Fish physiology and biochemistry ·7 Nov 2026 ·Added 10 Nov 2026

High stocking density impaired growth and induced oxidative stress, lipid metabolism disorder, and ferroptosis in grass carp (Ctenopharyngodon idella).

Sayed R S Zidan, Yutian Yuan, Wenhan Li, Huacheng Li, Tingting Xu, Rong Tang, Li Li, Liqin Yu, Dapeng Li

Other & Emerging Fields

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Abstract

Intensive aquaculture via increasing fish density became an inevitable choice to increase aquaculture output. However, crowding stress compromises growth and fish health. The present study investigated the impacts of stocking density on growth, stress responses, oxidative status, lipid metabolism, and ferroptosis in grass carp. Fish (128.02 ± 2.35 g) were reared at three densities: LSD (low stocking density, 5 kg/m3), MSD (medium stocking density, 10 kg/m3), and HSD (high stocking density, 20 kg/m3) for 65 days in the recirculating aquaculture system (RAS). The results showed that increasing fish density negatively influenced the growth performance and feed utilization. The HSD group induced a stress response by significantly increasing the serum cortisol, glucose, and cholesterol levels, as well as AST and ALT activity. Crowding stress conditions induced oxidative stress and ferroptosis, marked by depleted antioxidants including catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), and total antioxidant capacity (T-AOC), decreased glutathione peroxidase 4 (GPX4), while raising malondialdehyde (MDA) and iron content in both serum and hepatopancreas tissue (p < 0.05). Additionally, transcriptomic analysis detected that HSD treatment changed lipid metabolism and promoted ferroptosis. Interestingly, HSD treatment prompted fatty acid synthesis, causing an increase in polyunsaturated fatty acids (PUFAs) synthesis and their elongation (acaca, acsbg1, elovl2, elovl5, and elovl6 were upregulated), while it suppressed fatty acid oxidation (cpt1ab and dgat2 were downregulated), diverting PUFAs toward membrane phospholipids. Furthermore, PUFAs overflow into acsl4 (upregulated) increased membrane lipid peroxidation, and gpx4 (downregulated) failed to reduce resulting lipid hydroperoxides, causing ferroptosis execution. In conclusion, chronic crowding stress disrupts growth, causes physiological responses, and disrupts hepatopancreas health by inducing oxidative stress, altered lipid metabolism, and induced ferroptosis in grass carp reared in RAS.