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Exotic Species

 

View of the Rideau River.
The Rideau River, near Billings Bridge.

A Few Newcomers in the Rideau River

Snails
Mud bithynia
The mud bithynia (Bithinia tentaculata) is a small snail that lives under rocks. Its shell is smooth and tapers to a slender point. The species was introduced from Europe into the Great Lakes in 1871 in the ballast water of ships and in the marsh grass that was used to pack crockery.

This exotic species was introduced into the Rideau River about a century ago and has since spread like wildfire through the rocky sections of rapids in the Rideau River, areas where the river bypasses the canal locks. At Burritts Rapids this species has displaced almost all species of native snails that live under rocks and stones.

A group of scientists and volunteers from both the Canadian Museum of Nature and the Eastern Ontario Biodiversity Museum measured a pile of empty shells they found in a cavity on the River bottom near Burritts Rapids. The pile was 3.8 m wide by 5.6 m long and 1.2 m deep - an estimated 120 million shells!

The mud bithynia population has stabilized, although it continues to dominate the snail fauna in rocky sections of the Rideau River. Before the zebra mussel arrived in the Rideau River, the mollusc fauna was already overwhelmingly dominated by an introduced exotic species. [3, 4, 5, 6]

Banded mysterysnail
The banded mysterysnail (Viviparus georgianus) has a large yellow to olive, spherical shell that is striped with dark reddish bands. The snails are native to the Mississippi River watershed in the U.S. They live in lakes and slow moving rivers, usually on muddy bottoms among vegetation.

This species is a popular aquarium species and its spread into the Great Lakes and Rideau River is the result of aquarium releases. These snails are common in Mooneys Bay, but are in the process of becoming supplanted by another exotic mollusc, the zebra mussel. [3, 4, 5, 6]

Chinese mysterysnail
Chinese mysterysnails (Cipangopaludina chinensis) are easily identified by their very large non-banded green shells. Native to Asia, this species has been dumped from aquariums into the Rideau River.

In some parts of Eastern Ontario, Chinese mysterysnails are extremely abundant and are known to clog the water intakes of power plants. In the Rideau River, Chinese mysterysnails are regularly seen in the Ottawa area. [3, 4, 5, 6]

Zebra mussels, Dreissena polymorpha.
Zebra mussels, Dreissena polymorpha.
Mussels and Clams
Zebra mussel
The greatest threat to native freshwater mussels in the Rideau River is from the invasion of the zebra mussel (Dreissena polymorpha).

European fingernailclam
The European fingernailclam (Sphaerium corneum) is a tiny burrowing mussel that is native to Europe and Asia. It was first discovered in the Great Lakes in 1962. It is not known how or when this species was transported from abroad or how it spread to the Rideau River. The effects of the European fingernailclam are not known. [3, 4, 5, 6]


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 Newcomers
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 Exotic Species
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A Project of the Canadian Museum of Nature
 Images: Ed Hendrycks, Diane Pathy