Stopping The Spread

Consider all bilge water to be contaminated.

Floats or hull should be drained where water will evaporate, and not flow into a nearby water body or wet drainage.

Stopping the Spread

Public Awareness

As the public becomes more aware of the invasive species problem, it will be up to us to convince regulators and local communities that we in the seaplane community are not only aware of the situation, but that we use good procedures to prevent transport of invasives in our normal flying. Having a procedures checklist on board to show interested parties may be useful in educating the public about our efforts. Inevitably, we will be called upon to explain why we should not be restricted from some bodies of water. Using and documenting these few simple procedures will help.
This article is based on one titled “AVOIDING THE TRANSPORT OF INVASIVE SPECIES BY SEAPLANE” written by Dr. David Strayer and Ed McNeil that first appeared in Water Flying magazine.

how seaplanes can help

There are four general rules to follow to minimize the risk of transporting invasive species by seaplane: (1) try not to transport plant fragments and other debris (including mud) from lake to lake; (2) don’t move untreated water from lake to lake; (3) be especially careful when flying from an infested body of water to a pristine one; and (4) consider all pump-out water as contaminated. Lower elevation and warmer lakes are more likely to have Eurasian milfoil, zebra mussels, or other invasive species than are higher elevation and cooler or more remote lakes. Lakes at the same elevation and in the same watershed as an infected lake may be free of invasives if they do not allow motorized watercraft and have no public launch ramp. Boat trailers and outboard motors are common transports of invasives.

Landing in the middle of a lake may avoid concentrations of floating aquatic plants found in shallow water at the shorelines. Invasives can be picked up during the approach to and stay on a beach. If an aircraft is beached or taxied to the shore, then the floats or bottom should be checked for invasives before landing in a pristine lake, or one where there is no motorized boat traffic.
Any remote lake that has no road access should be considered to be free of invasives, and deserving of our efforts to make sure we are invasive-free before landing there.

Seaplane Base Resources

There are hundreds of invasive species in North American lakes, and it is impractical to describe them all, but here are a few invasive species of special interest to seaplane pilots. More information on aquatic invaders can be found at

Stopping the Spread

Zebra Mussels

These animals look like small, black-and-white mussels (adults are ½-2 inches long). They are voracious filter-feeders that cause very large ecological changes, as well as clogging water intakes, fouling boat hulls, etc. Economic damage from zebra mussels in North America is already well over a quarter-billion dollars. Once they are established in a lake, there is usually no practical way to eradicate or even control the population. There are two ways to accidentally transport zebra mussels. The adults attach tenaciously to any solid object in the water (stones, plants, pieces of wood, boat hulls, etc.), and so can move from lake to lake on boat hulls or on bits of debris tangled on trailers, seaplane floats, and hull bottoms. The microscopic larvae can be transported in untreated water. Larval populations can be as high as hundreds per quart, so even a little bit of water can hold many larval zebra mussels, and establish a new population.

Stopping the Spread

Fishhook Waterflea

This is a tiny, shrimp-like creature that came over from Europe about 20 years ago. It now occurs in the Great Lakes and many inland lakes in the Great Lakes region. Because it is an avid predator, it has wiped out a huge number of populations of native zooplankton. It also fouls fishing lines and nets. Like the zebra mussel, the fishhook waterflea can move from lake to lake in untreated water (for instance, in a live well or bilge) or attached to weeds or lines. There are no known controls once it is established in a lake.

Stopping the Spread

Viral Hemorrhagic Septicemia (VHS)

This is probably a European disease that came into the Great Lakes in ballast water in the last 10 years. It affects many kinds of fish, and has caused massive die-offs of a number of fish species including muskellunge, walleyes, and freshwater drum. It is now spreading to waters outside the Great Lakes. Biologists are still learning about this disease, but it probably can be spread through the movement of diseased fish and contaminated water or mud, and there appears to be no control once it is established in a lake. This is a scary one.


Eurasian Milfoil, Elodea, Brazilian Waterweed, European Frogbit, Hydrilla, Water-chestnut.

 These are all invasive plants whose ecological and economic impacts and control are similar. All of these plants can clog waterways, making them useless for swimming or boating; crowd out native plants; and have large impacts on other parts of the ecosystem. Most of the plants in this list can sprout and establish a population from one little sprig (fragment), so they often are moved around on boat trailers that haven’t been cleaned properly. Water-chestnut also has a barbed seed that gets tangled up in lines, clothing, recreational gear, etc. These plants can be very difficult to control once they are established, usually requiring a sustained program of mechanical removal (by specially built harvesters, or by hand-pulling) and/or the use of herbicides. Better not to import them in the first place.