Cage aquaculture in hydroelectric reservoirs has great potential for expansion in Brazil, but there are concerns of negative environmental impacts. The environmental sustainability of cage culture depends on hamornization between farming practices and the hydrological peculiarities of the site. Mass balance modeling can estimate the amounts of nutrients that can be loaded without triggering eutrophication and resulting maximum allowable production volume. Careful climate zoning can also assist proper siting.Universidade Estadual Paulista, Departamento de Morfologia, Instituto de Biociências de BotucatuUniversidade Estadual Paulista, Departamento de Parasitologia, Instituto de Biociências de BotucatuUniversidade Estadual Paulista, Departamento de Biologia e Zootecnia, Faculdade de Engenharia de Ilha Solteira