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April 21, 2009
A Tale of Two Lakes
Battle against invasive species needs YOU
KARNACK and BROOKELAND, Texas — Caddo Lake and Sam Rayburn Reservoir are about as different as two lakes can be, yet both face the same threat.
Guarded by ranks of moss-covered cypress trees and valued mostly for its scenic beauty, Caddo is the only natural lake in Texas, a place where wildlife and people alike find refuge, a place often described with words like "magical" and "mysterious."
A-buzz with boats, Sam Rayburn Reservoir was built by the U.S. Army Corps of Engineers (USACOE) in 1965. It’s the scene of hundreds of fishing tournaments each year, events that bring millions of dollars into the local economy. When one talks about Sam Rayburn, words like "busy" and "economic powerhouse" come to mind.
Yet Caddo and Sam Rayburn are exactly alike in one respect: They are both under attack from giant salvinia and are in danger of losing the very qualities that make them valuable.
Then there’s this: What’s happening at these lakes could soon-very soon-be happening at a lake near you.
"Boat trailers are serving as the primary vector of transmission for giant salvinia," said Craig Bonds, regional director for Texas Parks and Wildlife Department’s (TPWD) Inland Fisheries Division. "If giant salvinia establishes colonies near boat ramps at Sam Rayburn, many other reservoirs will be threatened by this plant due to the high frequency of boat trailers leaving the reservoir for destinations all over Texas and the United States."
A native of Brazil, giant salvinia (Salvinia molesta) is a floating, rootless fern that can double its population in less than a week. Two years ago, fewer than 100 acres of the Texas side of Caddo Lake were covered in giant salvinia, and water hyacinth was the bigger problem. Extensive chemical treatment on water hyacinth opened up the water, and giant salvinia expanded to more than 1,000 acres currently-and the prime growing season is just beginning. In addition to Caddo and Sam Rayburn, a dozen other lakes have been infested by the plant.
Left unchecked, giant salvinia can form mats up to three feet thick and prevent light from entering the water, stopping the growth of tiny organisms that form the base of the food chain. The water becomes acidic. Decomposing plants consume dissolved oxygen needed by fish and other aquatic life. This is most likely to occur in coves, creeks and backwater areas-the very places that are nursery habitat for juvenile fish. Boating, swimming and fishing can become impossible due to clogged waterways. Fish and waterfowl are displaced.
Giant salvinia has the potential to become nature’s weapon of mass destruction.
It may seem almost too obvious to mention, but how we deal with giant salvinia will determine our chances of success. And the devil is in the details.
The Caddo Experience
As the only lake in Texas not built by humans, Caddo is unique in that no governmental entity is in charge of taking care of the lake, according to Ken Shaw, chairman of the Cypress Valley Navigation District, which is charged by the Texas Legislature with the responsibility of maintaining the boat roads and channel markers on the lake.
"A number of organizations have been working to try to establish a plan of attack on giant salvinia," Shaw said. "It was decided the navigation district was the most logical choice to lead the effort."
The navigation district got funds from a number of sources, including the Texas legislature, for spraying the giant salvinia with approved herbicides, coordinated with TPWD aquatic vegetation control specialists and refurbished a spray boat from TPWD to use itself. Locals even built a two-mile barrier across the lake to prevent giant salvinia from blowing in from the Louisiana side, but the effort was not successful.
The absence of a controlling authority with responsibility for the lake has a profound implication: "If anything happens on Caddo, the local community has to get involved," Shaw explained. "Nothing can survive if giant salvinia takes a lake. Besides hunting and fishing, canoeing and camping, we have a lot of bed-and-breakfasts, motels and restaurants that depend on the natural beauty of this lake. If we want something done, we have to do it ourselves. There is no river authority to do it."
The Sam Rayburn Situation
The most likely source of the giant salvinia infesting Sam Rayburn Reservoir is Toledo Bend Reservoir, its neighbor to the east. Plants hitched rides on boat trailers traveling between the lakes.
"Since September 2008 we have had four separate introductions of giant salvinia on Sam Rayburn, and each one was found early and cleaned up and all plants removed," said Howard Elder, aquatic vegetation control specialist for TPWD. "It is important to note that in each of those cases, the introduction occurred within a few feet of a large warning sign placed by the USACOE and TPWD."
Those signs urge boaters to inspect and clean their boats of any plant material before leaving boat ramps, show pictures of giant salvinia and advertise the fact that transporting the plant is a class C misdemeanor punishable by a fine of up to $500 per plant.
During a recent bass fishing tournament on Sam Rayburn that attracted as many as 5,000 boats, Elder found ample evidence that the warnings on the signs are being ignored. "We found giant salvinia on trailers at ramps and in the water around those ramps," he said. "People brought giant salvinia to Sam Rayburn with them. Before the tournament we had giant salvinia contained. It may not be anymore. We will have to go to every boat ramp, walk the bank in every cove and pick up plants with dip nets to clean up these new infestations."
The Battle Continues
With giant salvinia spreading on both Caddo and Sam Rayburn, this spring promises to be a busy one for spray crews from TPWD and the Cypress Valley Navigation District. The stakes are high. "An economic impact survey of Caddo Lake anglers in a 12-month period during 2002 and 2003 estimated anglers spent more than $2 million, of which $1.6 million was spent locally," says TPWD’s Bonds. "Recent research conducted by Todd Driscoll, TPWD Inland Fisheries district biologist in Jasper, determined the recreational fishery at Sam Rayburn generated $31.8 million in direct angler expenditures and a total economic value of more than $45 million between November 2007 and October 2008. Giant salvinia poses a serious threat to both these valuable fisheries."
Crews will be making a concerted effort on Caddo in early May to treat all 1,000 acres currently infested. The herbicides alone for that will cost more than $75,000-and there is no guarantee of success. The Sabine River Authority will be spending more than $100,000 to fight giant salvinia on Toledo Bend-not to eradicate it, but to reduce the amount leaving that reservoir and infecting others.
In the case of all these lakes, the key to winning this battle can be found by looking into your mirror. "There is not enough money to fix the problem," Elder says flatly. "The only way we can lick this is if every individual takes responsibility every time he or she puts a boat into the water."
Points to Ponder
TPWD hunting and fishing programs are based on the concept of "user pays." Income from the sale of hunting and fishing licenses and taxes on sporting goods pay for wildlife and fisheries management, enhancement and protection. Yet most public reservoirs were built for purposes other than recreation.
The current situation with giant salvinia raises some troubling questions.
Whose responsibility is it, ultimately, to keep public waters free of invasive species? TPWD, the controlling authorities, water districts using the water or someone else?
Should everyone have to pay for cleaning up problems caused by those few who, knowingly or unknowingly, introduce invasive exotics into Texas waters?
At some point will treatment of infested water bodies become so much of a financial burden to controlling authorities that they will limit or eliminate public access in order to prevent future problems?
What You Can Do
- Inform yourself. Learn to identify invasive aquatic species.
- Remove all plant material from your boat, trailer and tow vehicle and place it in a trash receptacle BEFORE leaving a ramp area.
- Report sightings of suspected invasive species to TPWD (800-792-4263) and reservoir controlling authorities.
Texas Lakes Reporting Giant Salvinia
- Toledo Bend
- Sheldon Lake
- Lake Texana
- Lake Conroe
- Sam Rayburn
- B.A. Steinhagen
- Lake Pinkston*
- Center City Lake
- Brandy Branch*
- Lake Palestine*
- Cross Lake*
- Lake o’ the Pines*
- Lake Raven
* Infestation discovered early and successfully treated and removed
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