Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).
First reported in the wild
Invasive species - risk of High Impact
Introduction pathways - 1
Introduction pathways subclass - 1
Ship/boat ballast water
NAPRA Ireland risk assessed
Yes. This species underwent a Non-native species APplication based Risk Analysis in 2014.
Overall risk of this species to Ireland is categorised as: MAJOR with a HIGH level of confidence.
Overall conclusion summary: Corbicula fluminea is considered to pose a major risk to native biodiversity, native ecosystems and conservation goals as well as having the potential to cause negative socio-economic impacts due to its capacity to spread rapidly and establish dense populations.View the full risk assessment:
Small freshwater bivalve mollusc, usually less than 25mm in diameter with a thick shell marked with evenly space concentric ridges, yellow to olive brown in colour (Booy et al., 2015).
Due to the recent arrival the effects of Asian clams in Irish river systems have yet to be fully studied and are likely to be dependent on a number of factors, including habitat invaded, density of invasion and the biotic community present. Freshwater bivalves tend to function as ecosystem engineers (organism that changes the biotic or abiotic environment in which it lives) (Sousa et al., 2009; Vaughn & Hakenkamp, 2001) and Asian clams can occur in extremely high densities and giving them the potential to change the ecological characteristics of invaded areas (Ceffrey et al., 2001; Lucy et al., 2012; Minchin, 2014; Sousa et al., 2009. They can filter large volumes of water in short periods of time, improving water clarity while depositing large amounts of organic matter on the bottom (Lucy et al., 2012), potentially leading to an increase in fish catches while subsequently damaging spawning beds. They shells provide a substrate for certain macroinvertebrates, while competing with other species for food (Sousa et al., 2008). Additionally they compete with other bivalves, such as the Freshwater pearl mussel (Margaritifera margaritifera), and macrophytes (aquatic plants large enough to be seen with the naked eye) for space.
Inland surface waters
Hermaphrodite, with fertilisation occurring internally before the release of small juveniles with a completely developed foot, with maturation occurring in 3 to 6 months (Sousa, et al. 2008). Low juvenile and adult survivorship is offset by high fecundity (number of offspring produced) (>68,000 pediveligers per adult per year)(Lucy et al., 2012) and a rapid growth rate (Sousa et al., 2008).
Pathway and vector description
Originally a single individual was found in the river Barrow, Co Carlow in April 2010 (Sweeney, 2009), with the shell thought to be 2 years old putting an introduction date at 2008. Introduction into Ireland is likely to have been from overland transportation of leisure craft from the Britain (Minchin, 2014), where Asian clam has been present since 1998 (Booy et al., 2015), either as a fouling organism on hulls or carried in bilge water. Populations found in the Shannon suggest as many as 4 subsequent introductions and likely future spread will be through leisure craft and angling/fishing equipment (Minchin, 2014). They may also be spread by the movement of fish, both natural and restocking programs, as they have been shown to survive in passage through the gut (Gatlin, et al. 2013).
Mechanism of impact
Competition, Predation, Bio-fouling, Interaction with other invasive species, Other
Found buried in or resting on the sediment in lakes and rivers, high variation in densities were found moving from upstream to downstream in the river Barrow (8-147 per metre squared upstream; 1,300 to 9,636 per metre squared 1km downstream; 732 to 1,196 per metre squared 5km downstream) (Caffrey et al., 2011).
Temperate Asia, Tropical Asia, Africa, Australasia
Established - Widespread. It was initially discovered in the rivers Nore and Barrow but has since been found in the Shannon river system at Lough Derg and Carrick on Shannon. Possibly present elsewhere but not recorded. Only 0.9% of Irish rivers and 2.1% of lakes have a pH unsuitable for this species (Lucy et al., 2012).
Originally native to southern & eastern Asia (Booy et al., 2015).
Date of first record category
Fifty year date category
Records submitted to Data Centre in 2022
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
Report any sightings to the National Biodiversity Data Centre or Inland Fisheries Ireland. Obey good biosecurity practices: Check and clean leisure craft when moving from areas containing Asian clams to uninfected river systems; disinfect fishing/angling equipment; disinfect boats when moving from one river catchment to another or upstream within river systems.
Delivering Alien Invasive Species In Europe (DAISIE) project list this as one of the 100 Worst Invaders in Europe.
Booy, O., Wade, M. & Roy, H. (2015) Field Guide to the Invasive Plants & Animals in Britain. Bloomsbury. Vaughn, C. C., & Hakenkamp, C. C. (2001). The functional role of burrowing bivalves in freshwater ecosystems. Freshwater Biology, 46(11), 1431-1446.
Caffrey, J.M., Evers, S., Millane, M. and Moran, H. (2011). Current status of Ireland’s newest invasive species – the Asian clam Corbicula fluminea (Müller, 1774). Aquatic Invasions 6, Issue 3:291–299.
Gatlin, M. R., Shoup, D. E., & Long, J. M. (2013). Invasive zebra mussels (Driessena polymorpha) and Asian clams (Corbicula fluminea) survive gut passage of migratory fish species: implications for dispersal. Biological invasions, 15(6), 1195-1200.
Lucy, F.E., Karatayev, A.Y. and Burlakova, L.E. (2012). Predictions for the spread, population density, and impacts of Corbicula fluminea in Ireland. Aquatic Invasions 7(4):465-474.
Minchin, D. (2014). The distribution of the Asian clam Corbicula fluminea and its potential to spread in Ireland. Management of Biological Invasions 5(2): 165-177.
Sousa, R., Gutiérrez, J. L., & Aldridge, D. C. (2009). Non-indigenous invasive bivalves as ecosystem engineers. Biological Invasions, 11(10), 2367-2385. Chicago
Sweeney, P. (2009). First record of Asian clam Corbicula fluminea (Müller, 1774) in Ireland. Irish Naturalists’ Journal 30(2):147–14.