Species At Risk

Northern Riffleshell

(Epioblasma torulosa rangiana)


Northern Riffleshell
Northern Riffleshell occurrences map


The Northern Riffleshell is a small (4.5 to 7.5 centimetres long), colourful freshwater mussel. The shell is brownish-yellow to yellowish-green with thin, diffuse green rays. This species can live up to 15 years. Females can be distinguished by the broadly rounded edge on the end of the shell.

Action we are taking:


In North America, the Northern Riffleshell’s range has decreased by 95 per cent. In Ontario, it is now only found in the Sydenham River and Ausable River in southwestern Ontario. Populations in Lake Erie, Lake St. Clair and the Detroit River have disappeared.


In Ontario, the Northern Riffleshell is found in riffle areas within rivers or streams with rocky, sand, or gravel bottoms. Like all freshwater mussels, this species feeds on algae and bacteria that it filters out of the water. 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 and drop off. The Northern Riffleshell is believed to have several potential fish hosts in Ontario: Blackside Darter, Fantail Darter, Iowa Darter, Johnny Darter, Rainbow Darter, Logperch, Brown Trout and Mottled Sculpin. The presence of fish hosts is one of the key features for an area to support a healthy mussel population.


The most significant threat to the Northern Riffleshell is habitat degradation due to siltation, which occurs when soil washes into the river from nearby agricultural and urban areas. Pollution and invasive species are also serious problems. The invasive Zebra Mussel, which was accidentally introduced from Europe, has been responsible for the disappearance of the Northern Riffleshell from Lakes Erie and St. Clair and the Detroit River. These invaders attach to native mussels in large numbers, causing them to suffocate or die from starvation. A decline in the population of fish hosts could also pose a threat.


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

What You Can Do to Help the Northern Riffleshell

  • The Ministry of Natural Resources tracks species at risk such as the Northern Riffleshell. 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 Northern Riffleshell 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?

The Northern Riffleshell can fish. Mussel larvae won’t survive without attaching to a fish, where they live as parasites consuming nutrients from the fish body. The female Northern Riffleshell produces a bright white lure to attract a fish and sometimes even captures it by clamping down its shell. The mussel then pumps out a cloud of larvae that attach to the stunned fish.

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.

Did you know?

Mussels are indicators of environmental health. Since mussels have complex life cycles, are long-lived species (some 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?

Northern Riffleshell may be the most imperiled mussel species we have in Ontario, as it is believed there are fewer than 15 locations where this species occurs globally.

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.