Dynamic Impacts of Stock Enhancement on Kaluga Sturgeon (Huso dauricus): Novel Conservation Strategy Insights from the Gut Microbe Composition and Gene Expression Mode.

The sturgeon population has experienced strict threats due to inordinate human activities in the last decade and has been classified into the Red List of Threatened Species in recent years. Stock enhancement is one effective practice for the conservation of wild sturgeons. However, the survival conditions for sturgeon were not satisfactory after they were directly restocked into their natural habitat. Huso dauricus is an important protected sturgeon species, and finding an appropriate conservation strategy for the wild population is urgent. To clarify the dynamic adaptability of Huso dauricus to its wild environment, 1000 individuals were released into a natural river. On the 0th, 7th, 14th, and 30th days, five recaptured individuals were used to evaluate the dynamic trends in biochemical biomarkers, intestinal histomorphology, gut microbe taxon composition, and transcription profile over 30 days of stock enhancement. Our results indicated that Huso dauricus individuals still had a physiological stress status on the seventh day and then gradually adapted to the wild habitat 14 days after reintroduction based on the serum cortisol level. Meanwhile, the feeding habitat, organ function indicators, and growth performance showed similar dynamic changes within 30 days. Interestingly, their gut bacterial diversity and taxon structure also fluctuated over the 30 days after restocking, and they were accompanied by dynamic changes in intestinal pathological injury and tight junction protein expression in this period. The transcriptome analysis revealed the dynamic adaptability of Huso dauricus to wild habitats associated with the expression modes of genes related to the FoxO family, immune system, cytochrome family, and ATP metabolism. Taken together, the findings of the present research demonstrated that artificial reintroduction had dynamic impacts on the health condition of Huso dauricus and that 14 days of wilderness training might be essential for sturgeon restocking practices. Our study revealed the adaption mechanism of Huso dauricus at the molecular level during the restocking period and shed light on the theoretical guidelines for wild sturgeon conservation.