Ability of Adult Sea Lamprey to Climb Inclined Surfaces
Ulrich G. Reinhardt, Thomas Binder, and D. Gordon McDonald
Abstract.—Low-head barriers against invasive sea lampreys Petromyzon marinus in the Great Lakes are designed to maintain a minimum crest height of 30 cm and have a lip on the crest to prevent them from climbing over the barrier. We tested the ability of migratory-phase sea lampreys to scale inclined ramps with shallow (0.7–5 cm) water depth. We predicted that sea lampreys would jump the barrier and that their ability to attach would increase passage success. A recirculating flume and ramp with a vertical height of 10–30 cm and an inclination between 308 and 608 were used to evaluate lamprey climbing ability. Lampreys trying to scale the ramp were monitored by passive integrated transponder tag readers and low-light video cameras. No lampreys were observed jumping out of the water to scale a barrier. Independent of ramp angle, no fish passed over a 30-cm ramp. Lampreys often attached themselves to the ramp, but without a gain of vertical height between repeated attempts. The success rate at lower ramp heights varied between 0% (15 cm height, 308 angle) and 63% (10 cm height, 608 angle). Only ramps shorter than half the body length of the lampreys could be surmounted. Apparently, the lampreys had to have their dorso-ventral fins fully submerged in the downstream pool to create enough propulsion to scale a ramp in burst-swimming mode. An analysis of 1,300 passage attempts in a field-validation experiment showed a greater apparent motivation to move up a ramp but reconfirmed our laboratory findings on passage technique and maximum performance. We conclude that sea lamprey barrier height could be further reduced and that an overhanging lip is not necessary as sea lampreys neither climb nor jump over barriers. A ramp with a shallow inclination and moderate vertical height and water flow is a new design suggestion for a barrier that blocks sea lampreys and may allow other fish species to pass.