Drag Force Physical Modeling for Use in Design of Lamprey Passage Structures (LPS)

Typically, fish passage design relies on the critical swim speed to establish the upper limit of the mean velocity within a fishway for a target fish species.  We applied an alternative drag-based approach for use in design of Pacific Lamprey (Entosphenus tridentatus) Passage Structures (LPS) within the Columbia River drainage to predict Pacific Lamprey success in LPS because velocities therein can exceed the velocity barrier of the fish.  We investigated varying slopes and discharges to explore the hydraulics of Pacific Lamprey climbing behavior.  Our investigation assessed the dead drag forces at four levels of static submergence: fully submerged (120 mm), equally submerged (40 mm), partially submerged (15mm), and skin flow (5mm) for a Pacific Lamprey model of median adult body size.  We then used the results to establish drag thresholds corresponding to the known critical swim speed and velocity barrier of the fish, and applied the results to predict passage success relative to submergence.  The results are scalable according to fish size, and directly applicable to energy, work, and power estimates for Pacific Lamprey passage.  Implementing a similar approach could be used to improve native passage at fishways, or applied when attempting to prevent invasive species passage (e.g. sea lamprey).