Photo: CSISS

Invasive fresh water clams have been found at numerous locations in Shuswap Lake.

The Okanagan Basin Water Board says the discovery has prompted closer co-operation with the Columbia Shuswap Invasive Species Society and Shuswap government bodies.

Although the clams do not multiply as quickly as invasive zebra and quagga mussels, the introduction of the species is seen as a "dress rehearsal" for invasive mussels, the board says in its latest report.

The two groups will be reviewing the province's rapid response plan for zebra and quagga mussels, and looking at a vulnerability assessment for the region.

Corbicula fluminea are small and have a triangular shell. They are found in silty to sandy to gravel substrates in shallow areas of lakes or rivers.   

They can self fertilize and reproduce rapidly, with a single clam producing up to 70,000 eggs a year. They can spread by human transport and water currents, and have been sold for aquarium use.

Recent surveys detected live clams at Sunnybrae and Canoe on Shuswap Lake. Beach-walking surveys found shells at Sandy Point, but have not found clams at any locations outside the Salmon Arm of the lake, the Columbia Shuswap Invasive Species Society reports.

Once established, eradication of the clams from a "complex, connected water body is very unlikely and management methods are limited," the society says.

The clams are native to Southeast Asia and parts of central and eastern Australia, Africa, Indonesia and Turkey.

The primary threat is that the clams can reach high densities and cause loss of biodiversity due to competition for food and space with native species. They can alter water chemistry and cause fouling of pipes and water treatment systems.

Photo: CSISS