Austin Watershed Protection Stocks More Grass Carp in Lake Austin to Help Manage Hydrilla

Austin Watershed Protection released an additional 7,091 sterile grass carp into Lake Austin on October 29 to help manage hydrilla, a non-native aquatic plant. The grass carp were released near Jessica Hollis Park, Walsh Boat Ramp, and Bull Creek where there is the most hydrilla.

Grass carp are an environmentally friendly, lake-wide, management tool because they prefer to eat hydrilla over other plants. The goal is to reduce dense hydrilla growth while keeping enough aquatic plants to support a healthy lake.

Texas Parks and Wildlife conducted a survey of vegetation in Lake Austin in mid-September, estimating 575 acres of hydrilla. Hydrilla coverage has remained stable since June, with some changes in where it is growing. 

Watershed Protection has developed a new predictive model using 15 years of Lake Austin data to guide grass carp stocking decisions. This model will help compare stocking options over time and under different lake conditions. The model is currently indicating that 7,091 grass carp should set us on a path to see a reduction in the extent of hydrilla. After each vegetation survey, the City will check conditions against the model’s predictions and adjust stocking plans as needed.

Residents and visitors can take the following steps to help prevent the spread of non-native species, like hydrilla: 

• Reduce or avoid the use of fertilizers in your landscape, especially if you live in areas that drain to Lake Austin; 

• Clean, drain, and dry your boat, trailer, and gear before and after use;  

• Avoid swimming and boating through dense patches of underwater vegetation; 

• If manually removing hydrilla from your shoreline, be sure plants are properly disposed of or composted. 

More information about hydrilla management in Lake Austin is available on the Lake Austin web page.

About Austin Watershed Protection

Austin Watershed Protection protects lives, property, and the environment of our community by reducing the impact of flooding, erosion, and water pollution. Visit AustinTexas.gov/Watershed to learn more.