Anglers come from all over the world to fish Lake Fork, a 27,000-acre lake in east Texas with a reputation for producing monster fish. And in their quest to land a lunker, those fishermen also sustain the local economy. Which is why a new species in the lake has caused quite a bit of concern. And it’s not a species of fish, but a plant – an invasive floating fern called giant salvinia.

Giant salvinia was brought here from South America to be used in aquariums. It sucks up oxygen and pushes out native plants and fish. Despite the name, it’s actually small, about the size of a half dollar. It looks like a bright green circle with a crease down the middle.

“I mean it looks pretty harmless. But it’s by far the most troublesome invasive plant that we have and it really doesn’t have any ecological benefit, and you can’t fish it,” says Kevin Storey. Part of his job with the Texas Department of Parks and Wildlife it to monitor the lake. And right now, that’s a tough assignment.

Under the right circumstances, a salvinia infestation can double in size in just a week. It spreads by hanging onto boat trailers and motors. After invading lakes further east, it appeared on Lake Fork in November of 2015. Pesticides eliminated it in one spot, but it showed up in another part of the lake two years later.

“We’d think well we’ve got it under control, and it would pop up in another part of the cove. You get excited like ‘We’ve got it,’ and no you haven’t. It’s still there. And that is kind of draining,” Storey says.

It’s draining, and worrisome for some people. Lake Fork is known for big fish. Big bass in particular. The biggest largemouth bass ever caught in Texas was pulled out of Lake Fork in 1992.

The lake sits on land that was once hardwood forest and cow pastures. The grass and trees that remain underwater create a labyrinth of hiding spots for bass to grow. When the weather’s good, there’s a tournament almost every weekend.

“Once fishing season starts, people come form all over. Gas stations, grocery stores, everybody – we all rely on them guys coming her to go fish. If they quit fishing here, there’s nobody down here to spend money,” says Rick Scharninghausen, who owns and operates Lockhart Lures, a lure-making business on Lake Fork.

Scharninghausen started coming down from Wisconsin to fish Lake Fork in the 90s. He liked it so much, he decided to stay.

The walls of his one-room lure shop are lined with whatever you might need to land the big one. It’s the kind of business you find all around Lake Fork, along with fishing guides, marinas, mechanics and RV parks. They support a community where mailboxes are shaped like bass, and high school fishing teams get as much space in the paper as varsity basketball and football. But if the giant salvinia gets out of control, some parts of the lake could be un-fishable, according to Kevin Storey with the TPWD.

“Is it going to get to the stage where it’s everywhere, and, I’m sorry, in the back of coves it’s just going to be prohibitive to do any thing with it? And I, I just…I hate to think that that might eventually happen,” Storey says.

This isn’t the first time the local economy has stared down a threat like this though.

“I’ve seen it go through a lot of different things that people thought were going to be the lake’s end,” says James Caldemeyer, a pro angler on the Fishing League Worldwide tour and a Lake Fork fishing guide.

Caldemeyer has been fishing at Lake Fork since 1993, when the lake was producing even bigger fish than it does today. But that changed after 1999.

“Everybody thought the lake was done then when all the fish were dying,” he says.

A disease called largemouth bass virus decimated the lake’s marquee species. No one knew what caused it, and no one knew if the lake would be fishable again.

“It was kind of a ghostly feeling for those for us who have homes here to see this monster kill that was going on. It was really just a disheartening thing,” says Carolyn West, president of the Lake Fork Sportsman’s Association. The lake bounced back from the bass virus, and the association has worked to preserve it ever since. West says fighting the salvinia is just another part of that.

“We are all disappointed that it’s here but we will spring back from it,” West says. “And we know that businesses here can thrive if the lake thrives. We must get through this and we must help with it and we must go on to a healthier lake.”

Like West, Caldemeyer thinks if the lake could survive largemouth bass virus, it can surely survive salvinia. The prospect weighs heavily on Storey from Parks and Wildlife. The department keeps a close watch for more outbreaks, educates boaters, and is even experimenting with weevils that might eat the salvinia. But from the cab of his Ford F-250, he points out where the latest infestation has temporarily closed down a boat ramp on the lake’s southern tip.

“The major problem was back in here,” Storey says. “And it was all around that pier, and just kind of strung all along the shore. It basically had taken over the entire surface of the water where you really couldn’t fish it.”

Boat ramps like this one are the front line in preventing salvinia from spreading. If boaters regularly enter Lake Fork with salvinia they picked up elsewhere, it will spread even more, crowding out fish in the process. And whether that can be stopped will determine the health of a lake, an economy, and a community.

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