This thesis examined the chemical constituents of repellent odors in the sea lamprey (Petromyzon marinus), an invasive fish in the Great Lakes basin, for use in management and conservation. Odors are powerful tools that guide organism's movement decisions, and repellent odors such as conspecific alarm cues are particularly potent. In chapter one, we investigated the chemistry of the alarm cue through behaviorally guided fractionation. We found substantial avoidance responses to two major fractions: water-soluble and chloroform soluble and a full avoidance response upon recombination of the two fractions. We found no consistent avoidance patterns to subfractions, or individual compounds identified in the water-soluble fraction, and we found no avoidance response to all 32 identified compounds from the water-soluble fraction when combined at observed ratios in the skin. In chapter two, we investigated the role of a potential repellent molecule, putrescine, on sea lamprey activity and avoidance in a small individual behavioral assay and avoidance in a large, multi-animal assay. We found a context-dependent response, where sea lamprey did not increase activity in the small assay but did show a substantial avoidance response to putrescine. No evidence of avoidance to putrescine was observed in the large assay. In sum, these results suggest the alarm cue is likely not contained in the 32 identified compounds in the water-soluble-fraction alone and that the behavioral response to putrescine is context dependent. While elucidating the chemistry of the sea lamprey alarm cue may be more difficult than through behaviorally guided fractionation alone, the continued pursuit is worthwhile because of the utility in invasive species management and conservation of native species.
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