Transition from clear-water to biofloc systems improves growth, antioxidant response, and gene expression in Penaeus vannamei

Integrated aquaculture systems that combine biofloc technology (BFT) with recirculating clear-water (CW) environments have attracted increasing interest. This study investigated the effects of transitioning from a CW to a BFT system on culture performance of Penaeus vannamei. Two culture models were tested: a single CW system (SCW) and a CW to BFT transition system (TBI). Over the 50-day experiment, TBI maintained lower ammonia and nitrite concentrations than SCW. Gill histology revealed no overt necrosis or structural damage in either treatment group. TBI achieved a higher yield (2.79 kg/m³) and survival (96.5 %) than SCW (P < 0.05). The results of antioxidant enzyme analysis indicated improved oxidative status in TBI, and lower malondialdehyde (MDA) levels relative to SCW (P < 0.05). Transcriptome analysis showed that bioflocs may produce some “stimulation” to shrimp, which increases immunity and improves adaptability to the environment. Additionally, Energy metabolism also appeared elevated in TBI, reflected by higher Na⁺-K⁺-ATPase and total ATPase activities and the upregulation of ATP-linked and glycogen-biosynthesis genes. However, the total suspended solids (TSS) exceeded 600 mg/L late in culture period, which may have influenced physiological responses. Overall, the CW to BFT transition was associated with enhanced stress resistance, immune status, and energy metabolism, as well as improved growth performance and culture efficiency.