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Native Freshwater Mussels


Genuine Water Filtration Plants!

Eastern elliptios, Elliptio complanata, under water.
The openings through which eastern elliptios (Elliptio complanata) filter water for food and oxygen can be seen here.

Native freshwater mussels are the Rideau River's powerful water filtration system. Each mussel filters up to 38 litres (about 8 gallons) of water per day. Because mussels, which are also called clams, feed on single-celled algae and bacteria such as E. coli, their importance in keeping the water clean cannot be underestimated.

There are 8 native species of mussels known to live in the Rideau River. Similar numbers of native species are found in other Eastern Ontario rivers. The most common native species in the Rideau River are the eastern elliptio mussel and the eastern lamp-mussel. The rarest mussels in the Rideau River are the ridged wedge-mussel and the squaw foot mussel.

A bed of native freshwater mussels.
A bed of healthy native freshwater mussels.

The Rideau River Biodiversity Project found that mussels are most varied and abundant upstream from Burritts Rapids, Andrewsville, and the Old Slys lockstation. All eight species were found alive in these locations.

The least variety and abundance of living mussels were found near Manotick, Billings Bridge, Mooneys Bay and Sandy Hill. The most dead mussels were found in these same locations. In some of these locations, not one mussel was found alive.

Mussels are sensitive to water pollution and deterioration of the environment. The more species found in a location and the greater their abundance, the better the health of the aquatic environment and the cleanliness of the water.

Zebra mussels (Dreissena polymorpha) on an eastern lampmussel (Lampsilis radiata).
Zebra mussels (Dreissena polymorpha) have attached themselves to an eastern lampmussel (Lampsilis radiata).

Threatened Populations

Native freshwater mussels partially bury themselves in the sand, mud or gravel of the river bottom. Mussels are a source of food for birds, turtles, some fish, and mammals such as muskrats.

Regrettably, a number of threats menace the native freshwater mussels of the Rideau River. The most obvious, without a doubt, is the growing presence of zebra mussels. This exotic mussel species is native to Europe. Zebra mussels attach themselves to hard surfaces, such as the shells of other mussels. In doing so they interfere with the normal feeding, breathing and movement of the native species.

Zebra mussels are not the only culprits responsible for the decline in freshwater mussel populations. Deterioration of riverbanks and pollution alter their habitats and cause the fish species that are essential to the freshwater mussels' reproductive cycle to flee. Also, sediments washed in from the River's tributaries or stirred up during water level fluctuations blanket freshwater mussels and prevent them from breathing and feeding.

Effects of the Presence of Zebra Mussels on Native Mussels of the Rideau River
Table: Effects of the Presence of Zebra Mussels on Native Mussels of the Rideau River, 1993.
Legend for the tables (1993 and 1999): Effects of the Presence of Zebra Mussels on Native Mussels of the Rideau River. Texts: Diversity of native freshwater mussels, Density of zebra mussels.
Table: Effects of the Presence of Zebra Mussels on Native Mussels of the Rideau River, 1999.

A Valuable Source of Information
Sandshell, Ligumia recta.
Ligumia recta.
A special feature of mussels is that, dead or alive, they are a very valuable source of information about the quality of the aquatic environment.

In an environment such as the Rideau River, decades can pass before mussel shells disintegrate. By examining the shells of the dead mussels accumulated on the river bottom, researchers can discover which species have lived there, even if they don't find any specimens alive.

In 1993, shells of dead sandshells were found near Billings Bridge in Ottawa, long before the zebra mussel invaded. No specimen was found alive during the work, which continued until 2000. The researchers concluded that environmental degradation led to the disappearance of the sandshells at this location.

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 Native Mussels
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