How To Avoid Spreading Invasive Species

Consider these simple steps to help protect your waterways

Zebra Mussels

A well-kept boat is the joy of any proud boat owner. There is more to keeping a boat clean, though, than just soapy water and good old-fashioned elbow grease—especially lately. 

Grit and grime on your boat pale in comparison to an invasion of plants, fish and animals—collectively called aquatic invasive species—on your local waterways. Sea-going vessels, barges, recreational watercraft and even boat trailers are responsible for spreading them.

Aquatic invasive species are prolific breeders and quickly become established where they don’t belong. Each year, they cause billions of dollars in economic and ecological damage by clogging water intakes, causing fish kills, closing public beaches due to health concerns, endangering valuable food and gamefish species and impeding navigation. Once these invaders gain a foothold, it’s very difficult and expensive to get rid of them.

Also called exotic species, they first entered the Great Lakes in the ballast water of European cargo ships and spread from there. Some of the species are microscopic, while others appear to be nothing more than harmless weeds.

What does all that have to do with fishing and pleasure boating? More than you might think. Multiply the number of those boats by the miles traveled over land and water. The sum of that equation proves why steps are being taken to prevent the spread of these problematic species.

A growing number of states enforce strict boating laws against the transport or possession of exotic species. If caught, violators face hefty fines, impoundment of their boats and even jail time. Enforcement often begins at the launch ramp.

Boaters are on the front lines of helping prevent the spread of aquatic invasive species. Understanding what they are, how they spread and what you can do to prevent their spreading is worth the effort.




Meet The Suspects

Recreational boaters should be especially on the lookout for aquatic plants and mussels on the hit list. Those species can be unknowingly transported on trailers and boats.

In the plant category, the lead suspects are Hydrilla, Eurasian Watermilfoil, Giant Salvinia and Water Hyacinth.

Hydrilla and Milfoil were imported to the U.S. for use in aquariums in the 1950s. The species entered Florida’s inland waters after being discarded or planted in canals. Hydrilla is now in 28 states and spreading. Milfoil is more climate-tolerant and found nationwide. 

Hydrilla and milfoil are mainly introduced to new waters as fragments on recreational boats, their motors and trailers and in livewells. Colonization begins after the fragments are dislodged from a trailer, emptied from a livewell or pumped out of a bilge.

Stem pieces root in the bottom and develop into new colonies, commonly beginning near boat ramps. Once established, boat traffic continues to break and spread Hydrilla and Milfoil. Because of how fast it colonizes and spreads, the plants are difficult to control. Mechanical harvesting is mostly ineffective, leaving chemical herbicides as the only option for controlling it.

Giant Salvinia, a South American aquatic fern, imported as an aquarium plant, is now rapidly expanding in public waters. Plant coverage can double in size in about a week, and the thick mats deplete oxygen content and impede boating and fishing. A single acre can explode to more than 2,000 acres in just 12 weeks. To get that started all it takes are broken plant stems attached to a boat trailer. Giant Salvinia tops the list of problematic plants in Texas.

Water Hyacinth is a floating plant that forms dense rafts in the water. Look for large spikes of lavender-blue flowers, spongy, bulbous leaf stalks and large, rounded leaves. Hyacinth also has a high growth rate, doubling in size in as little as two weeks by sending off short runner stems that develop new plants. 

Outside of plants, Quagga and Zebra Mussel invasions have catastrophic impacts in the ecosystems they invade. They clog water intake structures, which greatly increase maintenance costs for water treatment and power plants. Recreational activities on lakes and rivers are adversely affected as mussels accumulate on docks, buoys, boat hulls, anchors and beaches can become heavily encrusted.

The shells of both mussel species are sharp and can cut people, which forces the wearing of shoes when walking along infested beaches or over rocks. Mussels adhering to boat hulls can increase drag, affect boat steering and clog engines, all of which can lead to overheating and engine malfunctions.

The mussels were introduced into the Great Lakes after cargo ships discharged ballast water containing them. Today, they are among the most dangerous of all exotic species, due to their microscopic size and the difficulty of identifying them.


Zebra Mussels

Zebra Mussels

What You Can Do

Clean, drain and dry. That is the simple procedure to help prevent the spread of aquatic invasive species. If possible, do the cleaning at the boat ramp. If not, a car wash will work.

  • CLEAN off visible aquatic plants, animals and mud from all equipment, including all gear that’s been exposed to the water, before    leaving the boat ramp. Cleaning removes visible large-bodied organisms attached to the boat. Rinsing with water removes            organisms, while hot water often kills them. Water at least 120°F is recommended; be sure to avoid contact with skin and check        manufacturers’ recommendations to ensure equipment can withstand high temperatures. If hot water is not available or may cause damage, rinse with tap water and then let it completely dry before heading out again to help prevent the spread of aquatic invasive species.
  • Rinse equipment and boat hulls, preferably with a high-pressure hose at the ramp or a car wash.
  • Rinse interior compartments of boats with low pressure hot water.
  • Flush motor with hot water for 2 minutes (or according to owner’s manual).
  • DRAIN motor, bilge, livewell and other water containing devices before leaving water access. Draining removes small and nearly invisible organisms, such as Zebra Mussel larvae (veligers), potentially entrained in water-containing devices.
  • DRY everything for at least five days OR wipe with a towel before reuse. Drying is necessary as many organisms can survive in standing water. 

There is even more you can do to keep the problem from spreading.  

  • DISPOSE of unwanted bait, fish parts and packing materials in the trash—do not dump them in the water or on land. When keeping live bait, drain the bait container and replenish it with spring or de-chlorinated tap water. Never dump live fish or other organisms from one water body into another.
  • Report new sightings. If you think you have found an invasive species, note its exact location and, if possible, take a photo. Report new sightings to the appropriate authorities.
  • Know the rules! Specimens are needed to confirm sightings, but some jurisdictions prohibit possession and transport of invasive aquatic plants and animals. Before collecting specimens, contact your local natural resource management agency for instructions. Unauthorized introduction of plants, fish or invertebrates into the wild is illegal in most states. Protect your property and our waters.

Know your state boating laws. A growing list of 20 states are among those prohibiting the transport of aquatic invasive species. Most laws are enforced by state fish and wildlife agencies, and you are responsible for knowing the rules. 


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