Crayfish are fascinating animals and capable of a wide spectrum of behaviors. Keeping them in aquaria is a rewarding way of learning more about them and an interesting alternative to ornamental fish. Since the mid-1990s, the popularity of crayfish as ornamental pets has strongly increased.
Selection of crayfish species available through the European pet trade: A – Procambarus clarkii (white color morph); B – Cherax pulcher; C – Cherax destructor (blue color morph); D – Cherax peknyi; and E – Procambarus llamsi
However, this trend has its downsides:
The majority of crayfish species make actually pretty bad pets: they are mostly nocturnal and, due to omnivorous feeding habits, can quickly degrade a typical aquarium community, including grazing and uprooting of plants and preying on fish.
Many species, in particular larger Procambarus spp., are very prolific and can rapidly overpopulate aquaria.
Some of the offered species can rapidly outgrow their tanks, e.g., Cherax quadricarinatus.
Aquarium hobbyists are therefore likely to want to offload unwanted crayfish or excess stock into nature. In fact, ongoing releases from aquaria drive the establishment success of Marmorkrebs in Europe and likely contribute to invasions of other alien crayfish species as well. Overall, the pet trade has become a novel pathway for alien crayfish species introductions.
Marmorkrebs (Procambarus fallax f. virginalis) epitomize the risk of crayfish invasions from aquaria. All global Marmorkrebs introductions most likely trace back to the first occurrence of this species in the German pet trade in the mid-1990s
A recent study showed that the likelihood of becoming introduced from aquaria largely depends on a crayfish species’ size and availability: large species that are widely available through the aquarium trade are likely to be introduced into nature!
For this reason, if you are interested in keeping crayfish in aquaria (which is inherently no bad thing), please act responsibly and keep and breed only low-risk species. In Central Europe, low-risk species include most Cherax spp. from Irian Jaya (the western part of New Guinea), most dwarf crayfish (Cambarellus spp.), and native Noble crayfish. Please do not breed any high-risk species, including P. clarkii, Marmorkrebs, and most Orconectes spp., as any proliferation of these species increases the risk of further harmful introductions into nature.
Cherax peknyi is a colorful crayfish species from Irian Jaya. Apart from its nocturnal lifestyle and propensity to burrowing, this species is rather docile in an aquarium environment
Equally concerning is stocking of alien crayfish into garden ponds. Crayfish readily leave garden ponds and can migrate great distances over land. There are numerous examples of alien crayfish found in residential areas that most likely escaped from garden ponds. If you want to keep crayfish in your garden pond, please do exclusively stock native crayfish. In this context: please be aware of falsely labeled crayfish in the pet trade or online market places; especially alien Signal crayfish and Narrow-clawed crayfish are frequently offered as native Noble crayfish.
Crayfish (here P. clarkii) are notorious escapees – alien crayfish species should be never kept outdoors
Chucholl, C., Morawetz, K., Groß, H. (2012). The clones are coming – strong increase in Marmorkrebs [Procambarus fallax (Hagen, 1870) f. virginalis] records from Europe. Aquat. Invas. 7: 511–519
Chucholl, C. (2013). Invaders for sale: trade and determinants of introduction of ornamental freshwater crayfish. Biol. Inv. 15: 125–141
Papavlasopoulou, I., Perdikaris, C., Vardakas, L., Paschos, I. (2013). Enemy at the gates: introduction potential of non-indigenous freshwater crayfish in Greece via the aquarium trade. Cent. Eur. J. Biol. DOI: 10.2478/s11535-013-0120-6
Soes, M., Koese, B., (2010). Invasive crayfish in the Netherlands: a preliminary risk analysis. Interim report, Bureau Waardenburg bv, Stichting EIS-Nederland, Invasive Alien Species Team, Waardenburg, 69 p.
www.marmorkrebs.org (website about Marmorkrebs maintained by Zen Faulkes, featuring a map of worldwide Marmorkrebs introductions)