UTTAR PRADESH JOURNAL OF ZOOLOGY

Aquatic ecosystems are increasingly contaminated by pesticides and heavy metals because of industrialisation, urbanisation, mining activities and intensive agricultural practices. These contaminants accumulate in water bodies and adversely affect fish physiology, metabolism, growth, reproduction and survival. Heavy metals such as cadmium, mercury, lead, chromium and arsenic are persistent, non-biodegradable pollutants that bioaccumulate in fish tissues and biomagnify through aquatic food chains. Similarly, pesticide groups, including organophosphates, organochlorines, carbamates and pyrethroids, interfere with enzymatic activity, endocrine function and cellular metabolism in fish. Exposure to these toxicants induces oxidative stress, disrupts carbohydrate, protein and lipid metabolism, alters haematological and biochemical parameters, and damages vital organs such as the liver, gills, kidney and brain. Fish exposed to toxic pollutants may also exhibit behavioural abnormalities, immune suppression, histopathological alterations and impaired reproductive performance. Evidence discussed in this review indicates that these toxic effects are mediated through the generation of reactive oxygen species, mitochondrial dysfunction and changes in gene expression associated with detoxification pathways. Several remediation strategies have been developed to reduce aquatic pollution and protect fish health, including microbial bioremediation, phytoremediation using aquatic plants, adsorption techniques, nanotechnology-based remediation, probiotics and medicinal herbs. Advanced molecular and biochemical approaches are also being explored for the sustainable management of contaminated aquatic systems. This review summarises the major toxic effects of pesticides and heavy metals on fish metabolic activities, discusses physiological and molecular mechanisms of toxicity, highlights relevant research findings and evaluates current remediation strategies for maintaining ecological balance, food safety and sustainable aquaculture production. The synthesis is intended to support cautious interpretation of pollutant effects and remediation needs.