Sterile fish to be released in Lake Austin, targeting invasive plant growth

AUSTIN (KXAN) — The City of Austin is releasing 350 sterile grass carp into Lake Austin this week to help control the spread of hydrilla, an invasive aquatic plant that’s begun growing again in parts of the lake.

Hydrilla is a fast-growing, non-native plant that can choke off waterways, lead to flooding and make the water difficult to navigate for boaters and swimmers. According to the city and Texas Parks and Wildlife Department, hydrilla is now covering about 5% of Lake Austin, particularly in coves and backwaters downstream of Loop 360.

The fish are being introduced to eat the hydrilla and help limit its spread. These fish are sterile and cannot reproduce.

If this sounds familiar, it’s because the city faced a major hydrilla problem more than a decade ago. First spotted in 1999, hydrilla covered about an eighth of the lake within just a few years. In 2003, the city and TPWD started adding the sterile grass carp, with more fish added over the years. That effort eventually worked, and the plant all but disappeared for years.

But now, the city says those older fish are nearing the end of their lifespan — and hydrilla is making a comeback. The older fish don’t eat as much of the plant.

The 350 fish are expected to supplement the small remaining population of older carp and provide targeted relief in areas where hydrilla is already reestablishing.