Passage Options for Climbing Lamprey: If You Build it They Will Come

Barrier passage is an impediment to the movement of many species of lamprey worldwide. Methods such as velocity reduction, lamprey-friendly structural modifications, and lamprey-specific fishways have been implemented to improve riverine migration. We will describe approaches geared at climbing species navigating both large and small in-river impediments. This work is part of efforts to understand and improve the passage performance of adult Pacific lamprey (Entosphenus tridentatus) in the Columbia River basin.

We designed an experimental vertical climbing structure that could collect and pass lamprey without impacting co-occurring salmonid species. To test Pacific lamprey vertical climbing ability in relation to flow, the apparatus was outfitted with three regulated water delivery mechanisms. All of the lamprey that attempted to climb the experimental wetted wall were ultimately successful, regardless of the flow level or water delivery type. Behavioral observations suggest some refinements to the climbing structure. Lamprey climbing success from these trials shows that a vertical wetted wall could be a useful component of efforts to improve passage for climbing lamprey. Such structures could be used to collect lamprey and direct them into alternative routes with existing passage, over small barriers, or into larger lamprey passage systems in locations with structural constraints.