Understanding factors that influence variation in species interactions is important for predicting the impact of disruptors to communities, such as invasive species. Benthic primary production is one factor likely to influence consumer-resource interactions given that grazing impacts can be larger and primary consumer densities are often higher in productive areas.  The New Zealand mud snail, Potamopyrgus antipodarum, an exotic in the western U.S., dominates macroinvertebrate communities in some streams, but densities vary widely in other areas.  In field experiments across 9 streams, we tested the hypothesis that this invasive snail has larger grazing effects and reproduces earlier in more productive streams.  Using in-stream cages with and without snails, we examined the response of periphyton to snail grazing and measured snail size at first reproduction.  We found that in the most productive streams, Potamopyrgus decreased overall algal standing stocks, and to a lesser extent, gross primary production.  Snails also reproduced earlier in the most productive streams.  Together, these results suggest that highly productive streams experience the largest grazing effects and also support fast-growing populations of Potamopyrgus, eventually leading to greater overall impacts on native stream communities in productive habitats.