Initial diet influences future development paths of gut microbiota in larval northern pike (Esox lucius)

Diet plays a critical role in the composition and development of the gut microbiome and benefits of a healthy gut microbiome are well understood in humans; similar symbiotic functions likely exist in fish. We examined the link between northern pike ( Esox lucius ) initial diet and gut microbiome during the first 4 weeks of fish development by manipulating feed type and characterizing microbial communities of fish guts, water, and diet samples via next generation sequencing of the 16s rRNA gene. Swim-up fry received one of two ‘initial’ diets ( Artemia sp. or zooplankton) for 2 weeks before transitioning to a dry pellet diet. We observed differences in gut microbiota between diet treatments and within treatments across time. In particular, differences were detected between weeks three and four in Artemia sp. and zooplankton treated fish despite transition to a dry pellet diet. Late sampled fish (weeks 3 and 4) exhibited a pattern of decreased microbial diversity compared to fish from weeks 1 and 2. Despite fish being shifted to the same diet, these divergent paths indicate a strong influence of initial diet on gut microbiome structure later in life. Overall, diet showed a deterministic influence on the presence/absence of certain bacteria in the fish gut microbiome.