Texas Freshwater: Lake Austin Grass Carp Response - Texas Fish & Game - October 2012 Texas Freshwater: Lake Austin Grass Carp Response - October 2012 By Matt Williams
Editor’s Note: In the Sept. 2012 issue of Texas Fish & Game, Freshwater Editor Matt Williams wrote about an apparent plan by the City of Austin to stock as many as 15,000 triploid grass carp into Lake Austin to combat the growth of hydrilla in the 1,600 acre lake. These fish may only be introduced to a public lake with the blessing of TPWD through the issuance of permits.
Not everyone is happy about the grass carp release. Area bass fishermen are especially concerned, mainly over fears that the carp will totally eradicate what many consider to be a key link in a chain of ingredients that has made Lake Austin one of the "best little big bass lakes" in the state.
Williams believes the worries about Lake Austin’s habitat are justified, and he let the department know it with a letter (also published last month) to inland fisheries director, Gary Saul. Dave Terre, chief of fisheries management and research, answered promptly with the following response:
Triploid grass carp have been stocked in Lake Austin for the past nine years. We’ve been successful in keeping a serious hydrilla problem in check, while still maintaining other species of aquatic vegetation to benefit anglers. Every decision we make to stock grass carp into Lake Austin considers the preservation of non-hydrilla vegetation and this great fishery. Since these stockings began in 2003, thirteen ShareLunkers have been caught in Lake Austin and abundant stands of aquatic plants remain. We view this stocking strategy as a success and plan to continue the effort into the future.
Hydrilla can provide good fish habitat and can result in better fishing for anglers. Unfortunately, hydrilla grows rapidly and can cause problems for many reservoir users. In some cases, we can just leave it alone if its growth is not creating problems for the fishery, boat access, or operations of the lake.
Anglers must realize that fishing is just one of many uses of our public reservoirs and most were not built to provide fishing as a primary use. However, rest assured that enhancing fishing quality remains TPWD’s top priority anytime vegetation control becomes necessary.
In the past, excessive hydrilla growth in Lake Austin has created significant and expensive problems for the Lower Colorado River Authority (LCRA), including repairs and lost power generation. It also caused flooding into homes and restricted lake access to property owners and boaters.
TPWD represented the anglers and engaged itself in a collaborative process with the City of Austin, the LCRA, and interested user groups to explore treatment options. Chemical and mechanical removal options were not considered feasible. The City of Austin did not want to use herbicides because Lake Austin is a drinking water supply lake. Mechanical controls were expensive and might spread hydrilla through plant fragmentation (cutting). The only feasible and affordable option was triploid grass carp in conjunction with periodic drawdowns.
TPWD was comfortable with this decision because Eurasian watermifoil, which was abundant in the lake, was not a preferred food item for grass carp. TPWD knew it could tightly control the number of fish that would be stocked through our permit process. For the past nine years, hydrilla growth has been under control, Eurasian watermilfoil remains a dominant habitat type, and fishing is great.
We understand and share the fears that some anglers have regarding the use of triploid grass carp and their potential for causing damage (or sometimes elimination) of non-targeted plants. Unfortunately, this could occur despite our efforts to balance the number of grass carp needed to control hydrilla, while still maintaining viable stands of other plants to provide habitat.
While still not a perfect or exact science, we’ve shortened native plant recovery time by stocking less grass carp and by planting native aquatic vegetation. Far less grass carp were stocked in Lake Conroe this last go-around, as compared to the legislatively-mandated stockings that occurred in the 1980’s. We also consider our past native planting projects a success because they helped create 1,500 acres of vegetated habitat necessary for the production of most of Lake Conroe’s ShareLunkers.
Recent vegetation plantings since the last introduction of grass carp (late 2000’s) are responding quicker now than before, based on our surveys. Recently, TPWD began working with partners to reduce excess numbers of grass carp in some lakes though organized fishing tournaments. Our efforts to remove excess grass carp, albeit limited in scale, are designed to get a faster turnaround time on rebuilding native aquatic plant communities. Lake Austin has not seen the challenges faced at Lake Conroe. We think the presence of Eurasian watermilfoil, cooler water temperatures, and the fact that Lake Austin is a constant water level reservoir, have led to more stable amounts of vegetative habitat under this grass carp stocking plan.
We understand the value and importance of aquatic vegetation habitat, especially for largemouth bass. Where hydrilla needs to be controlled, we do it carefully using a well thought out management strategy that considers all reservoir users. Our goal is always to provide quality fishing and retain vegetation habitat. Where hydrilla is not in conflict (or a threat) to other uses, we generally leave it alone. We invite all anglers to become involved in our reservoir habitat improvement projects. We have numerous on-going projects statewide.
