. Frontiers in Aquaculture 4. https://doi.org/10.3389/faquc.2025.1580560

Abstract

Biofloc technology is an innovative aquaculture approach that enhances water quality and reduces waste through the development of beneficial microbial communities. Marbled crayfish (Procambarus virginalis) are a newly discovered freshwater crayfish species that are distinguished by asexual reproduction, a genetically homogeneous all-female population structure and considerable robustness. These traits are attractive features for closed-system aquaculture production, which also mitigates the invasive risk associated with the species. Here we describe the establishment and characterization of biofloc culture for marbled crayfish. Juvenile crayfish raised in biofloc systems displayed robust growth with a six-fold weight increase over three months, comparable with other crustaceans under similar conditions. Metagenomic analysis revealed that biofloc communities consisted mostly of beneficial Gammaproteobacteria and Bacillariophyceae, with variations by environmental factors, such as temperature and light exposure. DNA methylation profiling identified systematic changes in response to biofloc environments, highlighting the potential of DNA methylation analysis for environmental biomarker identification. Finally, nutritional analysis showed that biofloc-grown crayfish produced meat with a highly favorable protein-to-fat ratio, while their shells retained considerable amounts of chitin, an important raw material for bioplastics production. Taken together, our study is the first to establish marbled crayfish biofloc culture and to characterize the interaction between the animals and the production system.

Keywords: biofloc technology • sustainability • aquaculture • marbled crayfish • epigenetics •
chitin

 

Aluma and colleagues 2025

Aluma MO, Kaldre K, Strand DA, Hurt M, Pukk L. 2025. eDNA-based detection of invasive crayfish and crayfish plague in Estonia. Environmental DNA 7(3): e70107. https://doi.org/10.1002/edn3.70107

 

Abstract

 

In Estonia, three invasive North American crayfish species—Pacifastacus leniusculus, Faxonius limosus, and Procambarus virginalis—have been detected through the annual monitoring program. To protect Astacus astacus, the only native freshwater crayfish species in Estonia, rapid and effective conservation-based management actions are necessary. Recently, the environmental DNA (eDNA) approach has been increasingly used in Europe to detect crayfish species and the crayfish plague pathogen Aphanomyces astaci. Our study explored the potential of integrating the eDNA approach into ongoing annual monitoring programs for invasive crayfish species and A. astaci. We also evaluated the relationship between eDNA concentration and signal crayfish population density at a single location. We filtered 139 eDNA samples from 16 water bodies and screened them for A. astacus, P. leniusculus, and A. astaci using singleplex qPCR assays. A subset of the samples was also screened for P. virginalis and F. limosus. Crayfish eDNA was detected in nine out of 14 water bodies where presence was confirmed by trapping, resulting in a 64% detection efficiency. Detection of P. virginalis was only observed in samples with amplifications below the limit of detection, and A. astaci eDNA was found in only one water body hosting invasive crayfish species. Although we could not establish a convincing quantitative correlation between the estimated P. leniusculus eDNA concentration and crayfish population density, we conclude that the eDNA approach is promising and, with further optimization, it can be integrated into routine monitoring of crayfish and crayfish plague pathogen as a supplement to traditional trapping methods.

 

Keywords: None provided. 

Short course on Marmorkrebs

The Invasive Species Center is offering a short course on Marmorkrebs.

The course description:

This short course will provide an overview on crayfishes, with a particular focus on marbled crayfish biology, spread, and impacts.

Lesson 1: Introduction to Aquatic Invasive Species

Lesson 2: Introduction to Crayfishes

Lesson 3: Marbled Crayfish Biology

Lesson 4: Marbled Crayfish Impacts

Lesson 5: Preventing the Spread of Invasive Crayfishes

This course takes about 2 hours. Score an 80% on the final exam, and score a certificate of completion! 

The Center’s Instagram page has a discount code that lets you take the course for free until the end of May! If you happen to be reading this in June 2025 or later, sorry that it is no longer free, but should still be affordable.

External links

Invasive Species Training

Invasive Species Center on Instagram (contains discount code) 

Sheppard and Ricciardi 2025

Sheppard NLM, Ricciardi A. 2025. Influence of warming on the functional responses of invasive omnivores, Procambarus crayfishes. Canadian Journal of Fisheries and Aquatic Sciences 82: 1-8. https://doi.org/10.1139/cjfas-2024-0334

Abstract

The red swamp crayfish (Procambarus clarkii) and the marbled crayfish (Procambarus virginalis) are congeneric invasive species whose potential impacts in the Great Lakes basin have generated concern. In laboratory experiments, we tested the functional responses of these omnivores to two common food resources, insect larvae (Chironomus bloodworms) and aquatic macrophytes (Eurasian milfoil Myriophyllum spicatum), to gain predictive information on their per capita effects under present (18°C) and projected future (26°C) climate scenarios for the basin. The maximum feeding rate of P. virginalis was higher at 18°C than at 26°C when presented with bloodworms but did not differ between temperatures when presented with macrophytes. By contrast, the feeding rate of P. clarkii did not change with temperature for either food resource. Due to their larger mean size, P. clarkii exhibited higher rates of resource (bloodworm and macrophyte) consumption than P. virginalis at both temperatures. These results suggest that trophic impacts of P. virginalis will dampen with increased warming, whereas P. clarkii will sustain larger impacts irrespective of temperature within the range tested.

 

Keywords: None provided.

Talking Marmorkrebs to the streets

 

 

Pleased to hear that Marmorkrebs were part of a show promoting outdoor activities,

 

Brianna Naklicki from the Ontario Federation of Anglers and Hunters was handing out information booklets to visitors passing by. She works for the organization’s invasive species awareness program.

On a table in front of her are jars containing examples of species of concern in the province, including zebra mussels and marbled crayfish.

Her job at the show was to spread awareness about invasive species around lakes and forests to all who will listen.

 

Ontario is, so far, the only place in North America where Marmorkrebs have been found in the wild, and is the largest jurisdiction to ban Marmorkrebs.

External links

Outdoor show hooks nature lovers into shopping local

Update on Marmorkrebs in Warsaw, Poland

A couple of recent news articles are reporting on the presence of Marmorkrebs in Warsaw. This location was already in my map of Marmorkrebs introductions. A bioblitz located seven individuals in Morskie Oko Park back in 2019.

Fast forward six years to 2025, and the population is estimated at 100,000 crayfish.

 

The article notes that there are removal efforts, but they can’t drain the pond, so culling them requires catching them by hand or trap. And in typical local media style, they stress the expense.

 

I do appreciate the safety warning:

 

 The expert emphasized that rakes do not attack a person if they are not provoked to do so. 

I don’t know of any crayfish that voluntarily attacks people with anything more than a pinch.

External links

Wpuścił raka do stawu w Warszawie. "Doprowadził do niepowstrzymanej ekspansji" (He released a crayfish into a pond in Warsaw. “He led to unstoppable expansion”)

 

Warszawa zmaga się z inwazją raka marmurkowego. Ekspert ostrzega (Warsaw is struggling with marbled crayfish invasion, expert warns)

 

Photo by Adrian Grycuk - Own work, CC BY-SA 3.0 pl, https://commons.wikimedia.org/w/index.php?curid=101324805

Everyday sexism

Always nice to stumble across a video mentioning marbled crayfish. I’m kind of used to them showing some other random crayfish species, but this one has a new thing that made me pause.

This video is titled, “This guy copies himself 2,000 times!”

Since marbled crayfish are all female, a better title would be, “This gal copies herself 2,000 times.”

Eiler and colleagues 2025

Eiler A, Stensrud E, Osman O. 2025. Detection of marbled crayfish Procambarus fallax. protocols.io. https://dx.doi.org/10.17504/protocols.io.q26g78199lwz/v1

 

Abstract

Taqman QPCR assay for marbled crayfish Procambarus fallax.

 

Keywords:  None provided.

 

The Crayfish Almanac

Don’t know how I missed this last year, but Michigan State University released Great Lakes Almanac to Invasive Crayfish.

It has one of the best short identification guides for Marmorkrebs I’ve seen. Click to enlarge!

Marbled crayfish (or marmokrebs) originated in the aquarium trade and are often called the self-cloning crayfish. All marbled crayfish are female and the offspring are clones. This species is of high concern because a single individual can produce an entire population in a short time.

This species has a distinct marbling pattern, but other species may look similar. Male crayfish with this pattern are not marbled crayfish.

To determine if its a female, look for a round pocket-like feature located on the underside between the last pair of walking legs. This is the sperm pouch (called an ‘annulus ventralis’) .

External links

Great Lakes Almanac to Invasive Crayfish 

Golubev and colleagues 2024b

Golubev AP, Ulashchyk EA, Bodilovskaya OA. 2024. Modeling the growth of the invasive river crayfish species Procambarus virginalis (Decapoda, Astacidea) under different temperature conditions. https://www.researchgate.net/publication/387918897_Modeling_the_growth_of_the_invasive_river_crayfish_species_Procambarus_virginalis_Decapoda_Astacidea_under_different_temperature_conditions

Abstract

In the marbled crayfish Procambarus virginalis, the dependence of the duration of inter-larval intervals on body weight and the magnitude of body weight gains for individual inter-larval intervals in the temperature ranges 15.3–17.9 °С, 7.5–18.9, 19.1–20.8, 21.0–22.8, 22.9–25.2 and 25.3–28.9 °С was determined. The growth curves of individuals in these temperature ranges and the sum of effective temperatures (Sef) of individuals during juvenile growth and breeding periods were calculated from these data. The average Sef value for the juvenile period of P. virginalis (until newborn individuals reach a body weight of 1.4 g) in the studied temperature ranges is 4316 degree·days at the biological zero temperature of 7.6 °C. For the breeding period (until reaching the body weight from 1.4 g to the limit weight of 15 g) – respectively 10630 degree·days and 3.0 °C. Based on the annual dynamics of mean monthly temperatures in six continental water bodies within the invasive range of P. virginalis (Sweden, Belarus, Germany, Slovakia, North Macedonia and Malawi), Sef values were calculated for the periods of the year during which juvenile growth and reproduction of sexually mature individuals are possible. In temperate water bodies located in Sweden, Belarus, Germany and Slovakia, Sef values during the juvenile growth period vary between 1083 and 2099 degree·days. In the more southern body of water in Northern Macedonia, this value reaches 2990 degree·days, and in the tropical African body of water in Malawi it reaches 7076 degree·days. Consequently, newborn individuals of P. virginalis, which in water bodies of the temperate zone of Europe hatch in the first half of summer, can reach sexual maturity only in the third summer of life, and in a tropical water body – already in the first summer of life. Sef values for periods of the year favorable for the growth of sexually mature individuals in the studied water bodies of Europe increase from 2031 degree·days (water body in Sweden) to 4657 degree·days (water body in Northern Macedonia). In the tropical water body of Malawi, this figure reaches 8058 degree·days, i.e. the maximum life span of P. virginalis in this water body does not exceed two years. Nevertheless, throughout the entire range, sexually mature individuals of P. virginalis are capable of producing no more than 2–5 clutches of eggs per life cycle.

Note: The ResearchGate page includes a link to the DOI 10.46646/2521-683X/2024-4-18-34. At the time of this writing in January 2025, this link is not working. I will update this entry with more information if I learn more.

Golubev and colleagues 2024a

Golubev AP, Ulashchyk EA, Bodilovskaya OA, Giginjak YG. 2024. Assessing the invasive potential of parthenogenetic marbled crayfish Procambarus virginalis Lyko, 2017 (Decapoda, Astacidea) in the water bodies of the temperate zone of Europe. Doklady Natsional’noi akademii nauk Belarusi = Doklady of the National Academy of Sciences of Belarus 68(2): 129–137. (In Russian). https://doi.org/10.29235/1561-8323-2024-68-2-129-137

 Abstract

The experiment examined the effect of temperature on the parameters of reproduction and growth in female marbled crayfish. At temperatures close to 20 °C, females began to reproduce at 10–11 months with a body weight of 0.84–1.20 g, but up to 80 % of their egg clutches were nonviable. The duration of egg embryogenesis with an increase in temperature from 16–17 to 26–27 °C decreased from 66–69 days to 21–24 days with a lower temperature development threshold equal to 13.1 °C. A similar molting value that determined the growth rate of individuals in juveniles weighing up to 0.34 g was 13–14 °C, but in sexually mature females it decreased to 5 °C. In water bodies of the temperate zone with a short growing season, females were able to reach sexual maturity only in the third summer of life and produced no more than two clutches of eggs during their life cycle. Hence, the invasive potential of marbled crayfish in the temperate zone of Europe is very limited.

Аннотация

В эксперименте исследовано воздействие температуры на параметры размножения и роста у самок мраморного рака. При температурах, близких к 20 °С, самки начинали размножаться в возрасте 10–11 месяцев при массе тела 0,84–1,20 г, однако до 80 % их кладок яиц были нежизнеспособными. Длительность эмбриогенеза яиц при повышении температуры от 16–17 до 26–27 °С снижалась от 66–69 до 21–24 суток при нижнем температурном пороге развития, равном 13,1 °С. Аналогичный показатель для частоты линек, которая определяет скорость роста особей, у молоди массой до 0,34 г составлял 13–14 °С, но у половозрелых самок он снижается до 5 °С. В водоемах умеренной зоны с коротким сезоном вегетации самки способны достичь половой зрелости лишь на третье лето жизни и произвести за жизненный цикл не более двух кладок яиц. Отсюда инвазивный потенциал мраморного рака в умеренной зоне Европы весьма ограничен.

Garcia and colleagues, 2024

García SM, Curtis AN, Hartman JH, Reinhofer JP, Sawyer EK, Larson ER. 2024. Does crayfish molting affect environmental DNA detectability? Freshwater Crayfish 29(1): 37-47. https://doi.org/10.5869/fc.2024.v29-1.37

Abstract

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 of particle 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 µm) 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.

 

Keywords: None provided.