Take action against zebra mussels

Zebra mussels (Dreissena polymorpha) have spread throughout the Great Lakes and in waterways in 18 states and two provinces since they were accidentally introduced into Lakes Erie and St. Clair in the 1980s. In 1991, a second species, quagga mussels (Dreissena bugensis) , was discovered. Quagga mussels are similar to zebra mussels, but they survive in deeper, colder waters. They have been found in the St. Lawrence Seaway, Lake Ontario, Lake Erie, and Saginaw Bay in Lake Huron.

The zebra mussels' range will continue to expand naturally as flowing water carries their young veligers downstream. Commercial and recreational vessels and equipment also can spread zebra mussels when they move from infested waters to uninfested waters. Adult mussels may attach to hard surfaces, and veligers may be transported in water. Veligers are small-about the size of the period at the end of this sentence-and may be able to survive in any residual water. Zebra mussels spawn when the water temperature is between 57 degrees and 68 degrees Fahrenheit (14 degrees to 20 degrees Celsius). Young quagga mussels have been observed in water as cool as 46 degrees Fahrenheit (8 degrees Celsius).

Some inland lakes have already been colonized by zebra mussels because of man's activities. For example, White Star Quarry, a 15-acre, 90-foot-deep Ohio lake, is not connected to any other waterway and is not used by boaters. It is, however, used by divers and anglers; and now it, too, is colonized by zebra mussels.

Nearly anything that has been in zebra and quagga mussel infested waters may have the mussels on them. This list of potential carriers includes:

• plants and animals
• any water
• snorkeling and scuba gear

There are currently several states with laws that prohibit intentional introduction of non-native species such as the zebra mussel. Other states prohibit the possession of some plants and animals, and still other states have laws pending. Researchers must follow protocols approved by an interagency committee to impede the spread of mussels to uninfested waters.

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The first step in the prevention of zebra mussel spread is to develop an attitude of concern. Second, accept the fact that your activities are a potential means of transportation, and third, adhere to the recommendations in this publication and to those of your state natural resources agency. An interagency Great Lakes task force recommends the actions (listed below) be taken after using a boat or other equipment in zebra mussel-infested waters. Be advised that these recommendations are still being studied by researchers and resource managers; therefore, the recommendations may change.

The longer a boat remains in zebra mussel-infested waters, the more apt it is to be fouled by zebra mussels. Therefore, boats that are docked or moored are more likely to be fouled by mussels than boats that are launched and retrieved in a single day.

The most expensive type of destruction to your boat is probably motor damage. Veligers can cause this harm when they are taken into the cooling system, where they can attach, grow and block intake screens, internal passages, hoses, seacocks and strainers.

The best prevention against such damage is to use your boat. Try to run your boat twice a week at high speed for 10 to 15 minutes. The mussels can't attach when the water velocity exceeds 1.5 meters a second (about 3.5 mph or about 3 knots) and may be washed off at speeds exceeding two meters a second (about 4.5 mph or 4 knots). The high-speed running will also help flush any attached young mussels from inside the motor systems, and the heat generated past the water pump will kill any veligers that may have been drawn into the system.

For outdrives and inboard units, run the engine at operation temperature for one-half hour each week. Watch temperature gauges and record readings for each use; any increase in readings over the previous use warrants disassembly and inspection of the cooling system. Consider installing a high temperature alarm.

After returning to the dock, flush any veligers out of the lower unit's intake by running tap water through the system. (Never use a chlorine mixture in the engine cooling system.) Do this by having a hose fitting installed on the intake system or investigate current commercial "engine boot" systems that contain lower unit water and that recirculate the heated water through the engine. This flushing practice, however, won't prevent veligers from entering the intake screens while your boat is at the dock.

Mussels can also accumulate around propeller shafts and can cause increased wear and possible damage to drive shafts or shaft seals. Reduce the amount of time in the water by tipping the drive units up and out of water when at dock.

During pre-season maintenance, and frequently thereafter, inspect cooling systems, intake screens, lower unit steering and hydraulic controls, propellers and propeller shaft seals. Frequently inspect the rubber boot that surrounds the I/O unit at the hull, because mussel shells can tear the boot, resulting in water entering the hull. Check water pump impeller for damage from shell fragments if adults are found near the intake systems. At the end of the season, follow the pre-season guidelines and disassemble everything, including the parts between the seacock and the engine.

Maintain a good quality antifoulant paint on the hull and other accessories because such paint releases toxins. Most marine algae, slime growths and mussels-including zebra and quagga mussels-are sensitive to these chemicals and will not attach to them. Several types of antifoulant paints exist, including copper-based, tributyltin (TBT)-based, copolymer, vinyl/epoxy binder, resin binder and hard- and soft-film types.

Copper-based paints are used on fiberglass and wooden hulled boats and accessories (trim tabs, etc.). They are usually viable for one or two seasons. A primer may be necessary on some surfaces, and the old coating must be removed first. A primer coat is absolutely necessary before applying to aluminum, because the aluminum and copper react with each other (electrolytic action) and cause corrosion. (Most lower motor units are aluminum.)

Tributyltin (TBT)-based antifoulants are restricted by law because they are extremely toxic. Early forms of TBT antifoulant paints leached biocides into the water and contaminated and killed nontarget organisms. In 1988, a federal law restricted the use of TBT as an antifoulant.

Some states have approved use of newer "slow-release" TBT paints (bulk brush-on) for application only on the hulls of aluminum boats and vessels exceeding 82 feet in length. This treatment can last two to three seasons when properly applied. The person applying the paint is required to obtain a pesticide applicator's license, generally available through your state's agriculture agency, to purchase and apply this antifoulant. Some states and provinces, including Michigan and Ontario, have banned the use of TBT paints altogether. Check applicability and legality of use of these paints with the product's manufacturer, boat dealer or regulatory agency. Where legal, a TBT-based spray for use on outboards, I/O sterndrives, propellers and internal passages is available for over the counter purchase.

Copolymer coatings are best for high-speed boats because they are thinner and smoother than the others. They are also recommended for trailered or rack storage boats because they only react when immersed in water. Other coatings oxidize when exposed to air for as little as one week and become useless.

Vinyls, epoxies and resin coatings allow biocides to leach to the surface.

Soft-film types result in a soft residue remaining after the biocide is leached out and are well suited for boats that remain in the water.

Hard-film types can be sanded to restore effectiveness.

Consult your manufacturer or boat dealer to determine the type best suited for your hull and accessories. Applying paints to some accessories may cause a loss in performance. Apply spray inside passages as far as possible. Some units require an annual breakdown for lubrication of the drive shaft; this is an excellent opportunity to spray deep inside otherwise hidden water passages.

Never apply a new antifoulant over an existing coating of another type. Remove old paint and read container labels for compatibility.

Remember, it may take only a few viable adult zebra mussels or a minnow bucket containing microscopic veligers to start a new colony. Do your part to prevent the spread while protecting your boat and equipment, too!

• Remove any visible vegetation from items that were in the water, including boat, propeller, trailer and all equipment. (Zebra mussels readily attach to aquatic vegetation.)
• Flush engine cooling system, live wells and bilge with hot water. If hot water is not available, use tap water.
• Rinse any other areas that get wet, such as water collected in trailer frames, safety light compartments, boat's decking and the lower portion of motor cooling systems.
• Water hotter than 110 degrees Fahrenheit will kill veligers, and 140 degrees Fahrenheit will kill adults. If hot water is not available, it is still important to rinse your boat and equipment. Do not use salt and chlorine water mixtures as both mixtures are very toxic to other organisms and may also damage boat equipment. Therefore, neither is recommended now for use outdoors.
• Always air dry boat and other equipment for five days before using in uninfested waters. If boat and equipment are completely dry for two days, it may be safe to use in uninfested waters.
• Examine boat exterior for mussels if it has been docked in infested waters; if mussels are found or exterior is heavily fouled by algae, either clean fouled surfaces or leave boat out of the water for at least five days before entering uninfested waters.
• If your gear feels gritty, then young microscopic mussels may be attached. Any mussels scraped off should be bagged and discarded in the trash.
• Do not re-use bait if exposed to infested waters.