Behavioural threshold of adult and juvenile sea lamprey (Petromyzon marinus) to acoustic stimuli

Sea lamprey (Petromyzon marinus Linnaeus, 1758) are invasive fish species in the Laurentian Great Lakes and parasitically feed on many commercially important fishes. Sound is used as a deterrent for invasive species, but its potential for manipulating sea lamprey behaviour in natural stream conditions is under-tested. Both the behavioural acoustic thresholds and different life stage responses of sea lamprey have yet to be established. To fill in some literature gaps, low-frequency tones of 70 or 90 Hz were used in a laboratory setting to determine the behavioural responses of adult and juvenile sea lamprey. Both stages of sea lamprey exhibited a change in swimming behaviour (movement to the onset and offset of sound) and a twitch (small movement of tail or body) in response to both frequencies. The behavioural threshold for adult and juvenile lamprey to sound ranged from 147-162 dB re 1 μPa. The threshold level for twitch determined for 70 Hz for juvenile and adult sea lamprey ranged from 157-160 dB re 1 μPa. These thresholds and behaviours can be used for implementation of field management techniques that have previously shown the efficacy of sound to direct lamprey movements for control purposes.