The signs of an encroaching menace can be found scattered under shoreline rocks, on the hulls of boats and along dam walls where the water meets the concrete. Small in size but carrying massive consequences, zebra mussels have invaded waterways across the nation and, as of last summer, have made their way into the waters of Lake Ray Roberts.
“As of right now, there’s really no practical cure for the problem. They basically have marched their way south from the Great Lakes area and westward,” said Chris True, superintendent of Ray Roberts Lake State Park. “They’re a bad thing, for sure. We need to do what we can to try and slow their spread.”
What Started the Influx of Zebra Mussels
Originally hailing from the waters of Russia, zebra mussels made their way into the United States in the 1980s. They were first discovered in Lake Texoma in 2009, according to the Texas Parks and Wildlife Department. Zebra mussel DNA was confirmed in Lake Ray Roberts in July of last year and, according to True, they are beginning to colonize the region.
“In the past year we’ve found some adults and certainly the juveniles in the water, but right now you have to kind of go out and hunt underneath rocks,” said True. “This spring, if it’s anything like other lakes where they initially come into, is when we’ll really see an explosion in their population.”
True speculates that while the invaders are scarce now, by this time next year “pretty much any rock you go out and turn over, you’re going to see zebra mussels.”
The Impact of These Small Invaders
While adult zebra mussels measure only 3.5 to 4 cm. in length, due to their quick reproduction, they pose a threat to native ecosystems. They are able to out-compete other filter feeders in the environment, which affects the larger fish species that feed on them.
They also clear water of algae and other microscopic organisms, allowing more sunlight to penetrate the depths. Eventually, zebra mussels can lead to an overall reduction in sport fish like bass and crappie.
Zebra mussels are also problematic to boat mechanics and water intake systems, as their hard shells can cover and clog anything submerged in the water.
True said that the mussels’ razor-sharp shells will also pose a problem for the park’s swim beaches.
“Periodically you’ll have a die-off of those adults and their shells are extremely sharp,” True said. “Our concerns are obviously our swim-beach areas and then places where people are getting in the water. I’m sure we’ll be recommending that you swim only in swim shoes or some type of footing and be extremely careful. So far we haven’t gotten to that point yet going into the season, but we are concerned.”
How to Slow the Spread of Invasive Species
Zebra mussel removal is highly labor-intensive and expensive, True said. The best defense against the invaders is slowing their spread by completely draining the water out of any vessel submerged in the lake before moving it to another body of water.
“We’re actively trying to educate the public through our Clean, Drain and Dry program,” said True. “Basically anything that can hold water has to be drained and dried before you leave the area. We’re really trying to slow their spread.”
Other Park Invaders
Slowing the spread is the best defense park officials have against invasive species, said Resource Specialist Bryan Daniels. While zebra mussels may be the most costly invader, they are not the only unwanted species plaguing the area.
The park also has issues with invasive vegetation, such as Privet and Japanese Honeysuckle. Privet shades out native plant species, while Japanese Honeysuckle entangles itself in trees, choking them in the process. Both plant species propagate well and can quickly replace the vegetation normally found in the park.
Eastern Redcedar is another problematic plant with an extensive root system capable of draining the water out of the soil before native trees and shrubs can get to it.
Daniels said that manual removal of invasive plant species is the most effective way of controlling them. Park staff members cut down stands of Privet and Japanese Honeysuckle, then apply an herbicide to ensure the plants cannot grow back.
“In the Honeysuckle, we are seeing progress. The Privet, because it is so good at reproducing, it’s an ongoing battle and we need more time and help basically to remove it,” said Daniels. “It’s very time-consuming and very manually intensive.”
Daniels said invasive plant species are usually spread by birds feeding on the seeds then dropping their remains in new areas. Both Privet and Japanese Honeysuckle began as ornamental plants, found commonly in residential landscaping.
Feral hog populations are also common in the park. Daniels estimates that around 200 hogs roam Isle du Bois and the Greenbelt.
“We have a lot of them. It’s primarily land destruction that they do through rooting. The disturbance allows other non-native invasive weeds and plants to come in our prairies, which are largely native,” he said. “It is a problem just because the number that we have at the park is more than we would like. We’ll never be able to get rid of all of them.”
Preservation Is the Top Concern for Park Officials
That is the common problem with all invasive species, said True. They out-compete native species at such a rapid rate that controlling their spread requires a lot of manpower.
“A lot of these species are invaders from other areas of the world and some from other areas of the country. We are actively trying to manage them, but manpower becomes an issue,” said True. “It’s very time-consuming, but it’s important to try to keep our resources what they should be or historically were.”
Daniels agreed, saying that while the problem is difficult to deal with, it’s important to try to maintain the park’s natural habitat.
“There’s never going to be a permanent solution, there’s only getting ahead of the problem,” Daniels explained. “It would take a lot of people and a lot of time to get ahead of the invasive species, so right now it’s just trying to keep it at bay, where it’s at, trying to stop the spread of it.
“I’m trying to contain it where it is so we can keep what we have everywhere else.”
This article originally appeared in the Pilot Point Post-Signal.
Heather Michelle Tipton 