State park leaders are asking everyone heading out to the lake for Memorial Day weekend to take extra precautions and help stop the spread of zebra mussels.
On Friday members of Texas Parks and Wildlife met at Lake Ray Roberts in Pilot Point where the invasive species was located last summer and has already infested the lake.
"One adult zebra mussel can spawn up to a million eggs in a year," said Regional Director Brian Van Zee.
At this point the mussels have been found in both Lake Ray Roberts and Lake Texoma and were just recently discovered in areas of the Trinity River in Denton County.
"It's not a good sign," Van Zee said. "It means the numbers are increasing."
Zebra mussels are dangerous for a number of reasons, Texas Parks and Wildlife biologist Todd Robinson said. Because they're not native to the area, they pose a ecological risk of eating the food sources of other lake life.
But the physical damage may be the bigger problem. The mussels, which are very sharp and easily stepped on by beachgoers, latch onto things such as boats, rocks and important infrastructure.
"Any means of water conveyance -- pumps, pipes -- they get in and attach to the insides of these structures," Robinson said. "Once they're there, there's really nothing that you can do about it."
The North Texas Municipal Water District is currently working on projects to extend its pipeline by 46 miles because of zebra mussel damage to existing pipes coming from Lake Texoma.
"Lake Texoma makes up 28 percent of our total raw water supply that we use," NTMWD spokeswoman Denise Hickey said.
The district has also had to fix damage on some of its water intake structures, a costly problem that will roll down.
"The impact to the end user is an increase in their end water rate," Hickey said.
Zebra mussels aren't native to the United States but likely came here after attaching to a ship that traveled into the Great Lakes, Robinson said.
It's how they keep moving -- by attaching to boats.
State officials are urging all boaters to thoroughly clean off their boats, empty out any and all water on board and dry off a boat before moving it into a different body of water.
Robinson says that will prevent the spread and infestations of any other bodies of water.
Failure to do so, he adds, can be costly. In Texas, it's a misdemeanor to transport an invasive species. It is punishable by up to a fine of $2,000 and 180 days in jail.