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Control Alternatives for Dams and Water Impoundments. Robert F. McMahon Center for Biological Macrofouling Research Department of Biology The University of Texas at Arlington. DAM STRUCTURES FOULED BY ZEBRA MUSSELS. Structures Problems

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Control Alternatives for Dams and Water Impoundments

Robert F. McMahon

Center for Biological Macrofouling Research

Department of Biology

The University of Texas at Arlington


Structures Problems

Dam Gates: Abrasion of seals, increased weight, corrosion, prevention of operation

Dam Gate Interiors: Increased weight, corrosion

Drains: Blockage of flow

Pier Nose: Poor flow distribution

Wickets: Prevention of Operation

Structures Problems

Conduits, Culverts Reduction of flow, corrosion

and Piping:

Valves: Interference with operation,

cavitation, seat damage

Water Quality Wet Prevention of operation due to Wells: fouling by mussels

Trash Booms: Submergence due to increased weight, corrosion


Structures Problems

Navigation Submergence due to increased Buoys: weight, corrosion

Public Beaches: Accumulating shells may cut

or abrade the skin of swimmers, odors of decaying mussels

Boating and Fouling of engine cooling and hulls


Shore Structures: Submergence due to increased weight, corrosion, interference with operation

Structures Problems

Aquatic Ecology,Impacts on species diversity, Trophic Dynamics,fisheries, food chain dynamics, Energy Flow:unionid mussels, water clarity, productivity, growth of macrophytic vegetation and sedimentation rates





Dam Gates: Manual removal; toxic, metallic and foul-release coatings; disposable substrata; thermal treatment; cathodic protection; periodic operation; desiccation; robotics

Dam Gate Interiors: Manual removal; hydroblasting, toxic, metallic and foul-release coatings; disposable substrata; thermal treatment; desiccation; freezing

Drains: Manual removal, toxic, metallic and foul-release coatings; robotics; thermal treatment; desiccation; freezing; hydroblasting

Pier Nose: Disposable substrata; toxic, metallic and foul-release coatings; cathodic protection; air bubbler systems; desiccation; freezing

Wickets: Toxic, metallic, or foul-release coatings; thermal treatment; manual removal; disposable substrata; under water hydroblasting; periodic operation

Rubber Side Seals on Gates: Periodic operation; manual removal; air bubbler systems; thermal treatment; emersion

Roller Gate Tracks: Manual removal; periodic operation; cathodic protection

Chains and Cables: Manual removal; periodic operation

Slots: Manual removal; inserts; periodic operation; toxic and metallic coatings

Trash Racks: Manual cleaning; toxic and metallic coatings; make readily removable and exchangeable; thermal treatment; cathodic protection; disposable substrata; robotics

Conduits, Culverts and Piping: Manual cleaning; line pigs; toxic and metallic coatings; hypoxia/anoxia; desiccation; heated air; thermal treatment

Valves: Periodic operation; manual cleaning; construction with toxic metals; thermal treatment; desiccation; heated air; thermal treatment

Water Quality Wet Wells: Manual cleaning; toxic or metallic coatings; molluscicides; thermal treatment; desiccation; heated air; hypoxia/anoxia

Trash Booms: Manual cleaning, toxic, metallic or foul-release coatings; alternate replacement


Navigation Buoys: Manual cleaning; toxic, metallic or foul-release coatings; alternate replacement; hydroblasting

Public Beaches: Manual removal; design of removal equipment?

Boating and Vessels: Manual cleaning; toxic or metalliccoatings; hydroblasting; robotic hull cleaners

Shore Structures: Manual cleaning; metallic or foul-release coatings; hydroblasting; robotics; disposable substrata; desiccation; thermal treatment; freezing



Complete eradication of zebra/quagga mussels from large water bodies has not been accomplished reduction in population densities may be possible

Why is Eradication Difficult?

  • Treatment has to be targeted to affect only mussel populations

  • Volume of water to be treated is generally very large

  • Environmental impacts of the treatment must be acceptable

  • Costs may be prohibitive

Reduction in Population Densities

  • Could be achieved under some circumstances

  • Minimizes abiotic and biotic impacts of mussel infestation

  • Reduces dam structure and raw water using system mussel impingement rates

  • Lessens impact on nontarget species

  • More cost effective than direct control



Water Level Drawdown: Periodic level reduction to below usual thermocline to expose mussel populations to summer high temperature, desiccating or winter freezing conditions

Predators: Fish; diving ducks; crayfish; muskrats; molluscivorous fish stocking programs (requires further development)

Parasites: Targeted against zebra mussels to control population densities; native or introduced (in early research stage); may require extensive permitting for use

Disease Organisms: Bacterial or viral disease vectors specific to zebra mussels utilized to control population densities (in early research stage)

Microbial Toxins: Chemical agents developed from bacteria or algae that are toxic to mussels (early stages of development – no commercial products available)

Time: Given enough time zebra mussls populations may decline to levels that reduce their impacts on lake/impoundment infrastructure and ecology

Planned Water Level Draw Downs Exposing Mussels to Desiccating or Freezing Conditions

  • Planned water level draw downs in order to emerse mussels in air

  • Summer emersion and desiccation (<10 Days)

  • Temperature and humidity dependent responses

  • Recreational and water user considerations

  • Winter freezing (< 1 day)

  • Tolerance time decreases with decreasing subfreezing temperature

  • Recreational and water user considerations

Fish Predators of Zebra Mussels Desiccating or Freezing Conditions

Family Genus and Species Common Name

ClupeidaeAlosa sapidissima American Shad●

CyrinidaeCyrinus carpio Common Carp●

CatostomidaeIctibius bubalus Smallmouth Buffalo Ictobius niger Black Buffalo Minytrema melanopus Spotted Sucker Moxostoma carinatum River Redhorse

PercichthyidaeRoccus saxatilus Striped Bass

IctaluridaeIctalurus furcatus Blue Catfish Ictalus punctatus Channel Catfish ●CentrachidaeLepomis gulosus Warmouth Lepomis macrochirus Bluegill Lepomis microlophus Red Ear Sunfish ●

SciaenidaeAplodinotus grunniens Freshwater Drum ●

AcipenseridaeAcipenser fulvesens Lake Sturgeon

PerchidaeGymnocephalus cernuus Ruffe ●●

GobiidaeNeogobius melanostomus Round Goby●●

●Greatest potential for controlling zebra mussels

●Nonindigenous species in the Great Lakes

Bird Predation for Control of Zebra Mussels Desiccating or Freezing Conditions

  • Diving duck and coot predation on zebra mussels is reported to reduce population densities by as much as 90% in some European Lakes

  • Diving ducks reduce Asian Clam densities by 67-80% in North America

  • Diving ducks feed on zebra mussels in western Lake Erie

  • Degree to which Diving ducks regulate the density of Lake Erie mussel populations is unknown

  • Ducks do not appear to be regulating mussel densities in North America

Other Predators Potentially Capable of Desiccating or Freezing Conditions

Regulating Zebra Mussel Densities

  • Crayfish

  • In Europe, Orconecteslimosus averaging 90 mm long ate 93-114 juvenile mussels/day

  • In N. A., crayfish feed on Asian clams

  • Degree that crayfish could regulate N.A. zebra mussel populations is unknown

  • Muskrats

  • Have reduced native bivalve populations in N.A.

  • Effects on zebra mussels are unknown

Parasites Desiccating or Freezing Conditions

  • There are a number of bivalve parasites

  • Ciliates and Acetosporanprotozoans

  • Bacteria

  • Nematodes

  • Trematodes

  • Olicochaetes (Chaetogasterlimnaei)

  • Hirudinea (leeches)

  • Unionicolid Mites

  • Capacity of parasites to regulate zebra mussel densities is unknown

  • No reports of major reductions in zebra mussel population densities due to parasites in N.A. or Europe

Diseases Desiccating or Freezing Conditions

  • Bivalve population densities have been reduced by infectious diseases

  • Bacteria (Vibrio and Pseudomonas) cause mass mortalities in oysters

  • Such bacteria are not reported in zebra mussels

  • Acetosporan, Haplosporidiumnelsoni(MSX) reduces oyster populations by up to 95%

  • Similar Acetosporan-like infections occur in zebra mussels but do not induce mass mortalities

  • No known viral diseases inducing massive mortalities in zebra mussel populations

  • If identified, a disease organism could produce targeted control of mussel density in impoundments

Targeted Bacterial Toxins Desiccating or Freezing Conditions

  • Many bacterial species produce toxins that are relatively specific in their lethal effects

  • Can be effective in controlling invasive species populations at very low concentrations

  • If discovered, could allow targeted treatment of natural waters without greatly affecting other biota

  • Requires extensive research to screen for potentially effective bacterial toxins

  • Bacterial toxins have been discovered which induce mortality in zebra/quagga mussels

  • Soil-water bacterium, Pseudomonas floresens(Molloy 1998)

  • Four bacterial isolates from stressed mussels (Ji-Dong et al. 1994)

  • Successful control applications have not been demonstrated in natural environments

  • May not prove to be practical or cost-effective

Time Desiccating or Freezing Conditions

  • Exotic species often exhibit a massive population explosion immediately after invading a new habitat

  • As resources are used up, population densities often decline to much lower levels

  • Period for density decline is variable

  • 2-50 years depending on species

  • Asian clams have experienced major density declines in N.A. 15-20 years after invasion

  • High densities occur only in new areas of invasion

  • The zebra mussel population in Lake Oologah, OK, was extirpated in the summer of 2008 after several years of continual decline (McMahon, personal observation)

  • The quagga mussel population in the 1000 Islands region of the St Lawrence River appears to be in decline (McMahon, personal observation)

Time (cont.) Desiccating or Freezing Conditions

  • Zebra mussels have experienced similar major population declines throughout Europe

  • High densities only in newly invaded habitats in the Netherlands, Sweden and Russia

  • Now have little impact in most European habitats where they were once very dense

ERADIATION FROM IMPOUNDMENTS Desiccating or Freezing Conditions


  • Complete eradication of established zebra/quagga mussel may be possible in small isolated water bodies

  • Millbrook Quarry Lake experience in Virginia

    • 12 surface acres, 93 ft deep

  • Lake did not have a flowing outlet

  • Entire lake treated with potash (potassium chloride)

    • 174,000 gal of KCl solution – target concentration of 100 mg/l

  • Aeration used to mix lake water across depth

  • Monitored KCl levels throughout lake – potash applied until lethal levels were achieved throughout

    • 98-115 mg KCl achieved throughout

  • Used live mussel samples to check for 100% mortality

  • Post-treatment monitoring supported 100% successful eradication

Conclusions Desiccating or Freezing Conditions

  • No present techniques for totally eradicating zebra mussels from natural or source water habitats

  • KCl (Potash) application may be used successfully in small water bodies under the right conditions

  • Reduction in population densities may be achieved by control of water level

  • Effective control by natural mussel predators, disease organisms, and bacterial toxins will require further research and development

  • More effective density regulation technologies may be developed for open waters in the future

  • Time is on our side

PREVENTION Desiccating or Freezing Conditions

  • The most effective control methodology is PREVENTION

  • Assess vectors and threats for introduction of zebra/quagga mussels to a water body

  • Develop and execute plans to prevent introductions

    • Monitoring programs

    • Educate the public – encourage public cooperation

    • Post warning signs at boat launches

    • Eliminate all unattended boat launching sites

    • Inspect all boats launched, particularly those from states harboring zebra/quagga mussel infestations

    • Provide boat cleaning/mussel removal facilities at or near launch sites

    • Monitor/control bait sales preventing introduction of bait from mussel-infested waters

    • Review control plans developed for other water bodies

    • Develop an effective rapid response plan