- Mette Sørensen, Professor, FBA, Nord University
- Oddvar Ottesen, Professor, FBA, Nord University

About the thesis:
Spotted wolffish is a promising candidate for cold-water aquaculture production. There is a knowledge gap of its capacity to utilize modern diets.  Fishmeal and -oil have been the main ingredients used to feed farmed fish in the past. Growth of aquaculture production has to take place without dependence of fishmeal and fish oil. The current solution is to use plant ingredients, however, it is also expected that use of single cell organisms will increase in the future, such as microalgae.

There are not much information about the potential of wolfish to utilize plant ingredients or microalgae in feed. Microalgae may have a potential as feed ingredient for wolfish due to their high levels of protein with balanced amino acid profiles and content of essential fatty acids, antioxidants and vitamins.

In this PhD project we evaluated incorporation of microalgae in diets for juvenile spotted wolffish in two experiments. The first experiment evaluated replacement of fishmeal with graded levels of the microalgae Scenedesmus obliquus. The second experiment evaluated replacement of a mix of fish- and plant-based ingredients with the microalgae Nannochloropsis oceanica. In both experiments, the fish had comparable growth rates to what has previously been reported for wolffish of similar size. Changes in fatty acid composition, muscle growth and chemical composition as well as in the proteome of liver, muscle and intestine of the fish was observed when the fish was fed microalgae in the feed.

The results of this thesis suggests that spotted wolffish show a promising potential for tolerating microalgae in the diet and that moderate inclusion levels (around 15%) of microalgae in the diet may have beneficial effects on fatty acid composition of the fish and potentially also muscle growth, fish health and antioxidant capacity.