Abstract
The ability of adult Pacific lamprey, Entosphenus tridentatus (Gairdner), to climb has enabled development of lamprey‐specific fishways. Sheer vertical climbing elements are needed for these structures when fishway installation space is limited. A 1.6‐m high aluminium wetted wall was built to test Pacific lamprey vertical climbing in relation to flow and three water delivery mechanisms: overflow, upwelling and sidewelling. Passage success and passage times were recorded for individual Pacific lamprey ( n = 122). For those that interacted with the structure ( n = 104), 94% successfully ascended the wall (76% on their first attempt). Average time from first interaction with the structure to exit ranged from 19.5 to 47.0 min. Success rates and passage times were not significantly affected by flow or water delivery treatments. This indicates that vertical elements can facilitate lamprey passage in the 0.13–3.59 L min −1 cm −1 flow range tested and may greatly expand the design alternatives in certain situations.