First record of nest building, spawning and sexual dimorphism in the threatened Cowichan Lake lamprey Entosphenus macrostomus

The Cowichan Lake lamprey Entosphenus macrostomus is a parasitic freshwater fish endemic to Cowichan, Mesachie and Bear lakes in British Columbia, Canada. Its restricted distribution and inherent vulnerability to localized threats were principal factors resulting in this species being listed as 'threatened' under Canada's Species at Risk Act. This study documents the first report of nest building, spawning and sexual dimorphism in E. macrostomus. Preliminary data such as spawning locations and nest size will inform the management and protection of this species and its habitat as a Species at Risk, as well as future research.