●Lake Ouachita Vegetation Control ● ●
Hydrilla once established in Lake Ouachita will 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 Lake Ouachita, hydrilla will effectively displaces beneficial native vegetation such as wild-celery (Vallisneria americana)and coontail (Ceratophyllum demersum). (Bates and Smith 1994)
Hydrilla was first identified in Lake Ouachita in 1999 during creel surveys. Lake Ouachita is a 44,000 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.
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.
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 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 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.
Hydrilla, a submersed freshwater herb, does more on Lake Ouachita
than fouling boat props. It also blocked marinas
and choked up swimming area, raising concerns that its
growing impact on recreation could upset the economy of the area.
The plant has grown explosively in Lake Ouachita 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 Richard 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.
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.
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.
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 it 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.
It likely got into Lake 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 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
(ANS), an
intergovernmental organization formed to prevent and control aquatic
nuisance species.
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