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

Scope

Description and general ecology

Impacts

Distribution and basic metrics

Control options

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

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

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

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

Corbicula fluminea – Impacts

High density and high filtration rate (up to 1 litre per hour) will alter trophic and nutrient dynamics

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

Efficient ecosystem engineer – altering the structure and function of invaded habitats

High filtration capacity will increase water clarity

Corbicula fluminea – Impacts

Macro-fouling of pipes

Efficient ecosystem engineer – altering the structure and function of invaded habitats

Clog gravels and interfere with spawning for salmon and trout

Uproot and displace native mussels (including protected species)

Increase flood hazard as shells accumulate by reducing discharge capacity

blocking sluice gates, pipes… Impact navigation by shallowing channels; increase dredging episodes

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

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

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

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

2 3 4

Age

10

15

20

25

30

Sh

ell

len

gth

Asian clam – Size & Age Class

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

Asian clam – Control Options

Determine national distribution and scale of problem

Issue alerts to public and stakeholders

Seek funding

Proposed Action Plan

Asian clam – Control Options

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)

Proposed Action Plan

Corbicula is susceptible to anoxia High mortality recorded beneath barriers in Lake Tahoe and Lake

George (USA)

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)

Benthic Barrier Trials in River Barrow 2010/2011

Trials commenced using jute matting and plastic in December on River Barrow

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)

Asian clam – Control Options

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

Proposed Action Plan

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

Asian clam – Control Options

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

Proposed Action Plan

Will we eradicate Corbicula from Ireland?

Probably not!

but research may enable us to deal with invasions into new and sensitive habitats

Thanks to

NPWS

Heritage Council

IFI SERBD

EU Life+ CAISIE project