Impediments to Lamprey Spawning Migration and Development of Lamprey-Specific Fishways

Hydropower dams, culverts, irrigation diversion dams, and weirs can delay or obstruct pre-spawning migration of anadromous lampreys.  Here we review information on lamprey passage efficiency at different types of barriers and present data on behaviors exhibited when lamprey encounter obstacles.  During the past decade, we have worked to develop lamprey-specific fishways that facilitate passage of adult Pacific lamprey (Lampetra tridentata).  These prototypes provide a passage route over obstacles to lamprey movement in fishways at Bonneville Dam, the first dam these fish encounter on their spawning migration in the main stem Columbia River.  We have exploited the climbing ability of lamprey to develop structures that can be operated in a small space and afford maximal flexibility.  Improvements to lamprey fishway design require attention to attractive flows, provision of adequate attachment surfaces, recognition of swimming and climbing performance limits, and proper site selection.