Exploring the Potential for Biological Control of An Explosive Prey Base By a Suite of Three Predatory Fishes in a Western Reservoir

In reservoirs, the spread of introduced species into artificial species assemblages may alter trophic interactions in ways difficult to predict, thus offering excellent opportunities to explore food web dynamics, but also challenging fisheries management.  In a high elevation reservoir, UT, the unintentional introduction of Utah chub and subsequent population expansion prompted managers to shift from stocking exclusively rainbow trout, to include tiger and cutthroat trout as potential biological controls.  We initiated a multi-faceted study of field observations and bioenergetic simulations to investigate predator interspecific interactions and quantify predator demand versus prey supply.  Our results suggest a substantial portion (20%) of chub outgrow predator gape limits; chub >250 mm in length are not susceptible to predation.  Furthermore, considerable trophic niche overlap suggests substantial potential for competition.  Large cutthroat and tiger trout occupy a piscivorous trophic niche, whereas rainbow trout trophic niche space is omnivorous, overlapping with chub.  Moreover, rainbow trout CPUE has declined significantly in recent years, potentially due to competition for shared food resources or preferred littoral feeding space.  Collectively, this research will aid managers in designing and implementing the best stocking strategy to optimize sport fish performance, control chub, and enhance and maintain angler satisfaction.