Service technician Tim Ray was inspecting a boat that had just arrived from Wisconsin when he noticed clusters of mussels attached to the trim tabs and outdrive of the 27-foot power boat.

“There were probably a thousand or so of them,” Ray said. “They were hard to see, because the boat had not been washed and they had slime covering them. I picked one off and cleaned it up, saw stripes on it and figured it was a zebra mussel. I’d seen warnings about them, and figured I might see some one day.”

Ray looked up information on zebra mussels on the Internet and confirmed his suspicions. “I showed one to the service manager and said we needed to call someone.”

The service manager placed a call to Grayson County game warden Dale Moses, who inspected the boat with Texas Parks and Wildlife Department Inland Fisheries biologist Bruce Hysmith. The two positively identified the shellfish as zebra mussels.

The boat was immediately quarantined indoors with a tarpaulin beneath it to prevent any mussels from reaching the water.

Moses contacted the owner of the boat, who had recently moved to Texas, and informed him of the situation. The owner agreed to follow TPWD’s instructions for decontaminating the boat and was issued a warning citation for possession of a prohibited exotic species.

“Mr. Ray is to be commended for being aware of what zebra mussels are and for stopping the process of putting the boat into the water,” said Moses. “Most people in his position would probably not have noticed or cared enough to stop and identify them, and would have launched the boat.”

Zebra mussels are about 5/8-inch long and are named for the striped pattern of their shells, though the stripes may sometimes be absent. Native to the Black, Caspian and Azov seas of Asia, zebra mussels spread across Europe in the 18th and 19th centuries as canals were built. They were first discovered in North America in 1988 on the Great Lakes and have since spread to more than 20 states in the Mississippi River basin.

Zebra mussels have been reported to be one of the most important biological invasions into North America, and there has been tremendous effort to halt their spread to the Southern states.

Overland dispersal via boats being trailered from one body to another is known to have occurred. Under cool, humid conditions, zebra mussels can survive for several days out of water.

Zebra mussels are notorious for fouling the water supply pipes of power plants, water supply plants and industrial facilities. As many as 700,000 zebra mussels per square meter have been observed at a Michigan power plant. Such large concentrations of mussels restrict water flow, reducing intake. Zebra mussels on boats increase drag and can get into engine cooling systems and cause overheating. Zebra mussels attached to metal or concrete structures can cause corrosion and affect structural integrity. The mussels feed on the tiny organisms that form the base of the food chain for fish and may negatively impact a number of aquatic species.