Friday, April 04, 2025

 SPACE / COSMOS

 

Technologies to mitigate space debris and improve in-orbit satellite services



Innovation by PERSEI Space, a UC3M spin-off company.




Universidad Carlos III de Madrid

Technologies to mitigate space debris and improve in-orbit satellite services 

image: 

PERSEI Space.

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Credit: UC3M




Sustainability in space and the fight against the accumulation of waste produced in Earth orbit are the objectives pursued by PERSEI Space, a company whose partners include two researchers from Universidad Carlos III de Madrid (UC3M) and which has developed a space electrodynamic tether technology that is useful in this area. 

This spin-off, which has been incubated by the European Space Agency (ESA) and is being supported by the Center for Innovation in Entrepreneurship and Artificial Intelligence (C3N-IA) of the UC3M - Leganés Tecnológico Science Park, has the support of the European Innovation Council through the E.T.PACK-F and E.T.COMPACT projects.

“Our company was created to address two of the biggest challenges facing the space sector today: space debris removal and in-orbit services. The latter allow us to extend the useful life of satellites and carry out key activities such as refueling, repair and towing of satellites from their initial orbit to their final destination,” explains Jesús Manuel Muñoz Tejeda, CEO and co-founder of PERSEI Space. 

Space debris poses a very serious threat to the sustainability of space operations since, due to the high speed at which debris moves in Earth orbit, an impact can result in severe damage and the generation of more small debris. In addition, the current density of space debris is already above the threshold that triggers an uncontrolled chain of collisions, known as the Kessler syndrome.  

To get rid of this space junk, PERSEI Space is working on space tethers, a technology with three key features. “The first is that it does not need fuel, unlike other de-orbiting systems. The second is that our technology is reversible; it can serve to both increase and decrease the orbital height . And the third feature is that it is scalable, since it serves a wide range of satellite masses. With all this, we can develop autonomous de-orbiting systems, a unique feature of our technology that ensures that the satellite does not leave space debris, even if it ceases to be operational,” explains Jesús Manuel Muñoz Tejeda.

Space tethers 

The system is based on electrodynamic tethers, aluminum ribbons, generally hundreds of meters long and a few centimeters wide, which work by interacting with the ionospheric plasma and the Earth's magnetic field to generate a force known as the Lorentz force. 

“The interaction of the electric current in the tether with the Earth's magnetic field generates a drag force capable of lowering the satellite's altitude, facilitating its de-orbiting without requiring fuel, which translates into significant savings in mass and volume,” says Gonzalo Sánchez Arriaga, professor in the UC3M Department of Aerospace Engineering and co-founder of PERSEI Space.

PERSEI Space is leading a first demonstration mission for 2026, thanks to a launch opportunity facilitated by ESA's Flight Tickets Initiative and the European Commission. The deorbiting equipment for this demonstration has a mass of 20 kg, and includes a space tether approximately 430 meters long that, once in orbit, will deploy and interact with the ambient plasma and magnetic field, generating a drag force that will deorbit the satellite within a few months. This equipment has been funded with 2.5 M€ by the European Innovation Council, and in collaboration with SENER Aerospace, the University of Padua and the Technical University of Dresden. The development of the technology could not be more timely, as new European and US guidelines have reduced the maximum time satellites can remain in orbit after the end of their mission from 25 to 5 years.

The company PERSEI Space has signed ESA's Zero Space Debris Charter initiative, which seeks to achieve a sustainable space by 2030. The company, in turn, is linked to the UC3M's Business Creation and Entrepreneurial Development program and also has the support of the Madrid City Council.

More information: https://www.uc3m.es/ss/Satellite/InnovacionEmprendimiento/es/TextoMixta/1371408324113/

Video: https://youtu.be/201NR61lm0s

China’s Chang’e-6 returned lunar samples reveal differences in space environment in the Moon’s near and far side




Science China Press
Secondary electron (SE) images of the 7 mineral clasts from Chang’e-6 lunar farside sample investigated in this study. 

image: 

Yellow rectangles indicate the positions where FIB sampling was carried out and the curved yellow lines indicate mineral boundaries. Pgt, pigeonite; Tro, troilite; Ilm, ilmenite; Aug, augite; Chr, chromite; An anorthite; Fo, forsterite.

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Credit: ©Science China Press





This study is led by Dr. XIAN Haiyang and Dr. ZHU Jianxi of the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. On June 25, 2024, the Chang’e-6 mission successfully achieved the world’s first sampling of the lunar farside and returned safely to Earth. In August, based on his outstanding performance in the Chang’e-5 sample research, Dr. Xian received the first batch of Chang’e-6 samples. This marks the first time in human history that samples have been directly obtained from the lunar farside, and the research team hopes to use these samples to gain insights into the space weathering characteristics on the lunar farside. The space weathering features recorded in lunar samples can sensitively capture information about the surrounding space environment, helping us better understand the conditions on the lunar farside.

Under Dr. Xian’s guidance, his student Lin Jiarui at the Electron Microscopy Center of the Guangzhou Institute of Geochemistry analyzed these precious samples one by one using a scanning electron microscope (SEM). To preserve as much of the surface information as possible, she chose to evenly distribute the fine-grained powder on conductive adhesive and then deposited a 10 nm carbon film, observing the samples at a low voltage of 3 kV. After examining nearly a thousand particles, she noted that the Chang’e-6 samples exhibited noticeably less melt drops and melt splashes on their surfaces. To further systematically study the space weathering characteristics, she selected seven mineral particles with distinct compositions using energy-dispersive spectroscopy (EDS), which together represent the main lunar mineral types.

In subsequent transmission electron microscopy (TEM) investigations, Lin and other team members prepared a feldspar particle (designated P2‑001) using focused ion beam (FIB) techniques and discovered that its surface lacked the nanophase metallic iron (npFe⁰) particles commonly found in Apollo samples. Typically, the surface of feldspar in Apollo samples exhibits a vapor‑deposited layer generated by micrometeorite impacts that contains npFe⁰. They further conducted EDS mapping on the other seven FIB sections under TEM, and the results showed no significant compositional differences between the edges and interiors of these minerals. All regions displaying observable space weathering features—including the amorphized layers, vesicles, and npFe⁰ grains—were consistent with the substrate mineral composition, indicating that these features can be attributed to the damage caused by solar wind radiation on the substrate minerals.

Lin further measured the thickness of the amorphized layers and the grain sizes of npFe⁰, and counted the solar wind tracks in pyroxene and olivine to estimate the solar wind exposure time of the particles. The study found that the solar wind exposure time of the Chang’e-6 samples was close to the minimum observed in the Apollo 11 samples, lower than that of the other Apollo samples, and slightly shorter than that of the Chang’e-5 samples. However, surprisingly, the npFe⁰ grain sizes in the Chang’e-6 samples were larger. “This might suggest that solar wind radiation in this region leads to more pronounced segregation and aggregation of iron,” she noted. These exciting new results add to the growing evidence that space weathering on the lunar farside may differ from that on the nearside, and, contrary to previous findings from Apollo and Chang’e-5 samples, solar wind radiation plays a more dominant role in the space weathering process on the lunar farside.

There are differences in the solar wind’s influence on different regions of the Moon. During each synodic month, the near side of the Moon enters Earth’s magnetotail, where the protection afforded by Earth’s magnetic field reduces its exposure to the solar wind; in contrast, the farside is continuously exposed to direct solar wind radiation. Moreover, due to orbital dynamics, different locations on the Moon experience varying impact velocities from cometary and asteroidal meteoroids. The relative velocity between the Moon’s surface and impacting meteoroids changes with the lunar phase: during a full moon, when the Moon and meteoroids move in the same orbital direction, the relative velocity increases; the opposite occurs during a new moon.

Micrometeoroid impacts and solar wind radiation are the two primary processes driving space weathering, but the effective sputtering rate from the solar wind and vapor deposit from micrometeorite impacts offset each other. Therefore, when discussing space weathering mechanisms, it is essential to consider the relative contributions of both factors under different space environments. The findings from the Chang’e-6 samples indicate that on the lunar farside, the effect of the solar wind exceeds that of micrometeorite impacts, further demonstrating that the space weathering process is regulated by variations in the space environment.

Since the first images of the lunar farside were captured in 1959, it has been evident that its topography is markedly different from that of the nearside—a phenomenon known as the Moon’s “dichotomy.” However, whether the lunar space environment also exhibits a similar “dichotomy” had until now only been inferred from remote sensing spectra. The latest analysis of the Chang’e-6 samples provides direct, sample‑based evidence for this hypothesis, highlighting the critical role of space environmental variables in the space weathering process. This discovery not only deepens our understanding of how solar wind radiation and micrometeorite impacts shape the lunar surface, but also offers important insights for studying the space weathering evolution of other airless bodies.

(a) The relative influence of solar wind on different lunar locations. (b) The relative (micro)meteoroid flux at different longitudes. (c) The relative contribution of solar wind and (micro)meteoroid impact at different lunar sampling sites.

Credit

©Science China Press

See the article:

Differences in space weathering between the near and far side of the Moon: Evidence from Chang’e-6 samples

https://doi.org/10.1093/nsr/nwaf087

Warwick astronomers discover doomed pair of spiralling stars on our cosmic doorstep



Warwick astronomers discover the first double white dwarf binary, destined to explode as type 1a supernova




University of Warwick

A digital illustration of the immense explosion of this double white dwarf binary star system, named WDJ181058.67+311940.94 

image: 

In this picture, we capture the binary in the moment where the first white dwarf has just exploded, hurtling material towards its nearby companion which is on the cusp of explosion too. This event will occur in about 23 billion years, yet in only 4 seconds do both stars explode (Credit: University of Warwick/Mark Garlick) 

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Credit: Credit University of Warwick/Mark Garlick




University of Warwick astronomers have discovered an extremely rare, high mass, compact binary star system only ~150 light years away. These two stars are on a collision course to explode as a type 1a supernova, appearing 10 times brighter than the moon in the night sky.  

Type 1a supernovae are a special class of cosmic explosion, famously used as ‘standard candles’ to measure distances between Earth and their host galaxies. They occur when a white dwarf (the dense remnant core of a star) accumulates too much mass, is unable to withstand its own gravity, and explodes.  

It has long been theoretically predicted that two orbiting white dwarfs are the cause of most type 1a supernova explosions. When in a close orbit, the heavier white dwarf of the pair gradually accumulates material from its partner, which leads to that star (or both stars) exploding. 

This discovery, published today in Nature Astronomy, has not only found such a system for the first time, but has found a compact white dwarf pair right on our doorstep in the Milky Way.  

James Munday, PhD researcher at Warwick and leader of the investigation said, “For years a local and massive double white dwarf binary has been anticipated, so when I first spotted this system with a very high total mass on our Galactic doorstep, I was immediately excited.” 

“With an international team of astronomers, four based at The University of Warwick, we immediately chased this system on some of the biggest optical telescopes in the world to determine exactly how compact it is.”  

“Discovering that the two stars are separated by just 1/60th of the Earth-Sun distance, I quickly realised that we had discovered the first double white dwarf binary that will undoubtedly lead to a type 1a supernova on a timescale close to the age of the universe.”  

“At last, we as a community can now account for a few per cent of the rate of type 1a supernovae across the Milky Way with certainty.” 

Significantly, James’s new system is the heaviest of its type ever confirmed, with a combined mass of 1.56 times that of the Sun. At this high of a mass, this means that, no matter what, the stars are destined to explode.  

The explosion is not due for another 23 billion years, however, and despite being so close to our solar system, this supernova will not endanger our planet.  

Right now, the white dwarfs are leisurely spiralling around each other in an orbit taking longer than 14 hours. Over billions of years, gravitational wave radiation will cause the two stars to inspiral until, at the precipice of the supernova event, they will be moving so fast that they complete an orbit in a mere 30 – 40 seconds. 

Dr. Ingrid Pelisoli, Assistant Professor at The University of Warwick and third author, added: “This is very significant discovery. Finding such a system on our galactic doorstep is an indication that they must be relatively common, otherwise we would have needed to look much further away, searching a larger volume of our galaxy, to encounter them.  

“Finding this system is not the end of the story though, our survey searching for type 1a supernova progenitors is still ongoing and we expect more exciting discoveries in the future. Little by little we are getting closer to solving the mystery of the origin of type 1a explosions.” 

For the supernova event, mass will transfer from one dwarf to the other, resulting in in a rare and complex supernova explosion through a quadruple detonation. The surface of the mass-gaining dwarf detonates where it is accumulating material first, causing its core to explode second. This ejects material in all directions, colliding with the other white dwarf, causing the process to repeat for a third and fourth detonation.  

The explosions will completely destroy the entire system, with energy levels a thousand trillion trillion times that of the most powerful nuclear bomb.  

Billions of years into the future, this supernova will appear as a very intense point of light in the night sky. It will make some of the brightest objects look faint in comparison, appearing up to ten-times brighter than the moon and 200,000 times brighter than Jupiter. 

More details can be found in the full Nature Astronomy publication: DOI: 10.1038/s41550-025-02528-4 

ENDS 

Notes for Editors 

University of Warwick press office contact: 

Matt Higgs – Media & Communications Officer (Sciences) 

Matt.Higgs@warwick.ac.uk | +44 (0) 7880175403 

General and out of hours press office number +44 (0)7392 125605 (please call as emails are not checked out of office hours) 

Research Funding: 

James Munday was supported by funding from a Science and Technology Facilities Council (STFC) studentship. Ingrid Pelisoli acknowledges support from The Royal Society through a University Research Fellowship (URF/R1/231496) 

Image Credit: 

Artist’s impression available to download here. Images are free for use if used in direct connection with this story, but image copyright and credit must be ‘University of Warwick/Mark Garlick’ 

Caption:  A digital illustration of the immense explosion of this double white dwarf binary star system, named WDJ181058.67+311940.94. In this picture, we capture the binary in the moment where the first white dwarf has just exploded, hurtling material towards its nearby companion which is on the cusp of explosion too. This event will occur in about 23 billion years, yet in only 4 seconds do both stars explode (Credit: University of Warwick/Mark Garlick) 

Animation Credit:  

Animation of the supernova event available to download here. Animation is free to use but full credit must be attributed to ‘Dr. Ruediger Pakmor, Scientific Staff, Max Planck Institute for Astrophysics’ 

About Warwick’s Astronomy and Astrophysics Group: 

With over 100 staff and students, the Astronomy and Astrophysics group at Warwick is interested in a vast range of scales across the Universe: planetary systems, how they form, live and die; stars, stellar binaries and the exotic physical processes that they allow us to explore; as well as the transient events which mark the end of stellar lifetimes and the galaxies stars inhabit across the Universe. More details about The University of Warwick Astronomy & Astrophysics group can be found here: https://warwick.ac.uk/fac/sci/physics/research/astro/  


The type Ia supernova explosio [VIDEO] | 

This is a movie of the explosion of a double white dwarf binary star system. The simulation was published in Nature Astronomy by James Munday and collaborations in LINK. Full credit goes to Dr. Ruediger Pakmor (Max-Planck-Institut für Astrophysik) for conducting this simulation and authorising it to be shared. The double white dwarf has the highest total mass known to date, coming in at (1.555+-0.044) times the mass of the Sun. The more massive star that is gaining material has a mass of (0.834+-0.039) solar masses, and the less massive one (0.721+-0.020) solar masses.

Credit

Full credit goes to Dr. Ruediger Pakmor (Max-Planck-Institut für Astrophysik)

 

AMERIKA

Frequent exposure to gun violence is associated with depression, suicide and mental health



In Rutgers Health study, nearly 40% of participants surveyed reported hearing gunshots multiple times throughout their lives





Rutgers University




Exposure to gun violence can severely impact one’s mental health, often leading to depression, suicidal ideation and increased need for mental health support and resources, according to a Rutgers Health study.

A national survey of 8,009 non-institutionalized people older than 18 participated in an online-based panel that examined the relationship between gun violence exposure and mental health, including suicide. The study outlined both lifetime and past year exposure to gun violence and the association it has with increased depression and suicide risks.

“This is the first study using nationally representative data that demonstrates a link between exposure to gun violence and suicide,” said lead author Daniel Semenza, director of research at the New Jersey Gun Violence Research Center and assistant professor at the Department of Urban-Global Public Health at the Rutgers School of Public Health and in the Department of Sociology, Anthropology and Criminal Justice at Rutgers University. “When we think about what we can do to improve suicide prevention efforts, we have to include interpersonal violence prevention in the conversation.”

Nearly 40% of participants reported hearing gunshots multiple times throughout their lives. Overall, 12% of the participants said they experienced high exposure to gun violence, with five or more incidents throughout their lives, while about 27% said they had heard a gunshot within the past year alone.

More frequent and more recent gun violence exposure was generally associated with a heightened risk for depression, suicide and increased use of mental health services.

The recent study was published in the journal Social Science & Medicine.

Semenza and coauthors of the study found that gun violence exposure, even when indirect, has profound consequences on mental health. They said that addressing interpersonal violence is essential for any strategy aimed at reducing suicide rates. Their findings reveal that both single instances and repeated exposure to various forms of gun violence significantly harm mental well-being.

Participants reported repeated exposure to certain forms of gun violence, such as knowing someone who died by firearm suicide (8%), being threatened with a gun (5%), knowing a family member or friend who was shot (6%) and witnessing a shooting (3%).

“Gun violence exposure is harmful for many different health outcomes, but this study shows that both the frequency and the recency of exposure to gun violence is detrimental to mental well-being,” Semenza said.

 

US Border region emergency medical services in migrant emergency care




JAMA Network Open



About The Study:

 The findings of this qualitative study of emergency medical services (EMS) clinicians suggest that migration has a complex, multidimensional influence on EMS clinicians in the border region. Deterrence-focused actions have not decreased the number of crossings but rather pushed migrants to cross in more dangerous ways, leading to more injuries and deaths. The findings suggest that the strain placed on local EMS clinicians is unsustainable and may be exacerbated by increased deterrence-based policies. Instead, border-region EMS clinicians need increased federal funding to support their work.



Corresponding Author: To contact the corresponding author, Christine Crudo Blackburn, PhD, email ccblackburn@tamu.edu.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jamanetworkopen.2025.3111)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

#  #  #

Embed this link to provide your readers free access to the full-text article This link will be live at the embargo time https://jamanetwork.com/journals/jamanetworkopen/fullarticle/10.1001/jamanetworkopen.2025.3111?guestAccessKey=c0957767-f5eb-4d6d-88a4-15c747418b57&utm_source=for_the_media&utm_medium=referral&utm_campaign=ftm_links&utm_content=tfl&utm_term=040325

About JAMA Network Open: JAMA Network Open is an online-only open access general medical journal from the JAMA Network. On weekdays, the journal publishes peer-reviewed clinical research and commentary in more than 40 medical and health subject areas. Every article is free online from the day of publication. 

AMERIKA

Deporting immigrants may further shrink the health care workforce



JAMA



About The Study: 

More than 1 million noncitizen immigrants (one-third of them undocumented) work in health care in the U.S. Their ranks include skilled personnel who would be difficult to replace, especially if legal immigration is further restricted. Many health care workers may be removed if President Trump implements plans to deport undocumented immigrants and those losing temporary protected status (e.g., from Haiti and Venezuela).


Corresponding Author: To contact the corresponding author, Lenore S. Azaroff, MD, ScD, email Lenore_Azaroff@yahoo.com.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jama.2025.3544)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

#  #  #

Embed this link to provide your readers free access to the full-text article This link will be live at the embargo time https://jamanetwork.com/journals/jama/fullarticle/10.1001/jama.2025.3544?guestAccessKey=f5aafb3b-b3c9-4170-8e81-aa183ea6dfac&utm_source=for_the_media&utm_medium=referral&utm_campaign=ftm_links&utm_content=tfl&utm_term=040325

 

US Resident physician intentions regarding unionization




JAMA Network Open




About The Study:

 In this survey study, most resident physicians reported either being in a union or supporting unionization at their institution, citing pay and financial security as critical factors in their consideration of unionization. Future research should investigate other factors and whether unionization achieves its goals of increased pay and benefits, work hours, and well-being.


Corresponding Author: To contact the corresponding author, Laura K. Barger, PhD, email lkbarger@hms.harvard.edu.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jamanetworkopen.2025.3106)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

#  #  #

Embed this link to provide your readers free access to the full-text article This link will be live at the embargo time https://jamanetwork.com/journals/jamanetworkopen/fullarticle/10.1001/jamanetworkopen.2025.3106?guestAccessKey=c0957767-f5eb-4d6d-88a4-15c747418b57&utm_source=for_the_media&utm_medium=referral&utm_campaign=ftm_links&utm_content=tfl&utm_term=040325

About JAMA Network Open: JAMA Network Open is an online-only open access general medical journal from the JAMA Network. On weekdays, the journal publishes peer-reviewed clinical research and commentary in more than 40 medical and health subject areas. Every article is free online from the day of publication. 

 

Climate change and prehistoric human populations: Eastward shift of settlement areas at the end of the last ice age





University of Cologne
Population shifts in prehistoric Europe 

image: 

The map shows population shifts from the south-western to the north-eastern Europe during the last cold phase of the Ice Age.

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Credit: Isabell Schmidt, University of Cologne




A new study sheds light on how prehistoric hunter-gatherer populations in Europe coped with climate changes over 12,000 years ago. Led by scientists from the University of Cologne, a team of 25 prehistoric archaeologists from twenty European universities and research institutions revealed significant shifts in population size and density during key periods at the end of the last Ice Age, specifically during the Final Palaeolithic between 14,000 and 11,600 years ago. The study has been published in PLOS One under the title ‘Large scale and regional demographic responses to climatic changes in Europe during the Final Palaeolithic’.

The results reveal that the first establishment of a larger human population in north-eastern central Europe during the Final Palaeolithic was followed by a dramatic population decline during the last cold period (Greenland Stadial 1) of the Ice Age. This decline reduced the total population of Europe by half. However, the study found that some areas in central Europe show stability or even a slight increase in population size against the general trend. The team interprets this finding as evidence of human migration towards the east in response to worsening climate conditions.

By compiling a comprehensive database on archaeological sites from this period and using a cutting-edge geostatistical method called the Cologne Protocol, the researchers estimated population sizes and densities of prehistoric humans across different regions of Europe. The protocol provides a standardised procedure to estimate prehistoric demographic data, allowing for diachronic comparisons. The identified shifts in regional population sizes provide new insights into how early humans responded to the environmental challenges of their time.

The study focuses on two key periods: Greenland Interstadial 1d-a (GI-1d-a) and Greenland Stadial 1 (GS-1). During GI-1d-a, a warmer period of the Final Palaeolithic, humans continued to repopulate and expand into northern and north-eastern central Europe, making this region the centre of demographic dynamics in Europe for the first time in prehistory. Populations in south-western Europe, particularly in Spain and France, began to decline compared to population estimates for the preceding periods of the Upper Palaeolithic.

When the climate turned much colder during the subsequent GS-1, a climatic period known in the northern Hemisphere as the ‘Younger Dryas’, the total population of Europe decreases by half. But the new study shows that regional dynamics varied considerably: The estimates indicate an increase in population density in some areas of Europe (e.g. northern Italy, Poland and north-eastern Germany) as well as a general shift of populated areas from west to east. “These observations probably reflect the eastward movement of people in response to the very abrupt and pronounced climatic cooling during the Younger Dryas,” explains Dr Isabell Schmidt from the University of Cologne’s Department of Prehistoric Archaeology. “Humans during the Final Palaeolithic apparently responded by migrating to more favourable areas.”

The Cologne researchers are familiar with extreme population declines in Prehistory, such as during the late Gravettian (29,000 to 25,000 years ago), when cooler temperatures reduced populations in western and central Europe by up to two-thirds, leading to the extinction of regional populations.

Although demographic dynamics, particularly in these early phases of human prehistory, are still poorly understood, the new study adds to a growing body of evidence on how prehistoric humans responded to climate change, investigated at the University of Cologne in the framework of the Collaborative Research Centre 806 - Our Way to Europe, which was funded by the German Research Foundation (DFG) from 2009 to 2021. This work is currently being continued by the project HESCOR (Human and Earth System Coupling Research) at the University of Cologne, funded by the Ministry of Culture and Science of the State of North Rhine-Westphalia.

 

 

Researchers from MARE ULisboa discover that the European catfish, an invasive species in Portugal, has a prolonged breeding season, enhancing its invasive potential

Peer-Reviewed Publication

Faculty of Sciences of the University of Lisbon

Gonadosomatic-index (GSI) of female and male European catfish Silurus glanis specimens in relation to water temperature in the Lower River Tagus (LRT) 

image: 

Gonadosomatic-index (GSI) of female (dark colour) and male (white colour) European catfish Silurus glanis specimens in relation to water temperature (dashed line) in the Lower River Tagus (LRT). The box represents the interquartile range (IQR; 25th and 75th percentiles), and the line within the box is the median. Whiskers represent the 75th percentile + 1.5 × IQR and the 25th percentile + 1.5 × IQR. Water temperature values are shown as mean and extracted from the SNIRH database ( https://snirh.apambiente.pt/). Numbers in brackets denote the number of female and male individuals used in the analysis, separated by a slash.

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Credit: Gkenas, C., Sequeira, V., Ribeiro, D., Gago, J., Dias, D., Verma, C.R., Kumkar, P. and Ribeiro, F.,

The European Catfish is the largest freshwater fish in Europe, reaching up to 2.8 meters in length and 130 kg in weight. It was first detected in Portugal in 2014. As a top predator, it has no natural enemies and exhibits high fecundity, with females capable of producing up to half a million oocytes (unfertilized eggs). “This is not new information, as this invasive species reaches large sizes, and there is a direct relationship between abdominal cavity volume and the total number of oocytes produced,” said Christos Gkenas, a researcher at MARE-ULisboa and the study’s lead author. “What surprised us was that this fish has a prolonged breeding season, lasting almost five months, and that its oocytes are quite large, reaching over 3 mm in diameter.”

Over two years, from January 2022 to November 2023, nearly 700 catfish were captured using electrofishing and gill nets. The researchers found that the species spawns between February and June. This strategy allows its offspring to have different survival opportunities when facing extreme hydrological events (e.g., spring floods) and helps avoid competition for food resources among juveniles. The study also determined that European Catfish individuals reach sexual maturity at around 70 cm in length (approximately three years of age), which is considered early given that the species can live up to 70 years.

“Our work is crucial for controlling this species' population because our efforts should focus on removing larger individuals, which have higher fecundity,” said Filipe Ribeiro, the study's lead researcher, also from MARE-ULisboa. “The density of these animals is particularly high in protected areas, such as the International Tagus Natural Park. In October, as part of the LIFE-PREDATOR project, we removed approximately 1,200 kg of Catfish—about 100 individuals—in just three days from a small 10 km stretch of the Ponsul River.”

“The establishment of capture and removal teams to reduce Catfish populations is essential to mitigate the impact of this massive invader in Portugal,” Ribeiro concluded.

The LIFE-PREDATOR project titled “LIFE Predator – Preventing, Detecting, and Reducing the Spread of Silurus glanis in Southern European Aquatic Systems to Protect Aquatic Biodiversity”  is funded by the European Union’s LIFE Program, is coordinated by the National Research Center in Italy and involves 11 researchers from three countries and will continue until August 2027.

Logistic regression curve of the proportion of mature female (upper panel) and male (lower panel) European catfish Silurus glanis specimens with total length in the Lower River Tagus (LRT). The solid line represents the model-predicted values, the dashed lines represent the corresponding 95% confidence intervals, and the red lines indicate the respective values in the Figure.

Histological sections of reproductive active ovaries of European catfish Silurus glanis: a) ovary with CA and AVTG oocytes, b) ovary with several PG and AVTG oocytes, c) ovary with EVTG oocyte, d) oocyte with PG, CA and AVTG oocytes. AVTG – advanced vitellogenic oocyte, CA – cortical alveoli oocyte, EVTG – early vitellogenic oocyte, PG – primary growth oocyte.

Credit

Gkenas, C., Sequeira, V., Ribeiro, D., Gago, J., Dias, D., Verma, C.R., Kumkar, P. and Ribeiro, F.