Relative contributions of probiotics, culture water, and larval maturation to the hatchery-raised white seabass microbiome.

White seabass larvae are spawned from wild brood stock and raised in a hatchery in Carlsbad, California, for local stock enhancement. Microbial balance in these larval systems is typically monitored through selective, culture-based methods, but comprehensive microbial characterization and tracking using next generation sequencing tools has yet to be performed. In this study, the microbiome of larval white seabass and culture tank water was assessed under the varying parameters of probiotic treatment, live feed selection, and time. The factor that contributed most to microbiome variability was time, which is equivalent to development or maturation through the larval stage. Secondarily, the larval microbiome consistently differed from their surrounding culture water. Neither probiotic treatment with INVE Aquaculture Sanolife MIC nor substitution of Artemia with rotifers for the first feeding had a significant impact on larval or culture water microbiome. The probiotic treatment also had no effect on larval growth or survival, but beyond these metrics and microbial dynamics, no other outcomes were tested. Across all larval periods, the most dominant bacterial phyla in the fish were Pseudomonadota and Bacteroidota. Vibrio, a possible opportunist in larval rearing systems, peaked in larval fish during the early feeding stages and coincided with turbulence in bacterial alpha diversity. Tenacibaculum, another possible opportunist and potential pathogen, was initially overrepresented in the culture water, but became present in the larvae by 46 days after hatching. This study exemplifies the utility of characterizing microbial patterns in fish aquaculture. This can help identify vulnerable larval periods and bacterial species to be monitored in consecutive life stages.