Aquatic Species at Risk - Rayed Bean

Also see - Central & Arctic Region, Species Fact Sheet in PDF version

At a glance

Once ranging from western Lake Erie to rivers in the Lake St. Clair drainage, the Canadian population of the Rayed Bean is found today only in the middle reach of the Sydenham River—its population struggling with the environmental pressures of pollution and the invasive Zebra mussel.

About the Rayed Bean

A tiny mussel, the Rayed Bean subsists on detritus, bacteria and algae floating in the waters where it lives. Its host fish in Canada is the Greenside darter; in the U.S. its host is the Tippencoe darter.

How to recognize the Rayed Bean

Just under 40 millimetres long and 19 millimetres high, the Rayed Bean is often easy to overlook. It takes its name from the wavy green rays that mark its elliptical body. The inside of its shell is silver-white and iridescent.

S. Staton, National Water Research Institute, Environment Canada

Where the Rayed Bean lives

The Rayed Bean buries itself in sand and gravel at the roots of aquatic plants; because of this, it can sometimes be hard to find. Records over the years suggest that the population of Rayed Bean has declined, although there are indications that it continues to reproduce successfully.

Why it’s at risk

The availability of shallow, silt-free riffle habitat is probably the main limiting factor for this species. Agricultural and forestry practices cause siltation, which can bury mussels, interfere with their feeding, and expose them to pollutants. The Rayed Bean may be more directly exposed to sediment-associated contaminants than most other species of freshwater mussels because it buries relatively deeply. It is also susceptible to negative effects from exposure to agricultural chemicals such as fertilizers and pesticides.

What’s being done

The Rayed Bean is protected under several pieces of legislation, including the federal Species at Risk Act (SARA), the federal Fisheries Act, and Ontario Fishery Regulations. The species is one of many whose recovery is being dealt with through the Sydenham River Ecosystem recovery plan. The goals of that plan include maintaining current populations and distributions of species at risk, improving water quality, establishing a broad-based monitoring program, preventing the introduction of non-native species and promoting good land stewardship practices.

Consideration of the Rayed Bean is also being built into a recovery plan for Ontario’s Thames River ecosystem.

Consult the Recovery Strategy for Rayed bean :
Recovery Strategy for Northern Riffleshell (Epioblasma torulosa rangiana), Snuffbox (Epioblasma triquetra), Round Pigtoe (Pleurobema sintoxia), Mudpuppy Mussel (Simpsonaias ambigua) and Rayed Bean (Villosa fabalis) in Canada (2007)

What can you do?

This species will get the protection it needs only if all Canadians work together to reduce threats. Find out more and do your best to reduce these threats wherever possible to better protect its critical habitat. Get involved with the Habitat Stewardship Program for Species at Risk (HSP) or another conservation organization.

Background information provided by Environment Canada in March 2004.