Zebra mussels are continuing to spread through Texas lakes.
Texas Parks and Wildlife said Thursday that both Granger Lake and Lake Marble Falls are infested with the invasive species. The mussels have infested 19 lakes in Texas since their first appearance in Lake Texoma in 2009.
It's the second time this year the Lower Colorado River Authority has found thriving populations of the invasive mollusks in the Highland Lakes – the chain of manmade lakes that serve as a reservoir for Austin and much of Central Texas. LCRA found zebra mussels upstream in Lake LBJ in July, and the water authority expects them to spread farther upstream to Inks Lake and Lake Buchanan.
In Central Texas, the mussels have infested lakes Austin, Belton, Canyon, Georgetown, Lady Bird, LBJ, Pflugerville, Stillhouse Hollow and Travis – as well as Granger and Marble Falls. Biologists have also found larval mussels in Central Texas at lakes Dunlap, Placid and Walter E. Long, also known as Decker Lake.
The spread hasn't impacted new Texas rivers as of late, however, according to Monica McGarrity, a senior scientist with Texas Parks and Wildlife.
"Although it's saddening every time we find zebra mussels in a new lake or confirm that a lake is fully infested as we have with Marble Falls and Granger, it is still encouraging that zebra mussels have not been moved into any new river basins since 2017," she said in the department's announcement.
The mussels are often spread by boaters who unsuspectingly transfer the mussels themselves or water containing their larvae to lakes. TPWD urges boaters to thoroughly clean, drain and dry boats after docking.
Correction: A previous version of this story said the zebra mussel spread hasn't impacted Texas rivers as of late. The spread hasn't impacted new rivers.