Population structure, diet, and bioenergetics of introduced Smallmouth Bass in an Intermountain West reservoir

Smallmouth Bass Micropterus dolomieu is a recreationally important sport fish throughout much of North America, but population metrics are lacking in the Intermountain West, where the species is not native and where its performance may differ from other geographic portions of its range. We characterized population structure and condition, growth, and the feeding habitats and bioenergetics of a self-sustaining Smallmouth Bass population in Starvation Reservoir, located in northeast Utah. In this reservoir, Smallmouth Bass may experience environmental conditions (e.g., shorter growing season and greater water-level fluctuation) that are uncommon to other portions of its range. We found growth rates to be intermediate within the context of surveyed populations across its distribution, with fish reaching quality length (280 mm TL) at approximately age 4 and relative growth index values ranging from 86 to 112 for fish ages 2-10. Fish condition (relative weight) was at or above average across all size classifications encountered (stock, quality, preferred, and memorable), and diet analyses indicated that fish used a variety of prey types that differed by season. Bioenergetics models indicated that proportional feeding was highest for age-2 fish (P = 0.54) and declined incrementally through age class, relating to trends of relative growth. Our results suggest that the Smallmouth Bass population in Starvation Reservoir is performing well within the constraints of a midelevation, Intermountain West reservoir. Our study may provide managers with useful data to compare with other Smallmouth Bass populations in this geographic region.