GutEngFish aims to support mariculture by enhancing the metabolic potential of the gut microbiota in farmed fish to improve growth and feed efficiency. The interaction between diet and gut microbiota has gained importance with the increasing use of sustainable alternatives in aquafeeds. Fish-derived components are often reduced to below 20% of formulations by incorporating plant-based, insect, and algal ingredients. As these ingredients differ from the natural diet of carnivorous marine fish, such changes can impair gut function, reduce nutrient utilisation, alter microbiota composition, and compromise product quality.

GutEngFish will test a new approach: using the gut microbiome of a wild herbivorous fish (salema) to “train” the gut of seabream to process more plant ingredients. Faecal microbial transfer (FMT) is advantageous because it transfers an entire, diverse, and functionally redundant microbial community that can support gut balance more effectively than one or a few probiotic strains. We will transfer gut microbes from salema to seabream, monitor safety, and assess effects on growth, health, and fillet quality in a controlled trial. FMT will help identify key beneficial microbes and functions, which can later be combined into defined microbial mixtures or consortia-type probiotic-like products, supporting more sustainable Adriatic mariculture and the circular bioeconomy.

Funded by Croatian Science Foundation