Swimming behaviour of juvenile Pacific lamprey, Lampetra tridentata

SynopsisWe collected actively migrating juvenile Pacific lamprey Lampetra tridentata [Richardson, J. 1836. Fauna Boreali-Americana; or the zoology of the northern parts of British America: containing descriptions of the objects of natural history collected on the late northern land expeditions, under the command of Sir John Franklin. R.N., Fauna Boreali-Americana, 327 pp.] from hydroelectric bypass facilities in the Columbia River and transferred them to the laboratory to study diel movement patterns and swimming ability. Volitional movement of lamprey was restricted mainly to night, with 94% of all swimming activity occurring during the 12 h dark period. Burst speed of juvenile lamprey (mean length 136 ± 5 mm SD) ranged from 56 to 94 cm s−1 with a mean of 71 ± 5 SD cm s−1 or an average speed of 5.2 s−1 body lengths (BL). Sustained swim speed for 5 min test intervals ranged from 0 to 46 cm s−1 with a median of 23 cm s−1. Critical swimming speed was 36.0 ± 10.0 SD cm s−1 and 2.4 ± 0.6 SD BL s−1. We found no significant relationship between fish length and critical swimming speed. These findings show that swimming performance of juvenile Pacific lamprey is low compared to anadromous teleosts. Their poor swimming ability provides a challenge when they encounter man-made structures and reservoirs during the freshwater migration interval downstream to the Pacific Ocean.