No one can be involved in aquaculture for very long without becoming aware of the extensive array of legislation within which the industry operates in Europe1. At the farm level, it may sometimes feel as if the legislation is a brake on development at a time when aquaculture is regularly proclaimed as the fastestgrowing food sector in the world. Are aquaculture producers in Europe to be disadvantaged in playing their part in the development of the industry, and from enjoying their share of the prizes? This would be of no benefit, and seems unlikely as a policy goal. Why would policy and its organising legislative framework conspire to disadvantage Europe in this regard? Yet at the operational level, the legislative net seems to tighten, and the associated costs of compliance to rise, in a sector where margins are already hard to maintain. The AQUAETREAT project was conceived in part as a response to such strengthening environmental legislation, at a time when its current and future impact on aquaculture was becoming increasingly apparent. How to reposition production operations to comply with more stringent environmental requirements, at the same time as achieving the improvements in efficiency necessary to remain viable? Legislation is not the only force shaping the industry. Technological development is playing a critical role in mediating the twin goals of increasing efficiency and compliance. Later chapters focus on technological aspects of development.