We studied effects of chum salmon spawning activities on nutrients, epilithic algae, and benthic insect communities in a small stream of Pacific Northwest. The reach with salmon spawning had greater concentrations of Kjeldahl-N, NH4+-N, and total soluble P than the reach without salmon. However, chlorophyll a concentration was lower in the reach with salmon. In particular, chlorophyll a concentration was significantly lower during salmon spawning. Three caddisfly genera and two stonefly genera collected from salmon carcasses fed on salmon flesh. The total insect density in containers baited with salmon flesh was significantly greater than in containers without salmon flesh, but the difference was insignificant for the total biomass. Orthocladiinae andBaetissp. had significantly greater densities and biomasses in the containers with salmon flesh. These results support the notion that mass salmon spawning activities affect structure and dynamics of ecosystems.