DEVELOPMENT OF HIGH-NUTRIENT-DENSE, LOW-POLLUTION DIETS AND PREDICTION OF AQUACULTURE WASTES USING BIOLOGICAL APPROACHES

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 diss olved waste, is also very difficult and wastes are rapidly dispersed i nto the surrounding water. These factors create many problems which ar e generally unknown to other animal farming operations. However, susta inable aquaculture can be maintained through nutritional strategies fo r the management of aquaculture waste (NSMAW) by minimizing waste outp uts from the source. The basic principles are formulation of high-nutr ient-dense diets and development of efficient feeding systems based on energetic data. Monitoring and quantitation of waste output is also c arried out indirectly using digestibility measurements and comparative carcass analyses. This is a biological and nutritional approach rathe r than a conventional chemical approach to effluent analyses. These la tter are laborious, inaccurate and expensive. Recent high-nutrient-den se (''low-pollution'') diet formulations output less than 200 kg solid waste and less than 5 kg P per tonne fish produced, but achieving thi s reduction of waste output requires completely revised feeding standa rds based on an average 1 5 MJ DE/kg salmonid fish produced.