A land-based tank aquaculture system coupled with effluent treatment ponds: Effect of stocking density on the growth performance of gibel carp (Carassius gibelio)

Recirculating aquaculture systems (RASs) are recognized for their eco-friendly and efficient approach in aquaculture. This study constructed a novel system: a land-based tank aquaculture system coupled with effluent treatment ponds (LBTAS). The system includes land-based tanks, an oxygen supply system, a water inlet system, a sewage collection system, and an effluent treatment system. We evaluated the impact of different stocking densities on the growth, health, aquaculture yield, and economic benefits of gibel carp ( Carassius gibelio ) in the LBTAS. The yields of the high stocking density (HSD) group and the low stocking density (LSD) group were similar, which was more than three times that of traditional pond farming. But the LSD group significantly improved final weight (FW), final length (FL), weight gain ratio (WGR), specific growth rate (SGR), feed conversion ratio (FCR), ingestion rate (IR), and viscerosomatic index (VSI) compared to HSD groups ( P ​< ​0.05). While survival rates and the hepatosomatic index (HSI) were similar across groups, the low-density group exhibited better overall health. Serum biochemical indicators such as glucose (GLU), cholesterol (CHO), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) were unaffected by density. However, levels of alanine aminotransferase (ALT), triglycerides (TG), lactate acid (LD), and cortisol were significantly higher in the HSD group ( P ​< ​0.05), indicating increased stress. Hepatic antioxidant analysis showed stable levels of glutathione peroxidase (GSH-PX) and total superoxide dismutase (T-SOD), but higher levels of catalase (CAT) and malondialdehyde (MDA) in the high-density group (P ​< ​0.05), suggesting increased oxidative stress. Muscle histology analysis revealed significantly higher muscle fiber density in the LSD group ( P ​< ​0.05), with no significant effect on muscle fiber diameter. Water quality analysis indicated poorer quality in the HSD group, with lower dissolved oxygen and significantly higher concentrations of total phosphorus (TP) and nitrite nitrogen (NO 2 − -N) compared to the LSD group ( P ​< ​0.05). Despite the initial lower cost, the LSD group achieved a higher economic return on investment (ROI) of 16.92%. Our research results demonstrate that the aquaculture yield of gibel carp in the LBTAS is more than three times that of traditional ponds, with a return on investment reaching up to 16.92%. However, the HSD can negatively impact the growth performance, health status, and economic benefit of gibel carp. These results preliminary confirm the feasibility of the LBTAS, highlighting the importance of balanced aquaculture practices for sustainability and profitability. • A novel land-based tank aquaculture system coupled with effluent treatment ponds (LBTAS) was constructed. • The effluent contaminants in the LBTAS could be removed efficiently by coupled treatment ponds. • An appropriate stocking density in LBTAS was beneficial for the growth of gibel carp. • The aquaculture yield (kg/hm 2 ) of LBTAS was more than three times that of traditional pond farming.