Stop the Hitchhikers: Clean Your Gear

Contact: Jay Kilian, Maryland Department of Natural Resources, Resource Assessment Service | 410-260-8617

Zebra Mussel is an invasive species that has spread throughout much of North America as a hitchhiker attached to boat hulls, motors, and trailers. Although it is small, this species has big impacts on water quality, aquatic food webs, and industrial infrastructure in invaded areas. (Photo courtesy of Matthew Ashton, MD DNR)

ANNAPOLIS, MD (July 1, 2018) Summer is here and adventures await you on Chesapeake Bay and in Maryland’s beautiful streams, rivers, and lakes.  As you get out your waders, boats and fishing gear, keep in mind that your actions, or inaction, can cause irreversible damage to the very ecosystems you enjoy.  The gear that you use from your boots to your boat motor or trailer, and even your mask and snorkel, may harbor invasive species and contribute to their spread.  Zebra mussel, New Zealand mud snail, Didymo, and chytrid fungus are just a few of the harmful species that have been inadvertently spread throughout many regions of the U.S. by outdoor enthusiasts; including kayakers, canoeists, anglers, boaters, and divers.  Stopping the spread of these species in Maryland requires your vigilance!  With the summer of 2018 here, the Maryland Invasive Species Council has chosen “Clean your Gear” as the July 2018 Invader of the Month.

Recreational gear can become a vehicle on which invasive species can be carried from one water body to another.  For example, the Zebra mussel (Dreissena polymorpha) is an invasive mollusk native to Eurasia that was first introduced into the Great Lakes in 1986. Since then, this species has been introduced throughout much of North America, spread primarily by recreational boaters.  Zebra mussel has “hitchhiked” great distances attached to boat hulls, props, or motors, or hidden in live wells, coolers, and bait buckets.   Recreational boaters trailering their boats from one water body to the next can inadvertently spread zebra mussels and other “hitchhiking” organisms.  Invaded areas have suffered ecologically.  Zebra mussel has drastically altered aquatic food webs and has 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 of dollars annually to treat.  The control of zebra mussels and other aquatic hitchhikers cost us all a lot of money!

Zebra mussel was first discovered in Maryland in 2008 in the Lower Susquehanna River at Conowingo Dam.   Over the past ten years, it has become more abundant throughout the river from Conowingo Pool to the Susquehanna Flats near Havre de Grace.  It has also been found in the tidal, freshwater portions of the Sassafras, Gunpowder, and Middle rivers – areas that are popular boating destinations.  This species may invade other Maryland rivers, lakes, and reservoirs with the aid of boaters unaware of the issue. 

Zebra mussels, invasive aquatic plants, and other large organisms attached to boat hulls, props, or trailers are usually easy to detect and remove.  But, not all hitchhiking species are obvious.  Many are not easy to see, even if you are looking for them.  Microscopic algae, pathogens, or larvae can remain hidden in your recreational gear and can also be transferred from one water body to the next if you are not careful to thoroughly clean your gear between water bodies and outings.

New Zealand mud snail is one of the latest ‘aquatic hitchhikers’ to enter Maryland waters. These tiny snails (black specks on the sycamore leaf in photo) could be carried inadvertently from the Gunpowder Falls to other waters if preventive measures are not taken by anglers and other recreationists.

In 2017, the New Zealand mud snail (Potamopyrgus antipodarum), a small invader barely five millimeters in size, found its way to Maryland waters.  The site of this new invasion was the Gunpowder Falls downstream of Prettyboy Dam – a popular trout stream frequented by anglers from throughout the Mid-Atlantic region.   This snail was first introduced to the U.S. in Idaho in 1987.  It has since spread to ten other western states, two Canadian provinces, and the Great Lakes.  It first appeared in the Mid-Atlantic in 2013 in Spring Creek near State College, Pennsylvania – one of the more famous trout streams in the region.  New Zealand mud snail is a prolific species that reproduces asexually, each producing up to 100 clones in a single year. It can thrive in a variety of habitats including streams, rivers, ponds, lakes, and brackish water.   Mud snails can attain high densities with over 750,000 snails per square meter reported in some invaded waters.  Feeding on algae and other organic matter, this snail has the capacity to affect aquatic food webs and may compete with native snails and other invertebrates. Its potential impact to the Gunpowder Falls ecosystem is currently unknown.  What is known is that this invasive species could find its way to other Maryland waters on contaminated wading boots, fishing gear, or other recreational equipment if precautions are not taken.

New Zealand mud snail is not the only tiny invasive species that is a potential big threat to Maryland’s aquatic ecosystems.  Didymo (Didymosphenia geminata), commonly called “rock snot”, is a species of algae that has invaded several coldwater streams in Maryland over the past ten years (see the original July 2012 IOTM for details).  Chytrid fungus and ranavirus are infectious agents that have decimated populations of amphibians and reptiles in many parts of the world, including Maryland.  These tiny pathogens can also be spread on contaminated recreational gear.

Didymo, or ‘rock snot’ is one of many invasive species that can easily be carried into new waterways on recreational gear such as chest waders, canoes, or kayaks. It can form thick mats on stream bottoms, smothering habitats important to many native species. (Photo courtesy of Katherine Hanna, MD DNR)

Protection of our waters from invasive species requires an informed and vigilant community of anglers, boaters, canoeists, kayakers, divers, and other outdoor enthusiasts here in Maryland and the rest of the country. Your actions can make all the difference. 

You can help prevent the spread of invasive species by cleaning all of your recreational gear after each trip.  There are several ways to decontaminate your gear so that you do not move invasive species around.  To protect our waters, always:

  • Remove all vegetation, mud, and other debris from your gear
  • Drain all water from live wells, bilge, motors, canoes, and kayaks
  • Clean your gear with high pressure, hot water, 10% bleach solution, or other effective cleaning agent. Be sure to use bleach and other cleaning agents away from waterways to reduce potential harm to non-target animals.
  • Let your gear dry for at least 48 hours (preferably longer) between trips

And most importantly, spread this message to other Marylanders! Give them this information and tell them to pass it on!

For more information on cleaning your gear and other invasive species visit these links:

Originally posted as the Invader of the Month in July 2012.  Updated July 2018.

Cleaning your recreational gear is an easy and effective way to prevent the spread of invasive species. For example, removing your wading boots (pictured here) and spraying all exposed surfaces with a 10% bleach solution or other cleaning agent can kill hitchhiking species including Didymo, chytrid fungus, and ranavirus.