Image reproduced with permission from the Canadian Museum of Nature, Ottawa, Canada.
SARA Status: Special Concern, Listed under SARA (2005)
COSEWIC Status: Endangered (2010)
To reproduce, males release sperm into the water column; females then receive sperm during the process of filter feeding and fertilize the eggs. Larvae are typically released from the female in spring and early summer. After drifting passively until they contact a suitable host fish, they attach to its gills or fins and remain for approximately one to six weeks while transforming into a juvenile mussel. As juveniles, they drop off the fish and begin a free-living benthic life. From counts of annual growth rings, it is believed Rocky Mountain ridged mussels can live up to about 30 years.
The Rocky Mountain ridged mussel is a large freshwater mussel. Its typically thin shell is trapezoidal and up to 12.5 cm long and 0.4 cm wide. Like that of all other mussels, the shell of this species is composed of two parts, known as valves, connected by a hinge. This hinge is medium-sized and has small, irregular, indistinct anterior teeth. The surface of the shell is marked by well-defined growth rings, and the dorsal valve is distinguished by a sharp, prominent ridge at the beak. For juveniles, the outside of the shell is greenish or ochre, while adults are typically darker, becoming bluish-black. The inside of the shell is white tinged with coppery blue.
The Rocky Mountain ridged mussel lives in fresh water. It is found in various sizes of lakes and streams where the flow is constant and especially where the bottom is composed of fine material, though they have been found wedged within cobbles. They are found in shallow water and may be in deeper water.
The Rocky Mountain ridged mussel is threatened by the destruction and degradation of its habitat. Like all members of this family of mussels, it is highly sensitive to changes in its environment, such as those affecting the temperature or composition of the water. Additionally, because mussels filter large volumes of water in order to feed, they are susceptible to dissolved pollutants building up in their bodies. The proliferation of exotic species such as zebra mussels is also a source of concern.
The Rocky Mountain ridged mussel will get the protection it needs only if all Canadians work together to reduce threats. Find out more about the Rocky Mountain ridged mussel and be aware of human-induced threats. Do your best to reduce these threats and better protect the habitat of this species at risk by getting involved with the Habitat Stewardship Program for Species at Risk (HSP) or another conservation organization.
This species occurs from southern British Columbia to southern California and eastward to southern Idaho and northern Nevada in the United States. In Canada, they are limited to the Columbia River system and its tributaries, including the Okanagan and Kootenay rivers. This species is probably also present in other similar areas in southern British Columbia.
A management plan is currently being developed by Fisheries and Oceans Canada and the Province of British Columbia.
Scientific name: Gonidea angulata
Taxonomy: Mollusc (freshwater)