Sofia Afoncheva

Copepod culture as the basis for sustainable fish production

A lot of potentially valuable species of fish are not yet being successfully cultured due to challenges in finding the appropriate feed for fish larvae after hatching. Larvae of marine fishes require live feed for successful development and growth. Copepods showed to be the optimal nutrient source for larvae. Copepods nutritional quality is defined by the composition and abundance of fatty acids (FA), especially by the polyunsaturated ones (PUFA).

My PhD project is focused on investigating the relationship between the changes of biochemical composition of copepods’ diets (microalgae, yeasts or alternative diets) and copepods’ nutritional quality as live food for marine fish larvae. I aim to achieve high nutritional quality copepods through manipulation of FA composition in their diets. Various diets, consisting of microalgae, differed in FA profiles, and yeasts will be offered to copepods. FA profiles of copepods and algae will be compared afterwards in order to identify the optimal diet. Copepods with the highest content of PUFAs will be offered to fish larvae. The effect of with microalgae enriched copepods on fish larvae performance will be evaluated through investigation of larval health status, growth, survival and stress resistance.

It is known, that some species of copepods are able to synthesize PUFA de novo. Therefore, especially interesting will be to determine the conditions that induce production and/or accumulation of PUFAs in copepods and to identify copepod species that possess the highest ability to biosynthesis. PUFA-rich and PUFA-poor diet can promote or inhibit production of FA in copepods. Experiments with copepods, feeding on diets, differed in PUFA contents and in their precursors, can help to reveal the mechanism of FA biosynthesis. Determining the conditions that stimulate biosynthesis or promote to switch from accumulation to biosynthesis is one of the most challenging parts of my project.