Fishes have driven the evolution and ecology of reef ecosystems for over 200 million years and today, fishes are the strongest link between humans and coral reefs. This presentation will (i) explore the importance of fishes in shaping the evolution of marine ecosystems, especially coral reefs, (ii) examine the critical roles of fishes in maintaining ecosystem processes, and (iii) discuss how fishes reveal the nature and impacts of human activity on coral reefs and in other ecosystems. The overarching goal of my research has been to develop a picture of coral reefs as functional ecosystems. The approach has enabled us to examine changes over evolutionary timescales, looking at how reefs operated rather than simply documenting changes in diversity through time. More importantly, this functional approach also provides insights into the critical importance of fishes in maintaining key processes on modern coral reefs. By recognising these processes, we are able to understand how human activity is shaping the future of coral reefs and other aquatic ecosystems. Our capacity to modify fish populations, for example, can profoundly alter marine ecosystems. Yet if these changes are detected early and if appropriate measures are taken, our interactions with fishes may enable us to plan for positive outcomes in an increasingly uncertain future. Our ability to understand the importance of fishes, not only for humans, but also for marine ecosystems, will be critical for our future welfare. Once simply targets for the dinner plate, fishes may become one of our best allies when coping with environmental change.