Critical Habitat and the Conservation Ecology of the Freshwater Parasitic Lamprey, Lampetra macrostoma

Lampetra macrostoma, the Cowichan Lamprey, is a freshwater parasitic lamprey that probably evolved from L. tridentata within the last 10 000 years. It is unique to the Cowichan Lake watershed on Vancouver Island, British Columbia, Canada. Larval rearing in Mesachie and Cowichan lakes occurs in shallow, silt-covered gravel areas at the mouths of rivers and streams flowing into the lakes. Spawning occurs over a protracted period from early May until about late July. Shallow areas with small gravel along the shore of the lakes, near the mouths of rivers are essential for successful spawning. Adults prey on a variety of salmonid species within the lake. There has been considerable development around Mesachie Lake and reported increased fishing pressure on prey in Mesachie and Cowichan lakes. It is not known if the size of the population of L. macrostoma has changed since an initial study in the early 1980s, but a study in 2008 captured very few spawning lamprey in Mesachie Lake, possibly indicating that the population is declining.