Governments and the private sector must often make decisions based on incomplete knowledge and a high degree of uncertainty and where such decisions may have farreaching social, environmental and economic consequences. Risk analysis is a process that provides a flexible framework within which the risks of adverse consequences resulting from a course of action can be evaluated in a systematic science-based manner. It permits a defendable decision to be made on whether a particular risk is acceptable or not, and the means to evaluate possible ways to reduce a risk from an unacceptable level to one that is acceptable. Risk analysis is now widely applied in many fields, for example, in decisions about risks due to chemical and physical stressors (natural disasters, climate change, contaminants in food and water, pollution, etc.); biological stressors (human, plant and animal pathogens; plant and animal pests; invasive species, invasive genetic material); social and economic stressors (public security (including risk of terrorism), construction and engineering (building safety, fire safety, military applications), and business (project operations, insurance, litigation, credit, cost risk maintenance, etc.). The general framework for risk analysis consists of four major components: • Hazard identification – the process of identifying hazards that could potentially produce consequences. • Risk assessment – the process of evaluating the likelihood that a potential hazard will be realized and estimating the biological, social and/or economic consequences of its realization. • Risk management – the seeking of means to reduce either the likelihood or the consequences of it going wrong; and • Risk communication – the process by which stakeholders are consulted, information and opinions gathered and risk analysis results and management measures communicated. Some basic principles that appear to be common to all types of risk analysis include those of common sense, uncertainty, precaution, objectivity, transparency, consistency, scientific validation, stakeholder consultation, stringency, minimal risk management, unacceptable risk and equivalence. Understanding and applying risk analysis in aquaculture 4 Risk analysis has wide applicability to aquaculture. It has mainly been applied in assessing risks to society and the environment posed by hazards created by or associated with aquaculture development. These include the risks of environmental degradation; introduction and spread of pathogens, pests and invasive species; genetic impacts; unsafe foods; and negative social and economic impacts. The use of risk analysis can provide insights and assist in making decisions that will help to avoid such negative impacts, thus helping aquaculture development to proceed in a more socially and environmentally responsible manner. Risk analysis is less commonly used to achieve successful and sustainable aquaculture by assessing the risks to aquaculture posed by the physical, social and economic environment in which it takes place. These include reduction of environmental risks (e.g. due to poor siting or severe weather events), biological risks (infection by pathogens via transfer from native stocks, predation by seals and sharks; red tides, etc.), operational risks (poor planning, work-related injuries), financial risks (e.g. market changes, currency fluctuations, emergence of new competitors, etc.) and social risks (negative image and resulting product boycott, lack of skilled manpower, competition from other sectors).