Field evaluation of larval odor and mixtures of synthetic pheromone components for attracting migrating sea lampreys in rivers.

The sea lamprey, Petromyzon marinus, is a harmful invader of the Laurentian Great Lakes. The odor emitted by larval lampreys resident to streams attracts migrating adults to high quality spawning habitats. Three components of the larval pheromone have been identified and tested in laboratory settings: petromyzonol sulfate, petromyzosterol disulfate, and petromyzonamine disulfate. Here, we report the first field test of six mixtures of synthetic versions of these pheromone components, and we compare lamprey responses to these with those elicited by the complete larval odor in a natural stream. Exposure to larval odor both increased upstream movement and attracted migrants into the portion of a channel containing the odor. No tested combination of synthetic pheromone components proved similarly attractive. These findings suggest the existence of unknown additional components of the pheromone that await discovery and are likely necessary if the pheromone is to be useful in management of this pest. Further, we hypothesize that the complete pheromone mixture is necessary to attract migrants into spawning habitat at the conclusion of the migration, whereas a partial pheromone may be effective at the transition from lake to stream when natural factors both dilute and alter the ratio of components from that actually emitted by sea lamprey larvae.