Evaluating the effect of population density on Cutthroat Trout and Brook Trout competitive behavior and energy expenditure

In western North America, invasive brook trout (Salvelinus fontinalis) displace native cutthroat trout (Oncorhynchus clarki) throughout their range. One factor that may play a role in why cutthroat trout are being so widely displaced is the population density at which brook trout occur. To assess the effects of population density, juvenile cutthroat and brook trout were held in a simulated stream aquarium and observed at three population densities. The fish were monitored with a closed-circuit camera array. Antagonistic behaviors were measured via focal animal sampling of each individual. Individual energy expenditure was assessed using Tracker software that tracked fishes’ movements in recorded video and estimated hourly energy expenditure using a velocity-based metabolic model. Antagonistic behaviors observed included lateral threats, frontal threats, charges, chases, and nips. These data will determine the relationship between population density and the behavioral or bioenergetic competitive advantages of brook trout and cutthroat trout