[ AQUACULTURE ] for farmed animals within the EU, which has not yet been obtained. The absence of official approval is probably the main reason why potential investors are still reluctant to invest their money in this type of protein production. The spectrum of possible substitutes for fishmeal in feed for aquaculture is broad and continues to grow. At present, concentrates, isolates, meals and oils from plants, mostly from agricultural production, are mainly used for feed production. Soybeans, barley, rice and peas, or even potato protein can be used, and organic waste from bioenergy and bioplastics production may soon be added. Unfortunately, the plant proteins lack important amino acids such as lysine, methionine, threonine and tryptophan. This deficiency can be remedied by extracts of seaweed and microalgae, but it is clear that none of these substances can on its own completely replace fishmeal. Fish species that feed primarily on animal protein in the wild need taurine as an essential nutrient. That is why this must also be present in aquaculture feed, which is difficult for agricultural raw materials because taurine does not occur in terrestrial plants, or at least has not yet been detected there. In this case, too, macro-algae can present a solution, as significant amounts of taurine have been detected in Laminaria, Undaria and Porphyra. Some types of algae even contain pigments (carotenoids, astaxanthin) that give salmon and other salmonids or ornamental koi the desired intense colouring
Fish feed requires the right mix of different ingredients Although the nutrient profiles of the alternatives differ from the composition of fishmeal they at
least go some way towards reducing our dependence on marine resources. Whereas in the past feed manufacturers simply used fishmeal and could be sure that the nutritional requirements of fish and crustaceans were covered, much greater effort today goes into trying to find the right mixture for every species at every age, and the right proportions of the used components in the
feed cocktail. This increases the demands on and the responsibility of feed researchers, who have to solve numerous problems at the same time. The composition of many of the alternative feedstuffs has to be modified and specially prepared in order to render them suitable for use in aquaculture at all. Some ingredients, especially vitamins and lipids, need to be stabilized in order to preserve them
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for at least a certain period of time. If they are stored in a dry or frozen state there is an increased risk of oxidation and loss of nutritional value. Other potential feedstuffs contain compounds that cannot be utilised by the digestive system of a fish species or are even harmful. If bioavailability is not guaranteed, nutritional deficiencies can occur even though the nutrient required is actually present in the
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