The growth of the fish industry, as a result of the development of aquaculture, requires specific knowledge on nutritional requirements of cultured fish and shellfish species. These requirements can be influenced by factors as diverse as fish size, feed composition, feeding practices, system management, as well as by the statistical and mathematical tools utilized in the analysis of fish nutritional research data. This paper presents a critical appraisal on the use of the 'broken-line' model in the analysis of growth data derived from a dietary protein requirement assay with 'tambaqui' (Colossoma macropomun). Results show that the 'broken-line model analysis', as performed by a linear regression procedure, is simple, fast and reliable, suitable for the analysis of fish growth data. Nevertheless, the model may underestimate values determined by other methods, which may or not have higher precision levels.
'broken line analysis'; nutritional requirement; fish
