In general, carnivorous species have a limited ability to utilise starch and no capacity to digest non-starch polysaccharides. Plant materials, which are used as alternative sources of protein instead of fishmeal, will inevitably contain significant amounts of carbohydrates, predominantly in the form of non-starch polysaccharides and starch. Feeding plant materials to fish in aquaculture will be most efficient (less expensive) if the carbohydrate material is utilised.