Carp release in Lake Austin raises concern among local fisherman

AUSTIN (KXAN) -- A controversial plan to release grass carp in Lake Austin to fight hydrilla is drawing backlash from local fishermen.

On July 14, the City of Austin announced plans to release 350 sterile grass carp in the lake to help control the spread of hydrilla. Hydrilla is an invasive species that can be dangerous for swimmers and boaters, choking off waterways and making navigation difficult.

Grass carp eat hydrilla as their primary food source.

"What studies have shown is that as long as there is hydrilla present, they will kind of focus on that resource, allowing other plants to persist and thrive," said Dr. Brent Bellinger, conservation program supervisor with the city's Watershed Protection Department.

"By taking this kind of very scaled-down, measured approach, and also trying to get ahead of it, we're hoping to avoid some of the calamities of the past," Dr. Bellinger said.

More than a decade ago, a similar project to clear hydrilla led to devastation. A KXAN Investigation found that between 2011 and 2013, the City of Austin released 32,000 grass carp into Lake Austin in an effort to combat hydrilla.

Underwater vegetation suffered as a result. "If the hydrilla is absent, they will turn to other native vegetation," Dr. Bellinger said.

Fisherman against carp

"When you take all the grass out of a lake, everything kind of follows," said Carson Conklin with ATX Fishing. The Austin-native has fished on the lake for years. He now leads fishing tours. He said Lake Austin is one of his primary stops, with some best bass fishing in the country.

Without grass, Conklin said, small fish don't have food or habitats. Without the smaller fish, larger fish like Bass have nothing to eat, and fishermen have nothing to fish.

"Fishing a lake with grass is certainly more productive and more enjoyable," Conklin said.

While the previous project focused on the part of the lake west of Pennybacker Bridge, the new release will occur to the east of the bridge. The number of fish released is obviously much smaller, as is the amount of hydrilla they're aiming to remove.

"Austin is regarded as a very popular bass fishery. And so the absence of all vegetation is also not desirable," Dr. Bellinger said. He hopes the lower number of fish will ensure that only the hydrilla is targeted.

"That grass will get so thick that it's it will be hard to navigate some areas of the lake," Conklin said. "I think there's better ways to trim the grass down than grass carp. I think grass carp is a quick solution."

Other solutions include machines that act like underwater lawnmowers. However, hydrilla can survive mowing due to how it spreads. Hydrilla survives through fragmentation, where it breaks apart and replants elsewhere.

In 2017, following the initial release of carp, many carp traveled downstream to Lady Bird Lake. Dr. Bellinger expects the new crop will remain in Lake Austin, barring a major flooding event.