Traditionally, fish feed consists of fish meal and fish oil, especially for carnivorous fish such as eels, salmon and trout. However, while demand is increasing, the availability of fish meal and fish oil is decreasing. Because these fish mainly eat other types of fish their diet by nature has little fibre or carbohydrate and so they are not able to properly digest these. Their major source of energy is fat, which they store in their fatty tissues. Protein is necessary for (muscle) tissue structure.
The required proteins and fats can be partly derived from plant sources. Plant proteins are able to replace the necessary proteins in fish feed for up to 50%, without any consequences for growth.