Levels of tetracycline and sulphonamide residues in freshwater fish: A systematic review and meta-analysis

The widespread use of antibiotics in freshwater aquaculture has raised significant global concerns because of the accumulation of antibiotic residues in fish and the associated risks to human and environmental health. Tetracyclines and sulphonamides, two of the most applied antimicrobial classes, are of particular interest owing to their broad-spectrum activity, environmental persistence, and ability to select for resistant bacterial populations. This systematic review and meta-analysis conducted using the Population-Exposure-Outcome (PEO) framework, synthesised global evidence on the occurrence of these residues in commonly farmed freshwater fish. Thirty-three studies published between 2005 and 2022 were included. Pooled mean concentrations for tetracyclines were: tetracycline, 18.13 μg/kg (95% CI: 8.16–28.09; Q(12) = 5148.18, I² = 99.98%, p < 0.001); oxytetracycline, 104.76 μg/kg (95% CI: −16.09–225.61; Q(14) = 72,693.12, I² = 100%, p < 0.001); and doxycycline, 47.79 μg/kg (95% CI: −5.92–101.49; Q(6) = 13.15, I² = 100%, p = 0.02). For sulphonamides, pooled means were: sulphonamerazine, 0.27 μg/kg (95% CI: 0.19–0.35; Q(5) = 76.41, I² = 81.62%, p < 0.001); sulphadiazine, 29.84 μg/kg (95% CI: −2.36–62.03; Q(8) = 29,816.14, I² = 100%, p < 0.001); and sulphathiazole, 3.57 μg/kg (95% CI: 0.27–6.87; Q(6) = 6427.72, I² = 99.91%, p < 0.001). Subgroup analyses revealed consistently higher residue levels in Asian aquaculture systems, notable variation across analytical detection methods, and species-specific differences in bioaccumulation. Collectively, these findings demonstrate persistent antimicrobial contamination in freshwater fish and highlight potential dietary exposure risks. They underscore the urgent need for harmonised monitoring protocols, strengthened regulatory enforcement, and improved antimicrobial stewardship to safeguard public health and support sustainable aquaculture practices.