Coastal movements of migrating sea lamprey (Petromyzon marinus) in response to a partial pheromone added to river water: implications for management of invasive populations

How sea lampreys (Petromyzon marinus) search for and select reproductive habitat is poorly understood. Manual tracking of acoustically tagged migrants confirms the hypothesis that sea lampreys transition from extensive search to intensive search upon encounter with river water and return to extensive search upon leaving the plume. In addition, we document a previously unknown search tactic used to localize river mouths termed coastal rebounding. Increased intensive search in the river plume and subsequent approach to the river mouth is hypothesized to occur as a consequence of detection of a pheromone released by river resident larvae that indicate the presence of high-quality reproductive habitat. Application of two synthesized pheromone components caused migrants to increase time spent searching a plume by 57%; applications did not increase the likelihood of river entry. These findings suggest that partial pheromones constitute information that facilitates the search for river entrances, but prove insufficient to affect the decision to select a habitat. Proposed management tactics that rely on luring migrants into rivers with larval odor may prove ineffective without a complete blend of pheromone components.