Behavioural response of larval sea lamprey (Petromyzon marinus) in a laboratory environment to potential damage-released chemical alarm cues

Sea lampreys (Petromyzon marinus L., 1758) invaded the Great Lakes early in the 20th century and have caused economic and ecological damage to native fish species. The integrated sea lamprey control program involves low-head barrier dams, lampricides, and trapping. The search for low cost and less toxic alternatives to lampricides could involve the use of repellents in the form of chemical alarm cues. The objective of this study was to determine whether larval sea lamprey showed a behavioural response when exposed to damage-released chemical alarm cues by increasing their swimming time, rate of direction changes, or rate of escape attempts in an artificial stream channel experiment. Larval sea lampreys were exposed to conspecific larval sea lamprey extract, heterospecific swordtail (Xiphophorus hellerii Heckel, 1848) extract, or a distilled water control. The larvae increased their rate of escape attempts after exposure to both swordtail and larval lamprey extracts and their rate of direction changes after exposure to sea lamprey extract. However, larvae did not increase their swimming time in response to any experimental stimuli. This is the first study to suggest that larval sea lamprey respond to potential chemosensory risk assessment cues.