By Jacqueline Madill and Meaghan Murphy

Watch out! Zebra mussels may be coming to an area near you. Disturbing sightings of this invasive species on the Ottawa River has spurred the creation of a zebra-mussel citizen-watch programme in the Ottawa River watershed.

A couple dozen zebra mussels in the palm of a hand.
Zebra mussels found in Lac Deschênes, Ottawa River. Image: André Martel © Canadian Museum of Nature

The discovery of zebra mussels (Dreissena polymorpha) in a new location on the Ottawa River was brought to the attention of André Martel, Ph.D., at Canadian Museum of Nature. This spring, Martel confirmed the arrival of the invasive zebra mussel on boats and anchors in Lac Deschênes, a reach upstream of Ottawa that we hoped would avoid invasion.

Many zebra mussels cling to a large mussel that is on its side on the river bottom.
Underwater view of a freshwater native mussel in the process of falling over from the heavy weight of the attached zebra mussels. Image: André Martel © Canadian Museum of Nature

In response to this discovery, Ottawa Riverkeeper and the Canadian Museum of Nature joined forces to develop a Zebra Mussel Watch Program for riverwatch volunteers who live along the Ottawa River.

People on a dock on the river.
Newly minted citizen scientists: the volunteer riverkeepers who will be monitoring the zebra-mussel populations in the Ottawa River.

On July 10, 2015, a training session for the monitoring programme was held at the Ottawa Rowing Club as part of Ottawa Riverkeeper’s annual Riverwatch Meeting. Over 40 riverwatchers were trained by museum researcher Jacqueline Madill on how to distinguish zebra mussels from our native marine and native freshwater mussels, as well as how to conduct shoreline surveys. Important but not identifying characteristics: native marine mussels are scrumptious and native freshwater mussels are the best organisms for filtering water clean.

Two women hold a cement block by the river.
Meaghan Murphey (left), an Ottawa Riverkeeper, and the museum’s Jacqueline Madill hold a cement block that was handed out to riverwatchers. Image: Joe Ryan © Canadian Museum of Nature

Martel and Madill designed a simple zebra-mussel collector, needed for estimating their settlement patterns: a standard cement block lowered into the water. At summer’s end, the number of adults that accumulated on the block is counted. This method allows comparisons to be made throughout the watershed with the help of many volunteers. A fine example of citizen science!

Zebra mussels arrived in the Great Lakes in 1986 from ballast waters of vessels from Europe. Their veliger larvae drift in water after spawning, subjected to current flow. A female zebra mussel can produce up to a million larvae in a single summer.

A woman sits at a table and holds the specimen.
A participant at an Ottawa Riverwatch meeting examines a freshwater mussel shell that has become covered with zebra mussels. Image: Joe Ryan © Canadian Museum of Nature

In two to three weeks, zebra mussels settle and attach with byssal threads to any hard substrate that they can find, such as rocks, plastic, shells and even other zebra mussels. In a river, the larvae can travel in only one direction, and downstream portions of the Ottawa River are in danger.

One mussel of 1.5 mm and one of 5 mm.
Microscope photographs of newly settled zebra mussels holding onto substrates with their byssal threads. The specimen on the left is attached to a kitchen scouring pad. Note that the scouring fibres are green with algae. The older specimen on the right is crawling across a glass slide as it is being observed under a microscope. The white byssal threads can be seen on the glass slide. Image: André Martel © Canadian Museum of Nature

To travel upstream and to other bodies of water, zebra mussels require the assistance of humans. That is where we come in. Zebra mussels travel well on boats, trailers and vegetation caught in the motor, and they can live for several days out of water. We have to clean anything that can transport zebra mussels from one water body to another.

With citizen scientists tracking the distribution and movements of this invader, and everyone’s effort on boat washing, their spread upstream can be prevented. Let’s focus on critical regions within the watershed that are at risk.

Vigilance is important because we do not know of any way to get rid of these destructive pests once they are established.