Pacific lamprey (Entosphenus tridentatus), a species facing serious threats to their existence, experience a number of challenges in reaching their desired spawning grounds during the adult migratory phase, and predators are suspected to be one of these challenges. Understanding if Pacific lamprey respond to predator odorants may provide a management tool for use in conjunction with attractants in guiding lamprey to suitable spawning habitat and deterring them from poor habitat. Previous research has failed to explore Pacific lamprey response to predator odorants, although much research exists on attractant odorants. In our study, we tested Pacific lamprey response to 4 predator odorants: white sturgeon (Acipenser transmontanus), human saliva, decayed lamprey, and river otter (Lontra canadensis). We conducted a 2 choice maze test and measured the number of entries (count) and duration of time spent in the test arm during a control trial and odorant trial. Results showed a significant (t-test; P \u3c 0.01) response to the river otter odorant, in both count and duration; however, fish spent more time and made more entries into the test arm with the treatment than with the control. This could be evidence of predator inspection and/or ‘hiding’ (remaining still). No significant difference (t-test; P \u3e 0.05) was found in the response of lamprey to the other three odors. However, tests using the decayed lamprey odorant (t-test; P = 0.47 for counts and P = 0.16 for duration) were indicative of a repellent response for duration. Results from this study indicate that Pacific lamprey respond to some predator odorants and suggest that future testing may be valuable
