Development of high-nutrient-dense, low-pollution diets and prediction of aquaculture wastes using biological approaches

Abstract As with agriculture, aquaculture is a biological conversion process of food into animal production, but it differs, from a waste management viewpoint, from animal farming. Firstly, prediction of feed intake and optimum level of feeding are difficult, hence feed waste contributes a relatively large proportion of total waste output in most operations. Secondly, collection of wastes, both solid waste and soluble or dissolved waste, is also very difficult and wastes are rapidly dispersed into the surrounding water. These factors create many problems which are generally unknown to other animal farming operations. However, sustainable aquaculture can be maintained through nutritional strategies for the management of aquaculture waste (NSMAW) by minimizing waste outputs from the source. The basic principles are formulation of high-nutrient-dense diets and development of efficient feeding systems based on energetic data. Monitoring and quantitation of waste output is also carried out indirectly using digestibility measurements and comparative carcass analyses. This is a biological and nutritional approach rather than a conventional chemical approach to effluent analyses. These latter are laborious, inaccurate and expensive. Recent high-nutrient-dense (“low-pollution”) diet formulations output less than 200 kg solid waste and less than 5 kg P per tonne fish produced, but achieving this reduction of waste output requires completely revised feeding standards based on an average 15 MJ DE/kg salmonid fish produced.