Shifting precipitation patterns are altering foraging and growth potential for freshwater fishes across the globe. In Gulf of Alaska watersheds, increased frequency of extreme high flow-events, punctuated by longer duration summer low-flows, is likely to alter accessibility to small tributaries that deliver terrestrial prey subsidies to juvenile salmon and trout. Here, we investigate the impact of high and low flows on juvenile salmonids’ ability to exploit terrestrially derived food subsidies through changes in access to intermittent tributary habitats. Our research asks: what is the role of hydrologic variability and stream physical conditions in driving fish movement between mainstems and small tributaries? And how do patterns in habitat occupancy, diet, and movement behavior influence realized growth potential? Using paired PIT tag antenna arrays placed at the junctions of two mainstem-tributary confluences, we recorded the movement of more than 500 individual fish between habitats, while simultaneously tracking the diet and growth of tagged individuals displaying alternative habitat use strategies. We found that movement patterns occurred more often at higher levels of flow, when small tributaries were presumably more accessible and when fish in tributaries were able to capitalize on terrestrial invertebrate subsidies, especially earthworms. While past research has documented pulse subsidies to fish associated with high-flow events, we specifically consider spatial heterogeneity in resource availability, thermal regime, and tributary habitat access to develop a comprehensive understanding of spatial foraging strategies and the resulting impacts on realized growth. By identifying where and when fish move to maximize foraging potential in response to high- and low-flow events, we can better understand the implications of land management decisions that promote or restrict access to tributary habitats along stream networks.