This report discusses the negative and positive aspects of aquaculture as an alternative to harvesting wild stocks of fish. The report defines aquaculture and describes its recent growth, as well as its ecological impact. Practices to sustain aquaculture operations, such as habitat modification and the use of wild-caught seedstock are discussed. Changes to ocean food webs, the introduction of non-native fish and pathogens, and nutrient pollution from wastes are presented as negative consequences of aquaculture operations. The report discusses strategies to improve aquaculture, such as reducing fish meal and oil in fish feed, integrating production systems, and promoting sustainability within the industry. Issues in Ecology is an ongoing series of reports designed to present major ecological issues in an easy-to-read manner. This Issue summarizes the consensus of a panel of scientific experts based on the information that was current and available at the time of its publication in 2001.