Pavilion Lake - Fresh Water Coral Dive

Incredible visiblity and coral formations make this site a must see. Contact the store for more information on this exciting dive.

http://supercritical.civil.ubc.ca/~pavilion/information/site_descr.htm

HAVE YOU SEEN THIS RARE OKANAGAN INVERTIBRATE????

WESTERN RIDGE MUSSEL
Gonidea angulata
Family Unionidae - Pearly Mussels
Order Eulamellibranchia - Clams and Mussels
Risk Status
Official status

Freshwater molluscs are not included in a list of rare and threatened terrestrial and freshwater invertebrates of British Columbia because little is known of their distribution and status. Though elsewhere in North America they are among the most vulnerable of invertebrate groups to environmental degradation.

Image Credits: Western Ridge Mussel sketch in 'Rare Invertebrates of the South Okanagan' by Hannah Nadel

image from: Fresh Water Molluscs of Canada,
Arthur H. Clarke. Courtesy of the Canadian
Museum of Nature, Ottawa, Canada.

Distinguishing features

Another common name for the Western Ridge Mussel is the Rocky Mountain Ridged Mussel.

The shell of the Western Ridge Mussel is up to 125 mm long, 65 mm high, 40 mm wide, and with a shell wall up to about 5 mm thick at mid-anterior. They are variable in form but typically rather thin, trapezoidal in shape. They are yellowish brown to blackish brown on the outside and centrally white or salmon to pale blue on the inside of the shell.

The beak sculpture is compose of about 8 rather coarse, concentric ridges that are straight in the centre and curved at both ends. The hinge teeth are irregular and poorly developed.

Distribution

Red dots indicate museum specimen records or confirmed breeding sites.

British Columbia
The Western Ridge Mussel has been found in the Columbia River system in southern British Columbia (Okanagan and Kootenay rivers). This freshwater mussel is known in Canada only from the main, valley bottom water bodies from Penticton south. There have been few searches for it, and the only recent records are from the Okanagan River at Okanagan Falls, Vaseux Lake and Osoyoos Lake.

North America
The Western Ridge Mussel is found south in the Pacific drainage to southern California.

Habitat

In Vaseux Lake near Oliver, British Columbia, large specimens of the Western Ridge Mussel occur in muddy sand at a depth of 0.6 to 0.9 m along the shoreline edge of a bed of pond weed. Elsewhere it occurs in rivers and lakes and on various substrates. Four specimens were collected on 6 August 1972 from Vaseux Lake, and none were gravid.

Why is it endangered?

Rare invertebrates of the south Okanagan and Similkameen valleys such as this species are threatened not by direct exploitation, but by loss or degradation of their habitats. They are at risk because their ecosystems are at risk.

The massive diversity of invertebrate species in British Columbia makes it very difficult for entomologists to do a literature or collection survey to determine which species are endangered or threatened. Specialized, detailed surveys will be required for almost every species that is suspected of being endangered. Despite a general ignorance about invertebrate distribution, information is known about a number of species that are confined to threatened habitats of very limited extent in the Thompson-Okanagan valleys.

The unionid mussels - the family that the western ridge mussel belongs to - are very sensitive to environmental changes and consequently have a high percentage of endangered species within their ranks throughout North America.

Please report any seittings to The Conservation Data Center

Contacting the CDC

Mailing address:
B.C. Conservation Data Centre
Ecosystems Branch
Ministry of Environment
P.O. Box 9358 Station Provincial Government
Victoria, BC. V8W 9M2

Location/courier address:
B.C. Conservation Data Centre
Mezzanine, 395 Waterfront Crescent,
Victoria, BC. V8T 5K7

Phone: (250) 356-0928 Toll Free through Enquiry B.C. (instructions below)
Fax: (250) 387-2733
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