Effects of low temperature on intestinal microbiota composition of silver pomfret (Pampus argenteus)

Fish are poikilothermic organisms with species-specific optimal temperature ranges for survival. As an economically important marine fish in China, silver pomfret (Pampus argenteus) has overcome artificial breeding bottlenecks. To meet aquaculture requirements in northern regions, we simulated gradual winter cooling from 18 °C to 6 °C using recirculating aquaculture systems with precision temperature control. Through histological sectioning, 16S rRNA gene sequencing, and ecological community assembly modeling, we found that feeding activity in silver pomfret is positively correlated with water temperature, exhibiting a significant decrease with declining thermal conditions. Concurrently, intestinal structural alterations were observed, including diminished collagen staining, enlarged intercellular spaces, and reduced fold height. The microbial diversity initially decreased and subsequently increased during the cooling process. The microbial community was influenced by variable selection and dispersal limitation. At the onset of the cooling period, Vibrio emerged as the dominant genus; however, after prolonged exposure to low-temperature stress, Pseudoalteromonas, Pseudomonas, and Shewanella became predominant genera. Under low temperature conditions, metabolism-related pathways are activated. This study provides new insights into mechanisms underlying low-temperature adaptation and supports silver pomfret breeding at reduced temperatures.