Boaters Beware!

Contact: Jay Kilian, Maryland Department of Natural Resources, Resource Assessment Service |

Invasive aquatic plants such as Hydrilla can easily become entangled in boat props and trailers. If not removed by informed boaters, these plants and other hitchhikers can be moved and introduced into new waters. Photo: Emily Johnstone, Ontario Federation.

ANNAPOLIS, MD (June 01, 2016) – The 2016 boating season is here and it is time for all boaters who enjoy Maryland waters to take an active role in protecting them from the scourge of invasive aquatic species. So as you prepare for your summer excursions, keep in mind that your actions, or inaction, can cause irreversible damage to the very ecosystems you enjoy. Your boat, outboard motor, trailer, and even the water in your live well or bait container can harbor invasive species — from entangled aquatic plants to microscopic larvae of invasive mussels — and if you're not careful, you could contribute to their spread. Stopping the spread of these harmful species will take the combined efforts of an informed boating community. With water temperatures rising and boat traffic increasing on our rivers, lakes, and Chesapeake Bay, the Maryland Invasive Species Council has chosen "Boaters Beware" as the June 2016 Invader of the Month.

Invasive aquatic plants, crustaceans, mollusks, and other animals are a growing threat to Maryland's streams, rivers, and lakes and to the tidal waters of Chesapeake Bay. The spread of these invasive species can cause severe damage to aquatic ecosystems, affect native wildlife, and reduce recreational opportunities such as fishing, boating, and swimming. Boats and trailers can serve as vehicles on which invasive species can be carried from one water body to another. Recreational boaters can inadvertently spread invasive "hitchhiking" organisms that become entangled on trailers, attached to boat motors, or concealed in live wells, compartments, or bilge areas.

Boating has been one of the main pathways responsible for the spread of the invasive zebra mussel (Dreissena polymorpha). This small, invasive mollusk, native to Eurasia, was first introduced into the Great Lakes in the mid-1980s. Since then, this species has been transported and introduced by recreational boaters throughout much of North America. Invaded areas have suffered ecologically. Zebra mussels have drastically altered aquatic food webs and have been linked to declines in commercially important fisheries. The economic impacts of zebra mussel invasions have been huge. Biofouling by zebra mussels of municipal and industrial water pipes and infrastructure require millions annually to treat.

Zebra Mussels are established and on the rise in the Lower Susquehanna River and Upper Chesapeake Bay in Maryland. Adult mussels (pictured here) attached to pipes, piers, and boats will be a costly nuisance to boaters, marinas, and local industries in the area. Photo Credit: John Gallagher, MD DNR Boating

Zebra mussels were first discovered in Maryland in the Lower Susquehanna River in 2008. Over the past seven years, these mussels have increased in abundance and are now regularly found attached to piers, pilings, and other hard surfaces in the Susquehanna and the Upper Chesapeake Bay near Havre de Grace. If the trend continues, this species will become an ever increasing nuisance to boat owners and marinas in the area. The threat looms large as zebra mussels may invade other Maryland rivers, lakes, and reservoirs with the aid of boaters unaware of the issue.

As with zebra mussels, recreational boaters are the key to stopping the spread of hydrilla and other invasive aquatic plants. Hydrilla (Hydrilla verticillata) is a prolific invasive species native to central Africa. First introduced in Florida in 1960 as an aquarium plant, hydrilla has since spread across much of the southeastern and Gulf Coast states. Hydrilla infestations can displace native vegetation, reduce fish habitat, and cause low oxygen concentrations in surrounding waters. Dense hydrilla mats often impede waterways reducing navigation, fishing, and swimming in infested areas. Hydrilla invasions have been costly. Florida, California, and many other states spend millions annually to control this invasive species.

Hydrilla has been established in the Potomac River since the early 1980s. However, this invader was only recently discovered, in 2013, in a portion of Deep Creek Lake in Garrett County, and in Lake Habeeb in Rocky Gap State Park in 2015. Concern over the potential ecological and economic impacts to Deep Creek Lake prompted a hydrilla treatment project initiated by the Maryland Department of Natural Resources in 2014. Using the herbicide fluridone, the treatment project has greatly reduced hydrilla growth and distribution in the lake to minimize ecological impacts and maintain the recreational attraction of this popular tourist destination.

Zebra mussels, hydrilla, and other large organisms attached to boat hauls, props, or trailers are usually easy to detect and remove. But, it is important to remember that not all hitchhiking species are easily detected by sight. Many are not easy to see, even if you are looking for them. Microscopic algae, pathogens, or larvae can remain hidden in your boat and other recreational gear and can also be transferred from one water body to the next if you are not careful.

Protection of our waters from invasive species requires a vigilant community of boaters here in Maryland. Your actions can make all the difference. You can help prevent the spread of invasive species by taking these steps after each trip. To protect our waters, always:

  • Remove all mussels, vegetation, organic matter, and mud from your boat hull, external drive unit, propeller, anchor, and trailer. Pay particular attention to material clinging to hubs, license plates, and taillights. Dispose of all material in the trash or away from Maryland waters.
  • Drain all water from live wells, bait buckets, bilge, compartments, and other areas that can hold water. Take this step before you leave the boat ramp or in an area where contaminated water will not enter other water bodies.
  • Clean your boat hull, trailer, and any other exposed surface. Spray all areas with a high-pressure washer* or use a mild bleach solution (13 oz. per gallon of water). Pay particular attention to anchors, lines and ropes, engine cooling systems, bilge areas, live wells, and trailer bunks and rollers. 
    *Power washers available at commercial self-service car washes are a great way to reduce the potential for invasive stowaways.
  • Or Dry your boat and trailer for at least two days between trips. Longer dry times are encouraged, especially if your boat has been used in infested areas.

And most importantly, spread the word to other boaters! Give them this information and tell them to pass it on!

For more information about other Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council or call the Maryland Department of Agriculture at 410-841-5920.

photos available electronically on request.

For more information on the Internet:Invasive and Exotic Species in Maryland, Maryland DNR.
Zebra Mussel – Invader of the Month, January 2015.
Video: Maryland DNR Fights Hydrilla Invasive Plant in Deep Creek Lake.