**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION. The title, authors, and abstract for this completion report are provided below.  For a copy of the full completion report, please contact the author via e-mail at mwagner@msu.edu. Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**

Altering migratory routes of sea lamprey through push-pull application of semiochemicals

C. Michael Wagner¹, Gregory J. Byford¹, James R. Miller², Muraleedrahan Nair³

Michigan State University

East Lansing, MI 48824

¹Department of Fisheries and Wildlife, 480 Wilson Rd., Rm. 13

²Department of Entomology, 578 Wilson Rd., Rm. 203

³Department of Horticulture, 1066 Bogue St., Rm. A420

December 2016

ABSTRACT:

The act of migration often requires prey to move into regions of heightened predation risk. During the return migration in the Great Lakes, the sea lamprey (Petromyzon marinus) transitions from lakes to rivers, choosing habitat in response to the presence of odor emitted by stream-resident larval lampreys. This odor represents an ecological legacy, advertising the location of high-quality spawning and rearing habitat to the non-homing migrants seeking to reproduce. When attacked or killed during the migration, the sea lamprey releases a powerful alarm cue; a chemical substance of unknown structure that alerts conspecifics to the presence of predation risk. Previous research has established that each odor, acting singly, is used to guide the selection of movement paths in streams. The larval odor attracts migrants to the side of the river associated with good habitat, the alarm cue repels them from areas associated with risk. The goal of this project was to begin to map how migrating sea lamprey respond to the odors in concert, both when overlapping (competing information) and when spatially separated (contrasting information). Two general research questions were addressed. First, will the sea lamprey respond to the alarm cue in a threat-sensitive manner (increasing avoidance with increasing concentration) such that a river containing larval odor may be chemically ‘blocked’ by the application of a suitably-high concentration of alarm cue? We tested this response in a natural stream containing a population of larval sea lamprey. In the presence of larval odor upstream, no application of the alarm cue was sufficient to halt upstream migration. There was evidence that the animals slowed their upstream movement, but the decision to continue migrating was unaffected (Manuscript #1). Second, we examined the effects of five contrasting chemical information scenarios on the decision to move upstream, side of the channel selected for movement, and the timing of movement, as follows: (1) larval odor vs. river water (opportunity only), (2) alarm cue vs. river water (avoidable risk, no opportunity), (3) alarm cue vs. alarm cue (unavoidable risk, no opportunity), (4) alarm cue vs. larval odor (avoidable risk coupled with opportunity), and (5) alarm cue + larval odor vs. alarm cue (unavoidable risk coupled with opportunity). In this experiment the migrating lampreys clearly modulated their upstream movement tendencies, with the lowest movement during risk-only scenarios, and the greatest movement with avoidable risk and opportunity, or opportunity alone (Manuscript #2). Clearly, both larval odor and the alarm cue are used by the animal to select risk-minimizing (or safe) routes towards habitat chemically labeled by living larvae. While the alarm cue was a powerful motivator of movement paths, the greatest effect was observed when the odors reinforce each other (e.g., attractant on one side, repellent on the other). Such an application (often labeled ‘pushpull’) should prove highly effective in guiding lampreys into target tributaries at confluences, or into areas targeted for other means of control (e.g., traps). The project developed no evidence that the alarm cue may be used to chemically block a stream in the presence of larval odor. Finally, in a third experiment that arose opportunistically, we discovered that the Pacific lamprey (Entosphenus tridentatus) contains an alarm cue that is also highly repellent to the sea lamprey, suggesting the species share components of the cue. The sea lamprey may prove a useful surrogate species for studying methods to conserve imperiled lampreys (Manuscript #3).