28 November 2022

Georgia bans Marmorkrebs

Map of USA showing location of state of Georgia
The One Green Planet site is reporting that the southern US state of Georgia has announced plans to ban Marmorkrebs.


The ban would take effect 4 December 2022. A perusal of a public announcement from the Georgia Department of Natural Resources (PDF) seems to show that keeping almost any other crayfish species – except Louisiana red swamp crayfish (Procambarus clarkii) and White river crayfish (Procambarus zonangulus) – would require a permit.


The state and provincial regulations seem to be picking up steam. But I continue to worry about whether these bans are taking into account that there might be researchers who might want to study these animals for scientific purposes.

External links

Georgia Department of Natural Resources Subject 391-4-8 Wild Animals (PDF)

Georgia finally expands restrictions on wild animals as pets

Map by TUBS - This SVG locator map includes elements that have been taken or adapted from this locator map:, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15948353

04 November 2022

Minnesota eyes Marmorkrebs ban

 Read the story here.

02 November 2022

Gallardo and colleagues, 2022

Cover to Journal of Applied Ecology
Gallardo B, Sutherland WJ, Martin P, Aldridge DC. 2022. Applying Fault Tree Analysis to biological invasions identifies optimal targets for effective biosecurity. Journal of Applied Ecology 59(10): 2553-2566. https://doi.org/10.1111/1365-2664.14256




  1. The management of invasive species requires analytical tools that can synthesise the increasing and complex information generated through risk assessment protocols. To that end, fault tree analysis (FTA) provides a means to conceptually map all of the events leading to a particular undesired scenario with associated probabilities and uncertainty.
  2. We used a peer-reviewed dataset (the GB Non-Native Species Risk Assessments) to build and quantify a FT of all the events leading to the transport, introduction, establishment and spread of harmful aquatic invasive species in Great Britain. We also simulated management scenarios.
  3. Individual barriers to invasion, either natural or human, were largely unsuccessful in hindering invasion (42%–91% probability of failure in a 5-year period); yet the high interdependence of events in the tree resulted in an overall probability of harmful invasion of about 3%. This figure is much greater than that estimated by the tens rule, which posits that 10% of non-native species manage to colonise a new area, and only 10% of those become invasive, resulting in a 1% overall probability of harmful invasion.
  4. We used the FTA to explore different management intervention scenarios and found that pre-border management reduced the overall risk of invasion by 86%, followed in importance by early action after introduction (85%), and detection at the border (81%). In contrast, post-establishment management techniques, such as eradication and containment, had a limited impact reducing the probability of widespread invasion (18%–24%).
  5. Synthesis and applications. While prevention has been long recognised as the most cost-effective action against biological invasions, here we were able to quantify the reduction in invasion risk under a range of management scenarios. Optimising all management elements included in the FT reduced the overall probability of invasion by three orders of magnitude.
  6. We conclude that FTA provides a baseline to capitalise on a growing source of peer-reviewed risk assessments, which allows systematic assessment of the effectiveness of future actions to prevent and manage invasive species at the national and international levels. The analytical framework can be extended to other biological threats (e.g. pests, pathogens, diseases) and scenarios (e.g. climate change, war), so that breach and leverage points in biosecurity can be identified.

 Keywords: None provided.

Open access

Dobrović and colleagues, 2022

NeoBiota logo
Dobrović A, Geček S, Klanjšček T, Haberle I, Dragičević P, Pavić D, Petelinec A, Boštjančić LL, Bonassin L, Theissinger K, Hudina S. 2022. Recurring infection by crayfish plague pathogen only marginally affects survival and growth of marbled crayfish. NeoBiota 77: 155-177. https://doi.org/10.3897/neobiota.77.87474




Invasive alien crayfish threaten the diversity of freshwater ecosystems and native crayfish fauna. In Europe, this is largely due to transmission of the crayfish plague to susceptible native crayfish. Many invasive species tolerate crayfish plague, but the infection still has the potential to reduce the fitness of a tolerant host due to energy trade-offs between immune response maintenance and life-history traits, such as growth and reproduction. In combination with other unfavourable conditions, such a response could alter further invasion success of an otherwise successful crayfish invader. We examined whether repeated infection with one of the most virulent haplogroups of crayfish plague agent (Aphanomyces astaci) affects growth or survival of the juvenile marbled crayfish (Procambarus virginalis). Juveniles were exposed to i) two levels of pathogen concentrations, and ii) two different feeding regimes under the higher pathogen concentration. In all performed trials, repeated infection reduced growth rates, while the combination of recurring infection and food limitation significantly increased mortality. The average energy cost of the immune response was estimated at 12.07 J/day for individuals weighing 0.3 grams. Since infections were frequent and pathogen concentrations high, results suggest that marbled crayfish is resistant to A. astaci pathogen and its survival is only affected by adding the stress of food limitation. The survival of almost half of the individuals exposed to high pathogen loads and extreme food limitation indicates that chronic infection by crayfish plague is unlikely to be an important factor impeding invasion success of the marbled crayfish, even under harsh conditions. Our results add to the growing body of evidence that marbled crayfish has potential to become one of the most successful freshwater invaders.


Keywords: food limitation • freshwater • immunity cost • infection • invasive species • trade-off

Open access