Rivers and lakes are disproportionately rich in species, and worldwide degradation of these ecosystems jeopardizes both their biodiversity and their value to humanity for food, water, and recreation. Sound strategies are needed to guide conservation efforts from the local to global scale. Our work integrates perspectives on evolutionary diversification, ecological linkages between organisms and ecosystems, and environmental change to support scientific advances, successful restoration, and public engagement. Fish and fisheries are an especially compelling intersection between environmental quality and human interests. Our place-focused research at field sites around the world complements large-scale spatial analyses to yield interdisciplinary insights ranging from speciation rates to community stability to food security. Partnerships with resource management agencies and conservation non-profits provide a means of translating scientific insights into practical strategies for enhancing the sustainability of freshwater ecosystems.