**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION.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 njohnson@usgs.gov or via phone at (989)734-4768 x 128. Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**

Behavioral and chemical investigations of lake trout pheromones

Nicholas Johnson¹, Tyler Buchinger², Ke Li² and Weiming Li²

¹USGS Hammond Bay Biological Station, 11188 Ray Road, Millersburg, MI 49759

²Michigan State University, Department of Fisheries and Wildlife, Room 13 Natural Resources Building, East Lansing, MI 48824

April 2016

ABSTRACT:

Lake trout are hypothesized to use olfactory cues during reproduction. Olfactory cues are critical for many fishes, and may offer new tools for restoration of lake trout populations in the Great Lakes. Our overarching goal was to evaluate the roles of conspecific odors during reproduction in lake trout. Specifically, our objectives were to 1) determine if fry feces of guide selection of suitable spawning sites, 2) determine which sex and maturities release odors that are attractive to spawning adults, 3) profile bile acids hypothesized to function as pheromones in lake trout, and 4) evaluate whether olfaction is critical for spawning site location in a wild population of lake trout. We found that 1) fry odors likely dissipate or degrade before adults return to spawning reefs, and fry odors did not attract lake trout to artificial spawning reefs, 2) odors released by juveniles, males, and females are attractive to conspecifics, and likely function to guide aggregation, mate search, and spawning synchronization, and 3) release of taurocholic acid (TCA) and taurochenodeoxycholic acid (TCDCA) is restricted to males and juveniles, indicating bile acids may function as male mating pheromones in lake trout, and 4) lake trout can locate spawning reefs without olfactory cues, suggesting that the importance of olfactory cues and non-olfactory cues is likely context dependent. Taken together, our results indicate several pheromones, partially comprised of bile acids, likely guide reproductive behaviors in lake trout, but that other sensory modalities are also important. Continued research on lake trout olfaction may result in new management tactics that contribute to restoration of self-sustaining and genetically diverse lake trout populations in the Great lakes.