Towards effective nutritional management of waste outputs in aquaculture, with particular reference to salmonid aquaculture operations

Long-term sustainability of many fish culture operations may be dependent on their ability to reduce their waste outputs. The release of solid wastes is mainly a function of the digestibility of various dietary components, and the release of dissolved wastes is mainly a function of the metabolism of nutrients by the fish. Consequently, simple principles of nutrition and models have been effectively used to describe, predict and manage the excretion of wastes by fish. Nutritional strategies offer a direct and effective way of managing waste output by aquaculture operations. Very significant reduction in waste outputs per unit of fish produced, notably in terms for solid and phosphorus wastes, have been achieved over the past few decades by commercial fish culture operations. Further reduction in waste outputs could be achieved through fine-tuning of feed formulations, judicious use of feed additives and processing/refining of ingredients. A better understanding of the basis of the effect of various endogenous (biological) and exogenous (dietary, environmental) factors on nutrient utilization by fish could also contribute to the development of strategies for reducing waste outputs. The present paper provides a brief overview of issues and challenges related to potential environmental impacts of wastes, and of recent progresses relative to nutritional strategies aimed at better management of the release of wastes by aquaculture operations.