Lady Bird Lake vegetation at risk after ‘mass migration’ of carp

Asian carp. (KXAN File Photo)
Asian carp. (KXAN File Photo)

AUSTIN (KXAN) – On a steamy summer morning, professional bass fishing guide Ray Tomasits rigged up 10 fishing rods and carefully placed them across the front of his powerboat before pushing off the bank of Lady Bird Lake.

With a KXAN crew in tow, Tomasits stood at the bow, maneuvered the trolling motor with one foot and spoke, all while deftly zipping sidearm casts beneath low-hanging branches and lobbing lures just inches from the bank.

Tomasits was searching for bass, but there’s another fish in the lake that has him and other Central Texas anglers concerned.

State and local officials released tens of thousands of Asian grass carp into Lake Austin to combat overgrown vegetation in recent years. They came. They ate. They conquered. Then they kept swimming.

“After seeing what they did to Lake Austin, I’m a little worried,” Tomasits said. “They’ve completely decimated any aquatic vegetation that was in Lake Austin. Anglers now are pretty cynical about the whole deal, and they call [Lake Austin] a mud pit.”

The invasive grass carp, which are imported sterile and grow to over 50 pounds, have now moved downstream in droves into Lady Bird Lake. Marcos De Jesus, a fisheries supervisor with the Texas Parks and Wildlife Department, called it a “mass migration” through the floodgates of Tom Miller Dam, which links Lake Austin to Lady Bird Lake.

Lake Austin was recognized nationally as a top bass fishing destination as recently as 2014. Since that year, vegetation coverage has dropped to zero, and the lake is no longer ranked, according to Texas Parks and Wildlife Department studies and Bassmaster rankings.

While De Jesus is hopeful Lady Bird Lake will remain an excellent fishing spot, many local fishermen aren’t as optimistic.

The big release

The whole problem started with the onset of exceptional drought from 2009 through 2011. As lakes Travis and Buchanan — Central Texas’ largest reservoirs — began drying up, the Lower Colorado River Authority reduced the flow downstream through a series of Central Texas dams. LCRA controls water flow and hydroelectric power from the lakes and the Colorado River down to the Gulf Coast.

Low water flow, higher-than-normal temperatures and lack of floods led to the aggressive expansion of underwater aquatic vegetation, especially hydrilla in Lake Austin. Hydrilla, a non-native weed, can grow from as deep as 20 or 30 feet to the surface.

The plants created a veritable underwater jungle. It was great for fishing and the food chain, providing habitat and hunting grounds for all manner of fish, from minnows and shad to perch and largemouth bass. But the dense mats of hydrilla also brought a new set of problems. They were dangerous to swimmers and boaters, could increase flooding and foul up power plant machinery.

De Jesus said the release of the carp was necessary to maintain safe and usable lakes. TPWD and state experts were aware the carp could move downstream at some point, he said.

“This is something I’m not trying to downplay,” De Jesus said. “It’s serious. We knew it could happen, so right now it’s more of a control situation to see how we can revert things to where it was.”

Drag the slider to see the progression of the problem.

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Ray Tomasits fishing on Lady Bird Lake. (KXAN Photo)
Ray Tomasits fishing on Lady Bird Lake. (KXAN Photo)

A solution with a problem

Typically TPWD maintained conservative stocking rates for the sterile grass carp. The moderate stocking levels were based on scientific literature that outlined a carp-per-acre formula. Since 2002, officials worked to maintain a fine balance between safe plant levels and fish habitat, said Brent Bellinger, a senior aquatic scientist with the Austin Watershed Protection Department.

But around 2011, moderate stocking wasn’t keeping up with the “aggressive expansion” of hydrilla, said Bellinger, who was not an employee of the city at the time. By 2012, the City of Austin, TPWD, LCRA and a local group called the “Friends of Lake Austin” agreed to cooperate on a significant increase in grass carp stocking.

The stakeholders “all purchased grass carp as part of a combined management plan approved by TPWD,” said LCRA spokesperson Clara Tuma, in a prepared statement.

Bellinger said they released somewhere between 30,000 and 50,000 carp between 2002 and 2013.

Indeed, local fisherman, including Tomasits, said the hydrilla was getting excessive in Lake Austin. But the grass carp countermeasure was also overdone.

Kevin Olivier, founder of Austin Carp Angler, said he’s concerned about the health of Lady Bird Lake after seeing what happened in Lake Austin.

“When it was really bad in Lake Austin, [grass carp] were coming up out of the water and picking leaves off of trees,” Olivier said. “Fishermen were saying they saw them ‘porpoising’ out of the water and grabbing leaves.”

Now the “grassers,” as many anglers call them, present an existential threat to Austin’s common carp and smallmouth buffalo fishing in Lady Bird Lake. Buffalo and common carp, which are less known as a sport fish but have an avid following, are also vegetarians.

“That presents a problem because there are only so many weeds in Lady Bird,” Olivier said.

Bellinger said the city is aware the carp have moved into Lady Bird Lake, but he said he doesn’t expect a similar situation to what happened in Lake Austin. Lady Bird Lake has never supported much aquatic vegetation, he said. During the recent drought years, an aquatic plant called fanwort expanded beyond normal ranges around the Barton Creek inlet in Lady Bird Lake. Like hydrilla in Lake Austin, the fanwort provided great habitat for fish.

Historic 2015 floods on Halloween and Memorial Day scoured the bottom of Lady Bird Lake and tore out nearly all vegetation. So it wasn’t the grass carp that decimated plant life in Lady Bird Lake, De Jesus said.

The issue now, said De Jesus, is that the grass carp could hinder plant regrowth.

The city is actively replanting vegetation in Lady Bird Lake. The grass carp will naturally die off or swim down through Longhorn Dam and into the Colorado River, Bellinger said.

In September of 2016, TPWD revoked the need for a permit to keep grass carp caught in Lake Austin. According to TWPD’s website, there is no permit for taking grass carp on Lady Bird Lake, either, if the head or guts are removed immediately. A valid fishing license is still required to fish the lakes.

In the meantime, anglers are hopeful the situation doesn’t turn worse for bass, common carp and smallmouth buffalo fishing in Lady Bird Lake.

On KXAN’s June morning fishing trip with Tomasits, he struggled at first to land a largemouth bass. A severe storm the night before had turned the lake the color of mocha and filled it with acres of floating debris. Extremely tough fishing conditions, he said.

But after we passed beneath an old train trestle, Tomasits flipped a chartreuse plastic frog just an inch from the bank. A bass struck the floating lure, and after a short fight, the fish flopped awkwardly on the deck of the boat. Tomasits smiled with relief.

“What me and a lot of people hope for is the ecosystem to come back into balance,” he said. “It’s just going to take time…just hopefully not too much.”

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