Population Dynamics of Yellowstone Cutthroat Trout in Henrys Lake, Idaho

Abstract Yellowstone Cutthroat Trout (YCT) Oncorhynchus clarkii bouvieri is a species with significant ecological and recreational value. In many YCT fisheries, managers are tasked balancing angler expectations fish conservation. Henrys Lake supports popular trophy trout fishery, but the increase of nonnative Utah Chub Gila atraria has caused concern for YCT. We summarized long-term trends in abundance, length structure, body condition, growth to evaluate effect Chub. Additionally, we investigated abiotic biotic factors influencing examined archived hard structures provide comprehensive evaluation changes age system. used stocking records catch rates as covariates explain growth. Catch varied from 1.5 15.4 per net night during 2002 2020 sampling period, did not identify consistent patterns. Length structure was consistently dominated by stock- quality-length fish, captured few >600 mm total length. Relative weight decreased mean ± standard deviation (SD) 115.9 16.5 2004 93.2 8.2 2020. The between 1 11 years; that 2010 were oldest. majority sampled 4 younger. Total annual mortality age-2 older higher than other populations (i.e., 0.70 0.60 2011 2020). Based on regression models, identified positive relationships YCT, Brook Salvelinus fontinalis, Rainbow mykiss × hybrid trout. observed negative abundance Trout. Although relationships, recent decades fast or faster earlier time periods. Results this research suggest major population dynamics evident over last 20 years. This study provides insight into an adfluvial population. particular, results may be useful systems where have been introduced.