Predominant gut microbiota in the early life stages of red seabream (Pagrus major) raised in indoor tanks

This study was performed to assess, by molecular methods, the gut microbial community associated with early life stages of the reared red seabream (Pagrus major). This work sought to better understand the gut microbiota during seed production, which may help control disease in the near future. At the larval fish stage, Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria (excluding Vibrionaceae) were predominant in fish guts. These bacteria also predominated in rotifers, the primary component of the larval fish diet. At the juvenile stage, Gammaproteobacteria, Alphaproteobacteria, and Flavobacteria (except for Flavobacteria in one of two juvenile libraries) were predominantly detected in fish guts. Again, these bacteria also predominated in Artemia nauplii, a main component of the juvenile fish diet. These results suggested that the gut microbiota of larval and juvenile red seabream is influenced primarily by the microbiota of their diets. On the other hand, members of the family Vibrionaceae were not detected in larval fish guts, the rearing seawater, or rotifers, whereas bacteria of this family represented 28.6–64.6% of the reads in two libraries of juvenile fish guts. These observations suggested that hygiene management and administration of probiotics at the early life stage of red seabream are effective in suppressing the onset of opportunistic infections.