Species At Risk


(Ptychobranchus fasciolaris)


Kidneyshell occurrences map


The Kidneyshell is a medium to large freshwater mussel that grows to about 12 centimetres long. As its name suggests, the shell is kidney-shaped and is thick, solid, and smooth. It is easily recognized by its shape and by its yellow-brown shell that is scattered with regularly spaced, interrupted green rays that look like squarish green spots.


In Canada, the Kidneyshell is currently found in four areas in southwestern Ontario. There are reproducing populations in the East Sydenham River and in the Ausable River. Small populations are also found in St. Clair River delta in Lake St. Clair and a tributary of the Thames River. The species no longer occurs in Lake Erie or the Detroit, Thames, Grand, Welland or Niagara rivers.


The Kidneyshell is typically found in small to medium sized rivers. It prefers shallow, clear, swift-moving water with gravel and sand. It also used to occur on gravel shoals in the Great Lakes. All mussels filter water to find food, such as bacteria and algae. Mussel larvae are parasitic and must attach to a fish host, where they consume nutrients from the fish body until they transform into juvenile mussels that drop off of the fish. The Kidneyshell has three known fish hosts in Canada: Blackside Darter, Fantail Darter, and Johnny Darter. The presence of fish hosts is one of the key features for an area to support a healthy mussel population.


The greatest threats to the Kidneyshell are pollution and siltation, which occurs when too much soil washes into the river from nearby agricultural and urban areas. The Zebra Mussel, an invasive species from Europe, is a serious threat because it attaches to native mussels and can kill them by interfering with breathing, feeding, excretion and movement. Conditions that threaten the fish host species also threaten the Kidneyshell.


The Kidneyshell is protected under Ontario’s Endangered Species Act and the federal Species at Risk Act.

What You Can Do to Help the Kidneyshell

  • The Ministry of Natural Resources tracks species at risk such as the Kidneyshell. You can use a handy online form to report your sightings to the Natural Heritage Information Centre. Photographs with specific locations or mapping coordinates are always helpful. nhic.mnr.gov.on.ca
  • Report any illegal activity related to plants and wildlife to 1-877-TIPS-MNR (847-7667).
  • Invasive species seriously threaten many of Ontario’s species at risk. To learn what you can do to help reduce the threat of invasive species, visit: ontario.ca/invasivespecies ; www.invadingspecies.com ; www.ontarioinvasiveplants.ca ; and, www.invasivespecies.gc.ca .
  • Volunteer with your local nature club or provincial park to participate in surveys or stewardship work focused on species at risk.
  • Private land owners have a very important role to play in species at risk recovery. If you find Kidneyshell in a watercourse on or adjacent to your property, you may be eligible for stewardship programs that support the protection and recovery of species at risk and their habitats.
  • You can help improve mussel habitat and keep Ontario’s water safe and clean by maintaining natural vegetation next to creeks and rivers. The roots of plants reduce erosion and can stop soil from washing into the river. Fence off streamside areas to keep cattle (and their manure) out of the water. There are many other things that you can do to help reduce soil erosion and you might be eligible for funding assistance. For more information, visit the Ontario Soil and Crop Improvement Association: www.ontariosoilcrop.org.

Did you know?

Kidneyshell larvae are clustered into packages called “conglutinates” when released, and somewhat resemble fish fry complete with eye spots, or insect larvae. When a fooled fish bites down on one of these packages, the larvae burst out and attach to the fish gills where they live as parasites and consume nutrients from the fish until they transform into juvenile mussels and drop off.

Did you know?

Mussels are indicators of environmental health. Since they have complex life cycles, are long-lived (some species can live up to 100 years!) and feed by filtering water and its pollutants, mussels can provide a snapshot of how healthy our waterways are.

Did you know?

Aboriginal people harvested mussels for food and to create jewelry and tools. In the 1800s, massive numbers of mussels were harvested from the Grand River to create buttons. Millions were shipped out every year until the 1940s when plastic buttons became more popular.

The Endangered Species Act

Contact your local ministry office

Often the best source of local information on species at risk is your nearest ministry office. Call with your questions or concerns.