Assessing Pacific lamprey status in the Columbia River basin
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In the Columbia River drainage, salmonid-based monitoring programmes have historically been used to assess status of both adult and juvenile Pacific lamprey (Lampetra tridentata). We compared adult lamprey counts at hydropower dams to recent radiotelemetry results and found that the counts underestimated losses between some dams and overestimated passage times through reservoirs. Count data were not correlated with trap captures of adults conducted in the same area and at the same time, likely due to lamprey-specific behaviours that result in inaccurate counts. We recommend maintenance of traditional count protocols, but emphasize the need for continued research to develop an accurate correction factor to apply to these data. Existing salmonid-based sampling for juvenile lamprey is inadequate and we highlight the need for standardized larval lamprey monitoring that provides both abundance and size distributions. Our electrofishing survey for juvenile lamprey indicated that this technique provides critical information on lamprey recruitment and is feasible over large spatial scales.