Grass Carp Ate All the Plants in Lake Austin. Now the City Wants Them Gone.

Sep 9, 2016

Standing next to Lake Austin, watching the wake of passing motorboat lick the shoreline, you likely wouldn’t think there was anything amiss. But just below the water’s surface many of the creatures that call the reservoir home are struggling for survival.  


“It’s loss of habitat, it’s loss off food, it’s loss of a lot of things” says Kevin Olivier with the group Austin Carp Angler.

Anglers, like Olivier, report that fish are getting skinny and sickly. Environmental studies show that vegetation has disappeared. Mortality has increased among some species.

Austin Carp Angler members (left to right) Kevin Olivier, August Wells and Keith Thompson.
Credit Jorge Sanhueza-Lyon / KUT

The reason? In 2011 the City of Austin started stocking large numbers of sterilized grass carp in the lake.

A video of the project posted online illustrates how Austin officials hoped the fish would fight a massive spread of the hydrilla plant.

Between 2011 and 2013 over 30,000 carp were pumped into Lake Austin. The fish ate the hydrilla, then started in on the other plants.

“We’ve had reports from bass anglers where carp were actually coming out of the water and picking leaves off trees” says Olivier.

"We’ve been hearing rumors that the bow fisherman are itching to get out there which can be a very effective method also for removal."

Anglers say the city put too many grass carp in the lake, starving out other species, though City of Austin scientist Dr. Brent Bellinger says that “depends on what you were trying to accomplish.”

He says the hydrilla plant can damage vital infrastructure, so the goal was to remove as much of it as possible to protect the Tom Miller Dam. Reports from 2011 also focused on how the plant was a nuisance to boaters and swimmers. From that standpoint, Bellinger says, the grass carp program was a success. Though, it did have some unfortunate consequences.

“Now, we’re taking the next step to help the system bounce back and recover,” says Bellinger. “We’re going to start removing triploid grass carp by one of the most effective [ways], which is angling.”

To put it another way, anglers are now allowed, even encouraged, to kill the grass carp that were introduced.

“We’ve been hearing rumors that the bow fisherman are itching to get out there which can be a very effective method also for removal,” say Bellinger.

Carp anglers, like Olivier, are generally in support of the new policy, though some worry it could create collateral damage.

“We need to be sure that people know that grass carp are the problem. Not common carp, not small mouth buffalo [fish] which are commonly mistaken as carp,” says Olivier. “One being the problem, one being just an unfortunate victim of the situation.”

Added to that worry is the fear that recent flooding has already pushed large numbers of grass carp downstream into Lady Bird Lake, where they might further disrupt the ecosystem.

“I’ve been fishing Lady Bird Lake for 15 years, and 15 years ago you didn’t see a grass carp,” says Keith Thompson, another fisherman with Austin Carp Angler. During a carp fishing competition on the Lady Bird Lake last February, he says, one team caught around 15 grass carp.

“They caught no [other kind of] carp,” says Thompson. “Just grass carp.”

Brent Bellinger says the city is working on outreach to educate people on the new fishing policy, and is monitoring the waters of Lady Bird Lake to see how many grass carp have moved downstream from Lake Austin.