In search for protein sources: Evaluating an alternative to the traditional fish feed for Arctic charr (Salvelinus alpinus L.)

Traditional sources of protein in fish feed for salmonids, such as fishmeal, face sustainability problems. Therefore, ingredients not attractive for human consumption are increasingly being considered for the development of future feeds. However, it is uncertain how this alternative range of ingredients will affect fish growth, quality and consumer opinion. In this experimental study, we tested a new fish feed on Arctic charr, containing a protein mixture from the Baltic Sea and yeast, all ingredients unattractive for human consumption. This feed comprised of sprat (Sprattus sprattus) and herring (Clupea harengus), blue mussels (Mytilus edulis) and baker's yeast (Saccharomyces cerevisiae), in a ratio of three parts to the whole. Fish fed with this feed grew 11.5% less than the control group. The digestibility and microscopy analysis of the faeces suggested a lower digestibility of the test feed, presumably caused by the fish's inability to utilize the nutrients from the yeast cells. Consumers’ perceptions of the final product were evaluated through a sensory evaluation, indicating no differences in scores of fillet quality between the two treatments. Potential implications of these results are discussed in context of feed composition, quality and other factors including species biology and season, which are relevant topics in the discussions on feed sustainability. Statement of relevance Evaluating a feed mix unattractive for human consumption.