A Few Newcomers in the Rideau RiverSnails
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]
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]
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]
The greatest threat to native freshwater mussels in the Rideau River is from the invasion of the zebra mussel (Dreissena polymorpha).
|Last Update: 2007-05-18|
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