Invasive Characteristics and Control Options for Asian Clam ( Corbicula fluminea) in Ireland

1. Invasive Characteristics and Control Options for Asian Clam (Corbicula fluminea) in Ireland Dr Joe Caffrey Inland Fisheries Ireland ISI Forum, Belfast Museum – 20th April 2011

2. Scope Description and general ecology Impacts Distribution and basic metrics Control options

3. Corbicula fluminea – Description Yellow-brown (to black) bivalve Shell has concentric, evenly-spaced, thick ridges Usually < 25 mm but can grow to 50 mm in length

4. Corbicula fluminea – Habitat Freshwater: lakes, canals, rivers and streams Common in tidal sections of large rivers but ….. Intolerant of pollution Intolerant of low dissolved oxygen conditions Tolerant of low salinity brackish water (5 – 8 ppt) Sand and small gravel habitats, but flexible

5. Corbicula fluminea – Life Cycle Hermaphrodite, capable of cross- and self-fertilisation Reproduce in spring and autumn Can produce up to 70,000 juveniles per annum Juveniles fully formed on release, with a single mucilaginous byssal thread Maturity occurs at 3 – 12 months Adult life span is variable, spanning 1 – 5 years

6. Corbicula fluminea – Vectors for Spread Food item Angling bait Aquarium dump Water craft - bilge water, sediment on anchor, juveniles byssally attached to boat hulls…. In dredged river gravel or soil Byssal thread attachment to water fowl, floating debris or vegetation Water movement in natural systems

8. Corbicula fluminea – Impacts Efficient ecosystem engineer – altering the structure and function of invaded habitats High density and high filtration rate (up to 1 litre per hour) will alter trophic and nutrient dynamics High filtration capacity will increase water clarity Compete with other filter feeders for limited food resources Compete with other mollusc species by pedal feeding in sediment Accelerate deposition of organic matter, altering substrate composition

9. Corbicula fluminea – Impacts Efficient ecosystem engineer – altering the structure and function of invaded habitats Macro-fouling of pipes Increase flood hazard as shells accumulate by reducing discharge capacity blocking sluice gates, pipes… Impact navigation by shallowing channels; increase dredging episodes Clog gravels and interfere with spawning for salmon and trout Uproot and displace native mussels (including protected species)

10. Corbicula fluminea – Distribution Native to southern and eastern Asia, Australia and Africa Introduced into North America in early 1900s Now present in 38 States Introduced to Europe in 1980 – first records in eastern France and Portugal By 2000 present in most major watersheds on the European mainland First record in Britain in 1998 (Norfolk Broads) and in River Thames in 2004

11. Distribution in Ireland 2010 - 2011 First record in River Barrow April 2010, at St Mullin’s Distribution determined (SCUBA) in Barrow and Nore in June/July 2010 None above tidal reaches River Suir surveyed in September 2010

12. Corbicula – Density Location No./sq m Max. No./sq m St Mullin’s, Barrow 96.8 + 21 146.8 Scar, Barrow 5,742.6 + 2,409 9,636 Poulmounty, Barrow 964 + 232 1,196 River Nore 320 + 9 336

13. Corbicula in River Barrow at Scar (d/s St Mullin’s)

14. Asian clam – Size & Age Class

15. Distribution in Ireland 2010 - 2011 Recorded in Carrick-on-Shannon in September 2010 present over 15 km long section Recorded in Lough Derg in January 2011

16. Asian clam – Control Options Proposed Action Plan Determine national distribution and scale of problem Issue alerts to public and stakeholders Seek funding

17. Asian clam – Control Options Proposed Action Plan Determine national distribution and scale of problem Issue alerts to public and stakeholders Seek funding Study habits and reactions to toxins in vivo (with QUB) Suction dredge (poss. use cockle harvester) Benthic barriers – biodegradable jute / plastic or rubber mats Benthic barriers and chemical additives (e.g. salt)

18. Benthic Barrier Trials in River Barrow 2010/2011 • Corbicula is susceptible to anoxia • High mortality recorded beneath barriers in Lake Tahoe and Lake George (USA)

19. Benthic Barrier Trials in River Barrow 2010/2011 • Corbicula is susceptible to anoxia • High mortality recorded beneath barriers in Lake Tahoe and Lake George (USA) Trials commenced using jute matting and plastic in December on River Barrow

20. Benthic Barrier Trials in River Barrow 2010/2011 Barriers laid in adverse conditions – cold and flood events Most barriers were disturbed by tidal flows and floods Results inconclusive Will recommence trials in May with QUB Site visit planned by scientist leading work in Lake George (USA)

21. Asian clam – Control Options Proposed Action Plan Determine national distribution and scale of problem Issue alerts to public and stakeholders Seek funding and support Study habits and reactions to stimuli / toxins in vivo Suction dredge (poss. use cockle harvester) Benthic barriers – biodegradable jute / plastic or rubber mats Benthic barriers with chemical additives (e.g. salt) Biobullet

22. Biobullet Treatment Encapsulates toxins within edible coating, giving efficient and targeted control to Corbicula Toxin is concentrated by Corbicula as it filter feeds Anything not ingested degrades to harmless concentrations within 1 hour of entering water Approved for use in drinking water Collaboration with Univ of Cambridge to commence in May 2011

23. Asian clam – Control Options Proposed Action Plan Determine distribution and scale of problem Draw up Risk Register Seek funding and support Distribute Alerts and create awareness Study habits and reactions to stimuli in vivo Suction dredge Benthic barriers Benthic barriers with chemical additives (e.g. salt) Biobullet Any other ideas

24. Will we eradicate Corbicula from Ireland? Probably not! but research may enable us to deal with invasions into new and sensitive habitats

25. Thanks to NPWS Heritage Council IFI SERBD EU Life+ CAISIE project