Marmorkrebs, also called marbled crayfish, are a species that is thought to have been created during breeding of Procambarus fallax in captivity for the purpose of the aquarium trade. There are no known indigenous populations of marmorkrebs, however, it has been discovered in natural systems in Germany, Italy, the Netherlands, and the island of Madagascar.
Marmorkrebs are unique in that the population is exclusively females and they reproduce via cloning. If introduced, they could be easily confused with other native species of crayfish in Ontario.
The marmorkreb is capable of living in a wide variety of habitats, such as rivers, lakes, swamps, drainage ditches, and fish ponds. It doesn’t seem to differentiate between fast- or slow-moving water and substrate types. There are currently no known populations in the wild in Ontario.
Impacts of Marmorkrebs
- By eating aquatic vegetation, they reduce spawning and nursery habitat for native fish.
- Possesses the ability to degrade wetland habitat, which has been observed in its introduced range.
- Could reduce native crayfish populations through direct competition as well as through the potential spread of disease.
- Due to the marmorkrebs’ ability to clone, the introduction of a single female could establish a new population.
How to Identify Marmorkrebs
- Medium-sized crayfish.
- Capable of reaching 13 cm, but is usually less than 10 cm.
- Distinct marble coloured pattern, especially on the latter parts of the carapace.
- Usually olive or dark brown but can range from tan to reddish to blue.
- Relatively small chelae (claws) in contrast to other native species. Usually less than half the length of the carapace, with an elongated palm.
What You Can Do
- Learn how to identify marmorkrebs and how to prevent accidentally spreading invasive species.
- If you want to use crayfish as bait, you may only use them in the waterbody in which they were captured. For more information on using crayfish as bait, check the Ontario Fishing Regulations.
- If you have any information about the release of species, such as the marbled crayfish, into Ontario’s waters, report it immediately to the MNRF TIPS line at 1-877-847-7667 toll-free any time, or contact your local Ministry of Natural Resources and Forestry office during regular business hours. You can also call Crime Stoppers anonymously at 1-800-222-8477.
- If you find a marbled crayfish or other invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, visit EDDMapS Ontario, or search for the ‘Invasive Species in Ontario’ project on iNaturalist.org to report a sighting.