Hydrilla, a submerged aquatic invasive plant, could be making a comeback in Canyon Lake thanks to a mild winter and stable water levels since 2018.
Texas Parks and Wildlife Department (TPWD) Biologist Patrick Ireland, who works out of the Inland Fisheries Division in San Marcos, spent Monday out on the water looking for it.
“Our previous vegetation/habitat survey was performed in August of 2019,” he said in an email. “During that survey, very little vegetation was found on the lake. However, we have recently — this summer — been getting quite a few reports of hydrilla and other aquatic vegetation showing up in the lake.”
TPWD performs routine vegetation surveys on Canyon Lake every three or four years to keep tabs on the aquatic habitat, Ireland said. Historically vegetation in Canyon Lake is limited and fluctuates through the years.
But this week’s visit was geared toward finding areas of higher plant density and gathering enough data to get a good grasp on the number of aquatic plants like hydrilla and pondweed actually in the reservoir.
“The results from this survey will be used to help guide our process for management decisions when we work with our partners and the controlling authority,” he said.
“Once we process the data from today’s survey, we should have a very good idea of the current status of the hydrilla in the reservoir.” –TPWD Biologist Patrick Ireland
Ireland recorded the spatial location and extent of hydrilla in Canyon Lake. Data collection included finding and recording the location of both submerged and ‘topped-out’ hydrilla that’s reached the surface of the lake.
“To do this, we use sonar and visual observations as well as a vegetation rake to confirm what we are seeing underwater,” Ireland said. “All of this data is recorded in our field notes as well as a precision GPS system. Once we process the data from today’s survey, we should have a very good idea of the current status of the hydrilla in the reservoir.”
TPWD drafts updated reports for most of its water bodies every four years.
According to its website, overabundant vegetation can limit recreational access, restrict flow rates in canals and rivers, interfere with industrial water uses and harm fish and wildlife.
In recent decades, species such as hydrilla, water hyacinth and giant Salvinia have invaded many Texas waterways. They travel from one watershed to another by way of boat propellers, bilges and livewells.