The City of Austin is ramping up efforts to control the spread of hydrilla in Lake Austin, releasing nearly 2,800 sterile grass carp into the water earlier this month.
According to Austin Watershed Protection, 2,790 grass carp were stocked on May 1, primarily near Tom Miller Dam and Mansfield Dam—areas where the invasive plant is most concentrated.
Hydrilla, a fast-growing non-native aquatic plant, is now covering about 37% of Lake Austin, up from roughly 30% in September. A survey conducted by Texas Parks and Wildlife in mid-February estimated hydrilla growth across 592 acres of the lake.
City officials say the grass carp are being used as a natural management tool, as the fish prefer to feed on hydrilla over other aquatic vegetation. The latest stocking is intended to increase the population from about five to eight fish per acre of hydrilla.
The goal, officials say, is to slow the plant’s rapid growth and reduce its density without harming the lake’s overall ecosystem.
Recent environmental factors—including a warmer-than-usual winter and increased nutrient levels in the water—have contributed to the plant’s expansion.
While hydrilla can provide benefits such as fish habitat and improved water quality, it can also grow thick enough to interfere with recreation and disrupt the lake’s ecological balance.
City leaders emphasize that managing hydrilla is a long-term process, and it could take several growing seasons before the impact of the additional grass carp becomes noticeable.
In the meantime, residents and visitors are being asked to help prevent the spread of invasive species by taking a few precautions:
- Limit or avoid fertilizer use, particularly in areas that drain into Lake Austin
- Clean, drain, and dry boats, trailers, and equipment before and after use
- Avoid boating or swimming through dense vegetation
- Properly dispose of or compost any hydrilla removed from shorelines
Additional information about hydrilla management is available through Austin Watershed Protection.
