They’re called zebra mussels, and Brian Van Zee, Texas Parks and Wildlife’s regional director of Inland Fisheries, said the black- and white-striped, filter-feeding menaces have been in Texas waters since 2009.
They’re members of Dreissena polymorpha, declared an “invasive species” under the National Invasive Species Act of 1996.
Texas Parks and Wildlife, the U.S. Geological Survey and various other agencies have kept a close eye on the invaders, which have gotten as close to the Tyler area in lakes Texoma and Ray Roberts, as well as more recent discoveries of trace amounts of zebra mussel DNA in the waters of lakes Lewisville, Bridgeport and Bob Sandlin.
Van Zee was quick to add, however, that the presence of this DNA more likely indicates the transfer of a boat between lakes than a mussel colony.
Growing up to only about 1.5 inches by adulthood, zebra mussels appear harmless. But appearances can deceive.
These mussels have a high proliferation rate, with one female producing up to 1 million eggs per year. This, combined with their filtration rate of about one liter of water per day, can lead to devastating ecological, economic and recreational consequences.
On the economic side, Van Zee described the mussels’ effect as “detrimental, particularly to municipalities.”
They can contaminate municipal water supplies, clog water infrastructure and wear out pumps, he said.
All things considered, invasions of zebra mussels have been known to cost millions of dollars in control and repair expenses.
On the recreational side, zebra mussels can attach themselves to the hulls of boats and clog their intake systems, damaging or even disabling the boat.
Also, with such a high reproduction rate, they also have a high death rate, and have been known to cover entire beaches with their shells, filling the air with their stench, Van Zee said.
The mussels’ spread has accelerated recently with good boating weather, as they prefer to live in warm, shallow water (6 to 30 feet deep).
Texas Parks and Wildlife asks that once boats are removed from the water, boaters clean them of mud and vegetation, drain them of water, and let them dry, ideally for a week. Alternately, a thorough drain and pressure wash will do the trick, but only if the water is heated to at least 140 degrees.