A small freshwater mollusk called the zebra mussel (Dreissena polymorpha) has invaded fresh waters across Canada and North America. Boaters are carelessly spreading this destructive pest in bilges and bait wells of trailered boats. Boating in Canada has been complicated, since even small boats without special bottom paint will grow these mollusks within a few months. They have spread to the Great Lakes, the St. Lawrence River and many freshwater lakes and canals, changing the very face of our aquatic ecology.
They first appeared in Canada in 1988 in Lake St. Clair, a small lake connecting Lake Huron and Lake Erie in the Great Lakes. It is assumed the zebra mussels were discharged in the ballast water from a ship from a freshwater European port. (About 160 invasive species have been imported by cargo ships, most causing environmental and economic problems.)
Zebra mussels can survive up to 5 days out of water. They live only in fresh water and attach themselves to any underwater surface. They are about the size of a fingernail but can grow up to 5 cm. long. They need flowing fresh water to thrive so are not as much of a problem in quiet lakes and bays. A female is able to lay up to one million eggs during a single breeding season! The only natural control is a species of diving duck.
Zebra mussels spread downstream during their free-swimming larval stage. Dispersal upstream and into inland rivers and lakes occurs with human activity: larvae are dumped from livewells and older ones attach themselves to boats. Trailered boats are to blame for spreading the mussels throughout the fresh water lakes and rivers in the Great Lakes basin once they were introduced there (believed around 1988).
Cooling water left in an engine cooling system when a boat is not in use does not seem to support their growth. They do not attach themselves to hulls protected with anti fouling paint. Colonies of mussels can clog water intakes on boats in use however.
Zebra mussels often fasten themselves in clusters to the shells of native mussels, preventing them from breathing, feeding and moving, so they die. Clams have virtually disappeared from western Lake Erie! Colonies of zebra mussels in Lake Erie have reached astounding densities of 70,000 per square meter according to estimates. Lake Erie is estimated to be filtered completely each week. Because of this, zebra mussels have high concentrations of toxins -- which are passed on to any waterfowl that feed on them. Water clarity has increased sixfold and light reaching the bottom has caused increases in bottom plants.
Zebra mussels clog water intake pipes and turn docks and pilings into surfaces that can tear your skin off. Clogged water supply pipes have cost many millions of dollars to repair.
They filter algae from the water, turning it clear. Scuba diving in the Great Lakes area has become a growing sport because you can now see in the water. Unfortunately, the absence of microscopic aquatic plant and animal life will cause many species to disappear as the ecosystem changes radically.
Hot water will kill zebra mussels (only useful for a very small bilge!). Chlorine will also kill them, but is very toxic to marine life. Potassium, bromine, ozone and ultraviolet light are less toxic alternais are difficult to apply under water. A novel experiment was reported at the Sixth International Zebra Mussel and other Aquatic Nuisance Species Conference in March 1996,
Researchers at Purdue University have discovered that radio waves will kill zebra mussels. Their experiments exposed them to low-energy radio waves in fish tanks, which killed the zebra mussels in 40 days. It appeared the radio frequency caused them to lose the calcium they need to survive. Other organisms in the tanks, such as other freshwater mussels and crabs were significantly less harmed and fish were not harmed at all. This is not very practical for a lake but could be used around water intakes.
"...included "Penaten" cream, a product normally used by parents of newborns. This product, which has a significant zinc component, not only reduced mussel settlement but also prevented diaper rash on all of the boats tested! "
Some say 'get out the butter and garlic!' as there must be some other silver lining in this pest!
Source: Great Lakes United, www.glu.org
Quagga mussels are closely related to zebra mussels. The nonnative organisms have infested the Colorado River system and could easily spread throughout the Pacific Northwest on trailer boats.
Quagga mussels are very small but breed quickly and adhere to practically any surface. They threaten native fish by consuming food and smothering other species. As with zebra mussels, they can clog pipes and water intakes, and cause damage to hydroelectric dams and irrigation systems. The mussels are hardy, capable of surviving out of water for a month and tolerant of a wide range of temperatures and water conditions.
The organisms spread by riding on boats and trailers that have been in an infested lake or river. Pressure-washing boats and trailers with scalding water destroys the mussels.
Native to the Caspian Sea, zebra and quagga mussels entered the Great Lakes in the mid-1980s in ship ballast water. As of 2009, they have spread to 20 states and two Canadian provinces. Boat owners need to take responsibility for their vessels to keep these invasive species from spreading to other waterways.
Other invasive species: Round Gobie (fish), Rusty Crayfish, Rudd (fish), Eurasian Ruffe (fish). Report sightings to Invasiding Species Hotline (below).
One of the few places where an invasive plant, hydrilla, was stopped from spreading is Lake Manitou on Manitoulin Island, Ontario, between Lake Huron and North Channel. The lake was closed for three years, the waters treated and the invasive plant was stopped. It would have been deadly if it had spread to the Great Lakes. It was probably brought in on a boat transported from somewhere else.