As grass carp gobbled up all the aquatic vegetation in Texas’ Lake Austin, they also obliterated the reservoir’s reputation as one of the nation’s top bass fisheries.
“When the grass was around 400 to 500 acres for a couple of years, the bass fishing really took off,” said John Ward, marketing director of the Texas Tournament Zone (TTZ). “The fish were fat and healthy. We had a great sunfish and crawfish population, and plenty of ambush spots for the big girls to grab them.
“Now sunfish and crawfish numbers are significantly down. You see more schools of bass chasing shad balls instead. The worst feeling is when you finally get a big girl, and it’s a 10-pound head with a 5-pound body. They just can’t eat like they used to.”
Understandably frustrated anglers blame mismanagement and/or the powerful influence of lakefront property owners who don’t like hydrilla. For example, one said that Texas Parks and Wildlife (TPW) “grossly overstocked this lake with grass carp.”
He continued, “In less than a year, we have seen complete devastation of this great fishery. The grass is 100 percent gone. Reeds that used to line the lake in places have been uprooted and chewed off at the stalks.”
But the reality is more complex and less malevolent. What happened was the inevitable result of an unavoidable set of circumstances involving weather, two exotic species, and reservoir management priorities.
“This trophy fishery was maintained along with grass carp stockings for many years,” said Texas biologist Marcos De Jesus.
“This extreme drought scenario has thrown a monkey wrench in our management efforts, but we are learning from this experience to avoid a similar outcome in the future.”
Managed by the Lower Colorado River Authority, Austin is a 1,599-acre riverine impoundment on the Colorado River. During normal times, cool discharges into the flow-through fishery combine with a sustained population of grass carp to keep hydrilla in check. Also, less problematic Eurasian watermilfoil thrives, serving as another control. But starting in 2011, drought diminished flow, allowing water to warm and igniting an unprecedented growth spurt in hydrilla. By spring 2013, hydrilla covered nearly a third of the reservoir.
If not kept in check, hydrilla can block flow, pushing water onto highly developed shorelines, De Jesus explained. Consequently, more dramatic control was required, and it could only be done with grass carp. Herbicides are not an option for Austin, which also serves as a municipal water supply.
A stocking of 9,000 carp in May 2013 supplemented 17,000 introduced in 2012, providing 55.5 fish per acre of hydrilla. And, as anglers watched in dismay, the fish quickly gobbled up all of the lake’s aquatic vegetation, except for shoreline plants protected by cages.
“Now we are in a situation where the carp are keeping everything at bay,” said the biologist. “Every time it’s been down to zero, though, it bounces back. We’re now looking at creating habitat (brushpiles) and doing some carp removal.
“Fishing always has been our priority,” he continued, pointing out that electrofishing revealed bass still are plentiful.
“But they’re now suspended in deep water, and people will have to transition to other fishing styles. We were all spoiled. We all loved that lake, and this change was not one that we wanted.”
Brushpiles will help, said Ward, who added that TTZ will help organizes anglers to assist. “But nothing can replace natural habitat. As long as you have 20,000-plus grass carp in a 1,600-acre lake, grass will not grow.
“It’s the aquatic vegetation and the healthy habitat it provides that brings out the potential for big bass in Lake Austin.”
(This article was published originally in B.A.S.S. Times.)