The City of Austin Watershed Protection Department sincerely appreciates concerns about the fishing resources of Lake Austin. City of Austin staff are coordinating directly with Texas Parks and Wildlife (TPWD) biologists to address concerns relating to the status of the fishery in Lake Austin. The City of Austin and TPWD are actively monitoring conditions in Lake Austin. Both the City of Austin and TPWD believe through combined natural recruitment, mortality of sterile grass carp, and enhancements that may be possible as a result of on-going City research efforts, the vegetation and bass fishery will recover.
Unfortunately, Lake Austin has experienced a fast decline in aquatic vegetation habitat. We were hoping for a more controlled decline, but other factors combined with the sterile triploid grass carp stocking led to the current low level of aquatic vegetation in the lake. Grass carp management has been studied for many years. The approach applied to Lake Austin was a replication of published scientific studies. For a decade we used a conservative incremental stocking rate which combined with a scientifically reported mortality rate avoided overstocking, allowing for continued fish habitat persistence. When extreme drought effects led to the rapid expansion of Hydrilla to more than 600 acres, the rate of fish stocking was increased to ensure the primary functionality of Lake Austin – water supply and flood protection – was not compromised. Our objective remains finding a medium where all lake use interests are met, including the anglers. The Lake Austin fishery is not doomed, and will recover.
For many years Lake Austin has provided excellent conditions to support a quality bass fishery with high trophy potential. Water temperatures, aquatic habitat, Florida largemouth bass stockings and responsible anglers are the reason for the success of this fishery. However, creating a trophy fishery takes more than just Hydrilla. It takes regulation, outreach, genetic stockings, habitat management, and the help of Mother Nature. The interests of anglers, boaters, skiers, swimmers, home owners, consumptive water rights, and operating infrastructure must be all considered equally.
While the explosion of Hydrilla temporarily amplified the great fishing at Lake Austin, it hindered other interests. For example, the last time Lake Austin had a heavy biomass of Hydrilla during a flood event the lake could not serve its purpose of flood control properly and millions of dollars in damage were caused to shoreline properties and the Tom Miller Dam. Excessive Hydrilla also causes safety concerns related to boating and swimming.
Aquatic vegetation challenges have existed in Lake Austin since the 1950’s, with Hydrilla being the most recent concern beginning in 2002. A partnership between TPWD, LCRA, City of Austin, and the Lake Austin home owners was developed to address this issue. The bass anglers at that time were asked to organize and delegate a representative to partner, but no one was
Control measures were put into effect to prevent potential detriment impacts caused by excessive Hydrilla growth. It was determined that Hydrilla was to be controlled through Triploid Grass Carp stocking to protect multiple user interests. TPWD is the agency responsible for permitting and regulating the stocking rates for Grass Carp in Lake Austin. As the Hydrilla aggressively expanded and impacted primary reservoir functionality and safety, we were forced to slowly increase stocking rates to 54 fish/acre of Hydrilla before we were able to see control. That resulted in the highest number of Grass Carp ever in Lake Austin. Chemical treatment for this type of coverage was not an option and mechanical harvesters could not keep up with growth and can exacerbate spread of Hydrilla.
The increased stocking rate did result in unintended significant fish habitat reduction in 2014. Additionally, untimely scouring, cool temperatures this past winter, continued drought, and altered hydrology have all resulted in a shift within this artificially created and highly regulated system to an alternative state dominated by planktonic algae rather than submersed vegetation. Throughout this summer and fall, short heavy rains have exacerbated the turbidity of Lake Austin through inputs from overland flow and tributaries. However, the current turbid condition of Lake Austin is temporary. There are still numerous propagating sources for native vegetation, protected by cages managed by the City of Austin. As the grass carp population is reduced through natural mortality, vegetation will re-colonize the lake and once again produce clear water conditions.
As published mortality rates of grass carp are estimated at 33% mortality per year, no organized grass carp harvesting effort is necessary or would be the most effective use of City resources. As the Grass Carp population shrinks and native vegetation and Milfoil expands, we should see the fishery recover. Should Hydrilla return in excess amounts in the future, it will be necessary to utilize grass carp again as a control agent. Thus, the stocking permit should not be eliminated especially given the difficult and lengthy process involved in procuring the permit initially.
Given our interest in the recreational as well as municipal use needs of Lake Austin, below is a brief list of efforts TPWD and the City of Austin are utilizing to understand the impacts of Grass Carp on this unique system and work towards system recovery.
We will continue to monitor aquatic vegetation habitat quarterly to see what changes occur.
We are studying trophic changes in the fishery food web as it relates to the changes in the plant community.
TPWD will continue to stock Florida largemouth bass as needed to keep the growth potential strong at the lake.
TPWD will continue to perform annual electrofishing surveys to monitor fish populations in relation to habitat changes.
We will continue to support efforts to establish native aquatic vegetation in the lake with the use of cages.
We will work closely with the water management authorities to advise on best management practices that would also consider the interests of our anglers.
We will keep the public informed of our progress on these and other topics.
We urge anglers to organize groups to represent their interests at meetings. The group can even become a chapter of Friends of Reservoirs (www.waterhabitatlife.org) and help us enhance fisheries habitat at Lake Austin and other area lakes. TPWD has done so with other groups on Canyon, Buchanan, LBJ, Inks, Granger, and Georgetown lakes. Please share this message with the anglers at Lake Austin.
Please contact Dr. Brent Bellinger (email), 512-974-2717) with the City of Austin if you would like to discuss this further. Thank you for sharing your concern, and for your support to protect Lake Austin.