Can We Manipulate Reproductive Migrations? Lamprey Search Behavior and Habitat Selection Presents Opportunities for Improved Conservation

Behavioral manipulation is a coveted means of managing invasive and conserved fishes, especially when the interventions avoid non-target impacts. Understanding the mechanisms underlying search and habitat selection (decision-making) may reveal opportunities for manipulation. We report how invasive sea lamprey, Petromyzon marinus, return to coastal environments, locate river plumes and enter rivers in the Great Lakes during their spawning migration. VEMCO acoustic-arrays provided 3D paths (30s intervals, <5m-accuracy) of lamprey movement in an offshore array as the animal attempted to locate the shoreline (N=23, 2012), and on the coast near the Ocqueoc River (n=153, 2010-2011). The offshore array revealed that sea lamprey undertake biphasic movement (orientation followed by directed movement) that intersected with bathymetric contours towards shallower water. The coastal arrays captured movement under two larval odor conditions, a known habitat selection cue: low larval odor following lampricide treatment of the river, and higher larval odor from one year of larval recruitment plus the addition of putative synthesized larval odor components. Encounter with the river plume triggers an edge-mediated search behavior in the vicinity of the river mouth, whereas larval odor appears to only mediate the decision to enter. We address implications for control in the Great Lakes and conservation worldwide.