UTTAR PRADESH JOURNAL OF ZOOLOGY

Textile dyeing and finishing operations discharge coloured, chemically complex wastewater into freshwater systems that support fisheries, aquaculture and drinking-water abstraction. Fish exposed to such discharges display a recurring suite of alterations spanning redox biochemistry, genetic integrity, tissue architecture, haematology, behaviour and gut microbial composition. Whether these alterations constitute a coherent, mechanistically understood stress syndrome remains contested. This critical narrative review evaluates the strength, internal consistency and methodological quality of the evidence linking dye-bearing effluents and their constituent dyes to stress responses in freshwater fishes, and distinguishes conclusions that the literature supports from those that it does not. Verified peer-reviewed studies retrieved from openly accessible bibliographic indexes were appraised for exposure characterisation, concentration realism, biomarker interpretation and analytical transparency. Three findings emerge with reasonable confidence: exposure to dye-containing wastewater and to individual dyes elevates markers of lipid peroxidation and induces cytogenetic damage in erythrocytes across taxonomically diverse species; gill and liver are consistently the most severely affected organs; and conventional treatment reduces colour and organic load more effectively than it reduces biological hazard. Three areas remain unresolved. Antioxidant enzyme responses are directionally inconsistent across studies of the same dye and species, and this inconsistency is rarely analysed rather than described. Most laboratory exposures use concentrations one to five orders of magnitude above measured environmental levels, so the ecological meaning of reported effect thresholds is uncertain. Attribution of observed damage to parent dyes, to their reductive cleavage products or to co-occurring salts, metals and surfactants is almost never established experimentally. Neuroendocrine mediation, in particular the hypothalamic-pituitary-interrenal axis, is largely unexamined despite being the canonical vertebrate stress pathway. Priorities include quantified exposure characterisation, effect-directed attribution, chronic and multigenerational designs at environmentally measured concentrations, and standardised reporting of biomarker directionality.