Current fishing practices are regarded as unsustainable (Pauly et al. 2002), yet our appetite for seafood grows. To meet the growing gap, there are increasing calls for mankind to tame the oceans through aquaculture (Marra 2005). Close to the coast, rapid expansion of marine aquaculture is underway throughout the world. Sea cages enclose 2.5 million tons of fish, while 12 million tons of mussels, oysters and clams hang from floating ropes or grow on racks or trays (FAO 2004). Aquaculture structures are now ubiquitous to many coastlines. As the expansion continues, how can we best manage the interaction between natural communities and aquaculture?