Scientific Name: Obovaria olivaria
Taxonomy Group: Molluscs
Range: Ontario, Quebec
Last COSEWIC Assessment: May 2011
Last COSEWIC Designation: Endangered
SARA Status: No schedule, No Status
Image of Hickorynut
The Hickorynut is one of Canada’s 54 freshwater mussel species and one of only two mussels in the genus Obovaria found in Canada. Also known as the Olive Hickorynut, this small-to-medium sized mussel is easily recognized by the following features: Nearly oval-shaped shell, no longer than 7.5 centimeters; shell colour is green to yellowish-brown, turning dark brown with age; thin, greenish coloured rays can often be seen on juvenile shells; inside of shell (nacre) is usually bright white and often iridescent towards the back (posterior); shell is thicker in the front (anterior) and thinner at the back (posterior); posterior of the shell is broadly pointed in males and rounded in females; beaks are elevated, raised above the hinge line and set towards the extreme anterior of the shell; and hinge teeth are complete, thick and well defined.
Distribution and Population
Historically, the Hickorynut was widely distributed along the large river bottoms of the Mississippi River drainage system and the Great Lakes-St. Lawrence basin. While still broadly distributed in the Mississippi drainage of the United States, the Hickorynut is imperiled or lost from most of the American Great Lakes states. In Canada, current populations are now only found in certain rivers and their tributaries within the Great Lakes-St. Lawrence drainage system, from Lake Huron in southern Ontario to Quebec City in the east. Rivers include the Mississagi River, Ottawa River, St. Lawrence River and the Saint Francois River.
Hickorynut are typically found in the sandy bottoms (substrates) of large, wide and deep rivers (2–3 metres or deeper) with moderate to strong currents.
Hickorynut are fairly long-lived mussels, with a lifespan between 7 and 14 years. The Hickorynut is considered a long-term brooder; spawning happens in the fall and the larvae (glochidia) are released the following summer. Like most other freshwater mussels, Hickorynut glochidia are parasitic on fishes—the glochidia attach to and feed off the gills of a host fish until they reach their juvenile, free-living stage and drop off to burrow in the substrate below. Adult Hickorynut are essentially sessile and may move only a few meters along the substrate the entire rest of their lives. Like all species of freshwater mussels, they filter food from the water. Bacteria and algae are its primary food sources.
The introduction of Zebra and Quagga mussels in the 1980s and 90s wiped out the Hickorynut in the Detroit and upper St. Lawrence rivers. The invasive mussels attach to Hickorynut shells by the hundreds, preventing them from eating, breathing, moving and reproducing, and continue to threaten the remaining Hickorynut populations. Dams along the large river habitats of the Hickorynut are another serious threat, as its suspected host fish, the Lake Sturgeon, are unable to traverse them. With fewer hosts, the chances of enough larvae reaching their free-living stage to maintain the population are greatly reduced. Pollution from industry and agriculture also threaten the Hickorynut and its host by decreasing the water quality of the habitat.
In Canada, this species is currently under consideration for listing as Endangered under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available online at AquaticSpeciesAtRisk.ca or on the SARA Registry at SaraRegistry.gc.ca.
Provincial and Territorial Protection
Other Protection or Status
The Hickorynut is listed as Endangered under Ontario’s Endangered Species Act, 2007, and is anticipated for listing under Quebec’s Act respecting Threatened or Vulnerable Species. If listed under the SARA, a recovery strategy and action plan will be developed to prevent the loss of the Hickorynut in Canada, involving research, land and water stewardship, monitoring and awareness activities. Critical habitat for the Hickorynut will also be identified under the SARA, allowing for greater protection and recovery of its habitat.
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
4 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- Response Statements (1 record(s) found.)
- COSEWIC Annual Reports (1 record(s) found.)
- Consultation Documents (1 record(s) found.)
COSEWIC Status Reports
COSEWIC Annual Reports
- Date modified: