Optimizing intensive shrimp production: Relieve the physiological pressure in Penaeus vannamei through transition from biofloc technology to recirculating clear-water aquaculture systems

Abstract

Biofloc technology systems (BFTs) and recirculating clear-water aquaculture systems (RCWs) are widely used engineering approaches for intensive shrimp culture. To improve practical performance, this study evaluated a time-sequenced retrofit that transitions from BFTs to RCWs (TCW) against a baseline, zero-exchange BFTs operated under conventional routines (SBI). The TCW regime was divided into two stages: BFTs were employed from days 0–30, followed by RCWs from days 30–50. During the second stage, TCW maintained total suspended solids (TSS) below 40 mg/L, whereas TSS in SBI rose to 683.33 mg/L and exceeded the commonly recommended range only at termination. Shrimp in the TCW exhibited healthier gill morphology and significantly lower malondialdehyde (MDA) levels (p-value < 0.05), indicating reduced oxidative stress Activities of Na⁺ /K⁺-ATPase and ATPase in TCW showed an increasing trend, consistent with improved osmoregulatory function. Transcriptomic analysis revealed upregulation of immune-related pathways (e.g., extracellular region, hemolymph coagulation, innate immunity) in SBI, accompanied by enhanced expression of cell cycle genes involved in DNA repair and proliferation. However, genes related to molting, protein glycosylation, and metabolic homeostasis were predominantly downregulated, indicating energy was diverted toward immune defense. In contrast, nitrogen metabolism pathways were upregulated in TCW, supporting improved ammonia detoxification and energy allocation toward growth. Together with significantly higher weight gain rate and specific growth rate (p-value < 0.05), these findings indicate that a BFTs to RCWs transition reduces physiological stress and improves metabolic efficiency. This staged design provides a practical reference for optimizing shrimp farming systems and promoting sustainable aquaculture.