Date of Award

Spring 2022


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Document Type


Degree Name

Master of Science (MS) in Biology




The goal of this study was to determine which olfactory cues were most attractive to Westslope Cutthroat Trout Oncorhynchus clarkii lewisi (WCT) in a two-choice Y-maze. WCT used in this study were from Kings Lake and Paqua Creek in Pend Oreille County, Washington, and tested in 2018 and 2019. The different odorants tested in this study were population-specific pheromones produced by WCT from the same population, conspecific pheromones produced by WCT from the second population, and water obtained from each population’s natal stream. The water Kings Lake WCT were reared in for one year at the Spokane Hatchery was also used. A meta-regression was used to determine if WCT preferred an arm in the Y-maze when no odor was present, when one arm contained one odor, or when both arms were scented with an odor. WCT did not prefer either the left or right arm and selected the arms of the Y-maze randomly when only well water was supplied (P > 0.05). WCT exhibited a positive response when one arm of the Y-maze was scented with pheromones, natal stream water, or hatchery rearing water for Kings Lake WCT (P < 0.05) by selecting the arm with the odor over the arm with well water only. When both arms of the Y-maze contained an odor, WCT were unable to differentiate and select an odor. There were no significant differences found between the proportion of time WCT spent in either arm for the population-specific versus conspecific odors (P > 0.05), hatchery rearing water versus natal stream water for Kings Lake WCT (P > 0.05), and population-specific pheromones versus natal stream water for Paqua Creek WCT. In summary, WCT could detect pheromones from other WCT, odors from their natal stream and rearing water, but WCT might not be able to differentiate between population-specific or conspecific pheromones. Understanding the cues WCT use for upstream migration can illuminate why continuous migrational routes are paramount for salmonid migrations and help prioritize resources to be used for conserving and ensuring the ability for WCT to follow their olfactory cues.