Brook Trout Foraging Behavior: A Combined Field and Laboratory Study Investigating Aquatic Versus Terrestrial Prey Selection

Brook trout (Salvelinus fontinalis) seemingly operate in violation of optimal foraging theory as indicated by previous research in that brook trout appear to feed preferential upon aquatic benthic invertebrates even in situations when terrestrial invertebrates have higher energy content and accessibility. This has led us to develop the hypothesis that brook trout prefer aquatic invertebrates to terrestrial invertebrates when ample amounts of both prey types are present; when aquatic production is low, brook trout switch to a more opportunistic feeding behavior resulting in higher amounts of terrestrial invertebrates present in their diets. A combined field and laboratory study was designed to test this. The field component compared kick net and stomach contents samples collected across two seasons and four head-water streams. The results of this study ultimately sculpted the variables tested in the laboratory experiment. Specifically, can location in water column along with prey type and life stage dictate prey selection? Perhaps it is simply starvation versus satiation that motivate brook trout to forage one prey type over another. Results of this study will be discussed and can give insight to the persistence of brook trout populations in an ever-changing immediate environment and changing subsidies from the adjacent terrestrial ecosystem.