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Lake Ouachita vegetation
is being addressed by the U.S. Army Corps of Engineers, Arkansas Game and Fish Commission,
and the Lake Ouachita Association to control Hydrilla
and Eurasian watermilfoil.
Bill Barnes, owner of
Mountain Harbor Marina, and representing the
Lake Ouachita Association
(a group of
lake resort and marina owners), says the vegetation has gotten so bad that tourists are
starting to avoid coming to Ouachita.
The 15 Member
Lake Ouachita Citizen Focus Committee engaged its first effort to
address the Lake Ouachita aquatic weeds in November 2001, when it conducted
a workshop to discuss the perceived problems and potential solutions
available.
AGFC district
fisheries biologist Stuart Wooldridge points to the increasing amount of vegetation as
leading to an increase in the lakes pickerel population,
a
predator fish that competes directly with largemouth bass.
The goal of the project is to contain and reduce the vegetation, not eradication,
since the presence of aquatic vegetation in moderate amounts is beneficial to the lake's
fishery, Wooldridge said.
Satellite imagery
by the U.S. Army Corps of Engineers shows the lake contains 10,000 acres of vegetation,
according to Richard Stokes, Lake Ouachita project manager. The goal of the
project is to reduce the coverage by 2,000 acres. We will concentrate on high recreational
use areas, such as swimming beaches, around marinas and popular boating areas. Areas of
the lake containing good fishery habitat will not be treated, Stokes added.
The C.O.E. is treating 13 areas with
Pakistani flies a tiny fly that resembles a gnat in size and hops along
the water surface rather than flying. The Corps of
Engineers will inoculate 13 selected areas of Lake Ouachita with
the fly , whose larvae feed exclusively on hydrilla. The Larvae of the fly
will kill the upper three feet of the plants. The Pakistani hydrilla
leaf-mining fly's larvae (hydrellia pakistanae) burrow into the leaves of
the plant. Each larva can destroy nine to 12 leaves during its feeding
cycle.
The flies will take several years to become noticeably effective.
Lake Ouachita Weed Identification

Hydrilla Verticellata Description:
Hydrilla Verticellata, commonly referred to as Hydrilla is a
very invasive submersed freshwater herb. It was originally sold
as an aquarium plant. It forms very dense strands growing from
the bottom of the water and sprawling across the surface.
Although it is an excellent source of food for waterfowl, it can
be a serious threat to freshwater habitats and a nuisance to
boaters.
Hydrilla reproduces by fragmentation. It does not form any
seeds. Hydrilla produces large strands of plants in just a few
months through its efficient use of low light levels and
available nutrients. Even small pieces stuck on boat propellers
or in bait pails contribute to the easy spread of Hydrilla to
other waterways.Hydrilla Verticellata
Identification:
Green, freshwater herb
Submersed plant with long slender stems
2 to 8 small, spear-like leaves per whorl spread across the
water
The leaf has a sawtooth edge and small spines on the underside
that are rough to the touch
Grows in as little as a few inches of water or in more than 30
feet of water
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Milfoil Description:
Eurasian Watermilfoil (Myriophyllum Spicatum) is native
to Europe, Asia and northern Africa. It was introduced to the
United States many years ago in the 1940's. Eurasian Milfoil is
an underwater plant and bears only a slight difference from US
native Milfoil. Because it is an attractive plant, it was once
commonly sold as an aquarium plant. The Eurasian Milfoil has
12-21 pairs of leaflets leaf and the native northern Milfoil
only has 7-11 pairs of leaflets
Milfoil grows best in fertile, inorganic sediments. It prefers
very active lake beds which receive nitrogen and
phosphorous-laden runoff. Because of the poor seed germination,
it reproduces by fragmentation. It produces fragments during the
summer after fruiting once or twice. The shoots get carried away
by currents or boaters. Because of its ability to spread
rapidly, it often blocks out sunlight for plants native to the
lakes. The dense groups can also block out larger fish,
therefore disrupting the predator-prey relationship. Many
waterways become congested due to these dense groups as well.
Milfoil Identification:
Reddish-brown plant stem that thickens below the water
and curves to lie parallel with the water surface
Submersed feathery leaves
Tiny 4 part flowers stick out 2 -4 inches above the water
The flowers can be four petaled or without any petals
The fruit is contained in a hard capsule with 4 seeds in it
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Coontail Description:
Coontail (Ceratophyllum demersum) is a free-floating
submersed plant without any roots. They are found all over the
world growing in sluggish water. Sometimes they are loosely
anchored in the mud. Coontail draws its nutrients from the water
directly rather than from sediment like most rooted aquatic
plants. It can survive in cool waters and low light. During the
winter months, it lives under the ice as an evergreen plant and
resumes rapid growth in the spring. Many people place coontails
in their ponds to give protection and shade for fish.
Coontail Identification:
Dark green forking leaves, up to 1 2 inches in length
arranged in whorls on the stem
Submersed plant without roots
Plants may be bushy or very long and sparse
Feathery leaves on the stem resemble a raccoons tail. The stems
can be 1 to 2 feet in length.
The leaf has small teeth on the midribs which make it rough to
the touch
It has very small flowers which are rarely seen |
Hydrilla was first identified in Lake
Ouachita in 1999 during creel surveys. Lake Ouachita is a 42,000 acre lake,
with an approximate hydrilla infestation size of 4,000 acres. Hydrilla has
been verified growing in waters of 24 feet with expected growth to be in the
30 - 35 foot level in the near future and due to light penetration
possibly to 40 feet.
The AGFC has stocked
10,000 grass carp in seven selected areas to contain the spread of new vegetation. Grass
carp feed on vegetation, preferring Hydrilla to the Eurasian watermilfoil.
Hydrilla Impact on Lake Ouachita in Arkansas.
Once established, hydrilla results in an array of ecosystem disruptions.
Changes often begin with its invasion of deep, dark waters where most plants
can not grow. Hydrilla grows aggressively and competitively, spreading
through shallower areas and forming thick mats in surface waters that block
sunlight penetration to native plants below. In the southeast, hydrilla
effectively displaces beneficial native vegetation
(Bates and Smith 1994) such as
wild-celery (Vallisneria americana) and
coontail (Ceratophyllum demersum).
Hydrilla has been shown to alter the physical and chemical
characteristics of lakes.
Colle
and Shireman (1980) found sportfish reduced in weight and size when
hydrilla occupied the majority of the water column, suggesting that foraging
efficiency was reduced as open water space and natural vegetation gradients
were lost. Stratification of the water column (Schmitz et al. 1993; Rizzo et
al. 1996), decreased oxygen levels (Pesacreta 1988), and fish kills (Rizzo
et al. 1996) have been documented. Changes in water chemistry may also be
implicated in zooplankton and phytoplankton declines (Schmitz and Osborne
1984; Schmitz et al. 1993).
Hydrilla seriously affects water flow and water use.
Infestations in the
Mobile Delta are reducing flow in small tidal streams and creating a
backwater habitat
(J. Zolcynski pers. comm. 1998). Its heavy growth commonly obstructs
boating, swimming and fishing in lakes and rivers and blocks the withdrawal
of water used for power generation and agricultural irrigation.
The Mobile Delta consists of approximately
20,323 acres of water just north of Mobile Bay. Second only to the
Mississippi River Delta in size, the Mobile Delta is an environmental
showplace that is 30 miles long and 12 miles wide. It covers more than
200,000 acres of swamps, river bottomlands and marshes. Congress named the
Mobile Delta a National Natural Landmark in 1974; fewer than 600 sites have
received that honor. It is formed by the confluence of the Alabama and
Tombigbee Rivers. The Mobile Delta is a complex network of tidally
influenced rivers, creeks, bays, lakes, wetlands, and bayous.
LAKE OUACHITA - Rick Stokes wraps
the shiny green stem of a hydrilla plant around his
finger, making several turns before it finally breaks.
The stem is elastic enough that it wraps around boat props like that,
Stokes explains, until it chokes off the motor.
Hydrilla, a submersed freshwater herb, did more this summer on Lake Ouachita
than becoming a common way of fouling boat props. It also blocked marinas
and choked up the Crystal Springs swimming area, raising concerns that its
growing impact on recreation could upset the economy of the area.
The plant has grown explosively in the 41,000-acre lake in the past three to
five years and is becoming as problematic as crabgrass - but it is
considerably more difficult, and more expensive, to control.
Experts have told the U.S. Army Corps of Engineers,
which manages Lake Ouachita, that hydrilla can never be eradicated once it
infiltrates a lake.
...
"Our primary concern is around the swimming areas, the boat ramps, the
marina areas and our recreation areas," says Stokes,
Lake Ouachita park manager for the Corps of Engineers.
"It's a lot worse on the west end of the lake, in the south fork of the
Ouachita River," he said.
On the west end of the lake, a number of boat owners are starting to
question why they're docked on Ouachita, if they can't get their boats out.
There is growing concern they will pull up and go elsewhere, which would
have a major economic impact on concessionaires and other businesses.
About 1,000 acres of the lake are affected by hydrilla. Stokes said
controlling the weed has become one of his top five
budget priorities, because of its aggressive nature.
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Native aquatic plants cover about 6,000 acres on the lake, but
Stokes said hydrilla will likely take over those
areas in three years.
"The more funding, the more area we'll look at. Within the budget right now,
60 acres is about what we can top out, as far as what we can spend on this,
because it's so expensive," he said.
Hydrilla cannot be controlled through drawdowns, like other underwater
weeds. It is rooted, and can survive a freeze. Drawdowns actually give it an
advantage over other native plants.
"The lake drops, you kill out the other stuff, and that gives this stuff
even greater opportunity to grow," Stokes said.
The native plants have been around for about 20 years.
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The Corps of Engineers has eradicated those plants,
where necessary, around boat docks and other areas if they posed a nuisance,
but those varieties didn't pose the threat of hydrilla, according to
Stokes.
Stokes said he is trying to set up special funding
for bio control measures, which could start as early as next spring but
would take a decade to be established as a major control.
"You don't have the capability of sitting and watching it. You have to
attack it. That's what's really got us concerned," he
said. There's a hitch: while it may be the right time to attack the weed,
the Corps of Engineer's budget was reduced this year and will be cut another
25 percent next year.
Stokes is scheduled next week visit Alabana's Lake Guntersville, which has
had hydrilla for 11 years, and observe its control measures.
"That lake is 60,000 acres. Right now they're having to treat 14,000 acres
for hydrilla.
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Contrary to what anglers believe, Stokes says
hydrilla is not good for fisheries because it can grow dense enough that
game fish can't get into it. The fish they feed on get inside the cover and
won't come out; the bigger fish can't get in it.
"The point I want to make to fishermen is that hydrilla is not beneficial to
fisheries. If anything, it's very contradictory to that. It gets so dense
they can't do anything," Stokes said.
...
We've had all this other stuff for 20-plus years that we've not had to
really worry with to a major degree," except around swimming areas and boat
ramps, Stokes said.
"But this stuff, this hydrilla, I'm telling you this stuff is bad stuff. It
will totally choke out almost the entire shoreline around this lake if not
controlled," he said.
"We've had a tremendous amount of complaints on this stuff," Stokes said.
"You cannot go through that stuff. I would let them show you an example, but
I don't want to be stuck," he said during a water
tour of the problem areas around Crystal Springs Recreation Area.
"You can see what we're dealing with on a small scale over just a three-year
period. You figure in 10 years what it's going to be like," Stokes said,
pointing out several small coves on the lake that are starting to get choked
with the plant.
"You can't eliminate it," Stokes said the experts have warned. "It's kind of
like crabgrass. You just don't get rid of it.
...
As the Corps of Engineers boat pulls into a cove
near Crystal Springs Resort, Stokes says "This is
what we're starting to find in a lot of areas around the lake." In the
sunlight, the top of the water has a shiny, mottled appearance, where the
tops of the weed are near the surface.
"The small coves are starting to get choked up with this hydrilla.
"If we don't do something with this cove, it will just continue filling all
the way back out. And really you can't do anything with it, then,"
he said.
...
While herbicides are the immediate fix - spray hydrilla today, and the weed
and all other plants are gone next week You're talking 10 years before
you see any major control" from bio measures, Stokes
says.
"So for the next 10 years, if I am able to deal with this by next year,
which I'm hoping to do, you're still looking 10 years out for the bio
controls to take over," he said.
Bio controls include the hydrilla Pakistani fly, which is actually a very
small gnat-like, leaf-mining fly.
When hydrilla surfaces, the fly lays its eggs on the plant, boring into the
stems and leaves, stressing the plant enough to where it's not as invasive.
There's also a weevil, but it cannot reach the plant when it is under the
surface, like the fly can. The weevil, unlike the fly, will migrate to other
aquatic plants, but none that exist in this area.
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It likely got into Ouachita by hitchhiking on a boat or trailer from another
lake, Stokes said.
That's another reason the Corps of Engineers is
concerned with people pulling their boat out of Ouachita - infesting other
areas. Some has already shown up on Lake DeGray.
"There's no silver bullet to this stuff. That's the sad thing about it,"
he said.
Tips for stopping the spread of hydrilla FROM STAFF REPORTS The U.S. Army
Corps of Engineers is urging recreational boaters to
not leave Lake Ouachita carrying hitchhikers of the aquatic variety.
The best way to stop the spread of hydrilla and other nuisance underwater
weeds to other lakes is to be vigilant about cleaning equipment, according
to the Aquatic Nuisance Species Task Force, an
intergovernmental organization formed to prevent and control aquatic
nuisance species.
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