This document discusses the threat of invasive zebra mussels spreading to Texas water bodies like Lake Conroe. Zebra mussels were first found in Texas in 2009 and can damage infrastructure, outcompete native species, and result in high mitigation costs. The document proposes actions like public education campaigns, monitoring, and researching control measures to prevent the spread of zebra mussels to Lake Conroe. Water chemistry factors that influence zebra mussel populations are also summarized.

1. Initial Information Gathering / Action
Plan for Lake Conroe Preparedness
July 21, 2010

2.  On April 3, 2009, the first adult zebra mussel
in Texas waters was confirmed living in Lake
Texoma. Invasive zebra mussels were also
found in a stream that feeds into Lake Lavon.
Experts fear they could eventually spread
throughout the Red and Trinity River systems
as well as much of Texas.
Texas Invasives.org

3.  The zebra mussel (Dreissena polymorpha) and
quagga mussel (Dreissena rostriformis
bugensis),collectively referred to as Dreissenids
are among the most devastating aquatic
nuisance species to invade North American
fresh waters
Western Regional Panel (WRP) for the Aquatic Nuisance Species Task
Force (ANSTF)

4.  Are the only freshwater mussels that attach to surfaces
 Can colonize the insides of pipelines and restrict the flow of
water
 Can damage boat hulls, plug water systems used in boat
motors
 Can result in costly mitigation expenses
 Can cause declines in populations of fish, birds and native
mussel species

5. View of exposed zebra mussels at a Kansas reservoir after a lake drawdown.
(Photo: Jason Goeckler, KS Department of Wildlife & Parks)

8.  January 28, 2010 TPW Commission Meeting
◦ Brian Van Zee discusses Zebra Mussels
 Transcript
http://www.tpwd.state.tx.us/business/feedback/meeti
ngs/2010/0128/transcripts/public_hearing/index.pht
ml
 Audio
http://www.tpwd.state.tx.us/business/feedback/meeti
ngs/2010/0128/agenda/

9.  Zebra Mussels in Texas: Assessment of
relative risks to fishery resources,
recommendations for action, and
expectations for the future
TPWD – Inland Fisheries Division, Heart of the Hills Fisheries Science Center
http://texasinvasives.org/resources/publications/TPWD_ZebraMussels_in_Te
xas.pdf

10.  July 19, 2010 Palms Marina Owner reported
Zebra Mussels on a Dry-Docked, NOT-
SEAWORTHY vessel that arrived from Lake
Texoma
 July 21, 2010 SJRA inspected and quarantined
the vessel

17.  Dreissenid mussel densities throughout the
West could vary widely depending on water
chemistry, food availability, and breeding
population
 Chemistry
◦ Calcium
◦ Temperature
◦ PH
◦ Other
Western Regional Panel on Aquatic Nuisance Species

18.  North American zebra mussel populations require
10 mg Ca2+/l to initiate shell growth and 25mg
Ca2+/l to maintain shell growth.
 Large populations of zebra mussels are not
expected where calcium levels are less than 25
mg/l (Hincks and Mackie).
 Cohen and Weinstein (2001) found little evidence
that zebra mussels can become established at
ambient calcium concentrations below about
20mg/l.
It should be noted that calcium may be elevated near concrete
structures (Cohen and Weinstein 2001).

19.  Dreissenids can tolerate a wide range of water
temperatures from roughly 32F to 86F (Ohio Sea
Grant 1997).
 Spawning will not generally occur at temperatures
below about 12C (Claudi and Mackie 1994).
 There is evidence, however, that quagga mussels in
deep waters of the Great Lakes are capable of
spawning at temperatures near 5C (Roe and
MacIsaac 1997) and 9C (Claxton and Mackie 1998)

20.  Larval development is inhibited at pH of 7.4
 Optimal larval survival occurs at a pH of 8.4
 Higher rates of adult survival occur at a pH of
7.0-7.5
 Optimal adult growth occurs at pH 7.4-8.0
(Benson and Raikow 2007)

21. VARIABLES HIGH MODERATE LOW VERY LOW
Dissolved Oxygen 8 – 10 6–8 4–6 <4
(ppm)
Water 18/64 – 16/61 – 18/64 9/48 – 25/77 <8/46
Temperature (C/F) 25/77 25/77 – 28/82 28/82 –30/86 >30/86
Total Hardness 90 – >125 45 – 90 25 – 45 <25
(mg CaCO3/l)
Calcium (ppm) 25 – 125 20 – 25 9 – 20 <9
pH 7.5 – 8.7 7.2 – 7.5 6.5 – 7.2 <6.5
8.7 – 9.0 >9.0
Salinity (ppt) 0–1 1–4 4 – 10 10 – 35
Conductivity 83 – >110 37 – 82 22 – 36 >22
(m Siemens)
Turbidity (secchi 40 – 200 20 – 40 10 – 20 <10
disk cm) 200 – 250 >250
Water Velocity 0.1 – 1.0 .09 – 0.1 .075 - .09 <.075
(m/sec) 1.0 – 1.25 1.25 – 1.5 >1.5
From European & North American Sources C.O’Neill, NY Sea Grant,
Mar 96

22.  Spawn 1-2 times/season
 Spawn from 54° to 80° F
 Become stressed at 86o F, die within a few
weeks.
 Die within 5 hours at 90o F.
 Grow @ 3mm/mo w/ @ 1 cm per year.
 Filter 1 liter of water per day.
Everett Laney, US Army Corp of Engineers, Tulsa

23. They like warm water!
Some spawning in water over 89o F for 2-3 months.
Surviving in water over 90o F for several weeks.
Can grow 1.19-1.25mm/week = 1cm in @ 2 months.
Everett Laney, US Army Corp of Engineers, Tulsa

24.  Adopt TPWD “Recommendations for Action” as
Initial SJRA Action Plan
◦ Direct control efforts toward Prevention
 Public Awareness (partner w/ LCA and others)
 Monitoring
 Law Enforcement
◦ Evaluate potential control or containment measures
 Inform L.C. Event Sponsors of the dangers and
precautions that must be taken prior to
launching
◦ Aquapalooza
◦ TTBC

25.  Public Awareness Campaign
◦ Partner w/ TPWD in:
 Community Outreach Efforts
 Posters
 Fliers
 Other
 Portland Sampling Efforts
 Law Enforcement Efforts

26.  Research
◦ Potential Control or Containment Measures
◦ Investigate Potential Surface-Water Intake Structure
& Spillway- Gate Modifications
 Coatings?
 Other
◦ N.T.M.W.D. Project (Alan Plummer & Associates)

27.  100th. Meridian Initiative
◦ http://www.100thmeridian.org/
 Aquatic Nuisance Species Task Force
◦ http://www.anstaskforce.gov/default.php
 Western Regional Panel on Aquatic Nuisance Species (Have
Developed A Detailed Action Plan)
◦ http://www.fws.gov/answest/aboutus.htm
 TEXASINVASIVES.ORG
 N.T.M.W.D. Contact – Mike Rickman 972-442-5405
 Army Corp Expert - Everett Laney, Tulsa Office 918-669-7411
 Alan Plummer & Associates Contact – Chuck Tracey, Ft. Worth office