Gut microbiota of farmed Atlantic cod

Farmed aquaculture has the potential to meet consumer demand and ease pressure on wild resources for carnivorous fish such as Atlantic cod (Gadus morhua) where wild stocks are in decline or at risk. Cod farming has yet to be widely adopted by the aquaculture industry with cited issues including high mortality and bacterial infections. In addition to the economic cost of fishmeal (FM), a practice that in of itself is environmentally and economically unsustainable. There is little knowledge on how alternative FM replacements or supplements affect cod health and the gut microbiota is poorly characterised. Therefore, the objective of this study was to supplement the diet of juvenile Atlantic cod with 10% macroalgae (egg wrack Ascophyllum nodosum or sea lettuce Ulva rigida or a control FM diet and to determine the effects on fish health (growth, condition factor K), gut health (physiological analysis of gut tissue and internal organs) and gut microbiota composition (16S rRNA amplicon sequencing) in a 12-week trial.