The Texas Parks and Wildlife Department says Medina Lake is now "fully infested" with zebra mussels. The invasive species was first spotted in February at Medina Lake, which is a little more than 40-miles west of San Antonio. Subsequent surveys last month found that the mollusks are reproducing at Medina Lake, prompting Parks and Wildlife to designate it as fully infested in a news release late last week. Zebra mussels put native fisheries at risk and can cause millions of dollars in damage to water pipes.