The Destructive Presence of the Australian Crayfish in Ireland: The Yabby
By Babette Bookelaar
Irish native white-clawed crayfish (Austropotamobius pallipes) are under threat due to the appearance of a non-native crayfish species, the Australian yabby (Cherax destructor).
Worldwide there are approximately 650 different crayfish species, but only 6 of those species are native to Europe and the white-clawed crayfish (Austropotamobius pallipes) is the only native crayfish species in Ireland (1). Freshwater crayfish look similar to small brown lobsters and live in Ireland’s rivers, streams and lakes.
It is known that non-native crayfish species have been held in aquariums in Ireland, while it is illegal to keep, breed and sell those species in Ireland.
The Australian native crayfish, also known as the yabby, (Cherax destructor) (Figure 1) is a potential threat if released into the Irish environment. The presence of invasive species can greatly reduce the level of biodiversity in a habitat, by out competing the native species. Therefore legislation is often put in place to reduce the risk of the most invasive species (7).
A study in 2015 concluded that certain invasive crayfish, including the yabby, can withstand low winter temperatures equal to habitats in the European temperature zone. It also seemed to have a higher reproductive rate, burrowing behaviour, and wider range of tolerance to environmental conditions compared to native species. These characteristics make the species a very serious threat to European ecosystems (5). Indeed, the appearance of the Australian yabby has been marked as a significant factor in the decline of the white-clawed crayfish (2).
It has been confirmed in recent years that the Australian yabby has been detected in an Irish ecosystem, the Ballyhass Lakes. The Ballyhass Lakes are 2 separate lakes (one main and one smaller lake) created by overflooding a former unused quarry. The lakes have 36 acres of surface, fed by a thermal spring and protected from strong winds (3). Since 1998 Ballyhass has operated as a commercial fishery for rainbow and brown trout and functions as a successful angling centre. Nowadays, Ballyhass is well known for its additional activity centre covering a variety of water sports.
In May-June 2019 more than 1800 Australian yabbies were caught in the main lake, while none were caught in the smaller lake. Both females and small juveniles were identified. Spawning requires water temperatures above 15 °C (7). Temperature logs indicated that water reached up to 18°C during the summer of 2019 in Ballyhass, with no thermal stratification. These circumstances in water temperature could explain the reproductive population of the Australian yabby.
The legislation; No. 354/2018 – European Union (Invasive Alien Species) (Freshwater Crayfish) Regulations 2018, covers information over importing and keeping of non-native crayfish species. The list of five non-native species in this legislation are: spiny-cheek crayfish (Orconectes limosus), virile crayfish (Orconectes virilis), signal crayfish (Pacifastacus leniusculus), red swamp crayfish (Procambarus clarkii) and marbled crayfish (Procambarus fallax virginalis). It is illegal to keep, breed, import, sell, or release those species into the wild. However, there is no legislation for the Australian yabby yet.
What can you do to reduce the risk of non-native crayfish species:
- Don’t take foreign crayfish into the country.
- Don’t release any aquarium bred crayfish into the wild.
- If you have your own pet shop, don’t buy or sell any crayfish species.
- Always clean and dry fishing gear when transferring between different water bodies.
- If you can’t dry your gear, try to disinfect with a dilute bleach solution.
- Don’t farm native crayfish species with fish species.
- If anyone comes across a non-native species it is recommended to contact the National Parks and Wildlife Service (4).
If you want to report any concerns about a non-native crayfish species then you can contact NPWS by email: natureconservation@environ.ie
References
- Lysaght, L, (Unknown year) ‘Austropotamobius pallipes | Freshwater White-clawed Crayfish, Biodiversity Ireland. Available at: https://species.biodiversityireland.ie/profile.php?taxonId=17487#Taxonomy (Accessed: 1 September 2021)
- Department of Culture, (2019) Heritage and the Gaeltacht, ‘NPWS calls for public support in dealing with Invasive Species and Disease, Biodiversity Ireland, Available at: https://www.biodiversityireland.ie/npws-calls-for-public-support-in-dealing-with-invasive-species-and-disease/ (Accessed: 1 September 2021)
- Sweeney, P. (2020) Yabbies in Cork, Freshwater Science, available at: https://freshwaterscience.ie/wp-content/uploads/2020/04/Sweeney-Pascal-presentation-2020.pdf (Accessed: 31 Aug 2021)
- Reynolds J.D. and O’Keeffe C. (Unknown Year). NPWS, available at: https://www.npws.ie/sites/default/files/publications/pdf/Crayfish_leaflet.pdf (Accessed: 31 August 2021)
- Veselý L, Buřič M and Kouba A. (2015) Hardy exotics species in temperate zone: can “warm water” crayfish invaders establish regardless of low temperatures? Sci Rep. 17;5:16340. doi: 10.1038/srep16340. PMID: 26572317; PMCID: PMC4648075. Available at: https://www.cabi.org/isc/datasheet/89134#tosummaryOfInvasiveness (Accessed: 2 September 2021)
- EPA Catchment Units. (2019) Catchments. Crayfish Plague spreading in our river catchments. Catchment Management, News, Water and Communicities, Water Framework Directive. Available at: https://www.catchments.ie/crayfish-plague-spreading-in-our-river-catchments/ (Accessed: 1 September 2021)
CABI. (2011) Cherax destructor (yabby), Invasive Species Compendium,. Available at: https://www.cabi.org/isc/datasheet/89134 (Accessed: 1 September 2021)
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