Matching Watershed and Otolith Microchemistry to Establish Natal Origin of an Endangered Lake Sucker

Anthropogenic changes to the landscape of the western U.S. have resulted in high rates of decline in freshwater species, and like many endemic desert fish, the June Sucker (Chasmistes liorus) is endangered.  Implicit within the recovery plan, spawning habitat restoration must result in natural recruitment.  We used otolith microchemistry to establish natal origins of the potamodromous June Sucker to evaluate effectiveness of tributary habitat restoration.  Our specific objectives included: 1) quantifying and characterizing the extent of chemical variation among spawning tributaries; 2) determining the relationship between otolith microchemistry and tributary chemistry and; 3) developing and validating a classification model to identify stream origin.  Water chemistry differed significantly among tributaries.  We observed a strong linear relationship between water and otolith microchemistry for Sr:Ca and Ba:Ca, but not for Mg:Ca.  The classification models accurately classified individual fish to their natal tributary (classification tree 89%; random forest model 91%), and could determine if the fish’s origin was wild vs. hatchery with 100% accuracy.  Overall, this study will aid in evaluating the effectiveness of restoration and tracking progress toward recovery for the June Sucker in Utah Lake, and can be applied to other imperiled systems with species of conservation concern.