In recent years, the impact of aquatic pollution on human and animal life has become a matter of great concern. Fish responses have been used as biomarkers of aquatic pollution. The use of a suitable biomarker with different degrees of specificity is an important aspect of environmental monitoring based on biomarkers. In this direction an effort has been made to develop the biomarker responses as an early warning signal in pollution assessment. Studies were conducted on the different sites of river Yamuna for assessing the pollution profile. The oxidative responses, as well as antioxidant potential of fish differed in relation to species, habitat and feeding behaviour. The levels of heavy metals and pesticides were also found to be in varied concentrations at different sites. When comparisons were made between two sites, (Yamunanagar and Mathura), results revealed that Mathura site was more polluted compared to Yamunanagar. The water samples of Yamunanagar did not show any traceable amount of heavy metal and pesticides when compared to that of Mathura sample. The results obtained provide an insight for the assessment of non-enzymatic antioxidants at two different sites for their successful use as biomarkers.

          An attempt was also made to study protein carbonyl as a biomarker of exposure in fish. Use of protein carbonyl has been well documented in humans and rodents. Till date no study has been reported in case of fish. The present study has shown a biomarker approach using the protein carbonyl content in fish. A significant increase in protein carbonyls have been observed in all groups of fish exposed to different pesticides. Assay of carbonyl groups in proteins provides a conventional technique for detecting and quantifying oxidative modification of proteins. A study was undertaken to investigate the modulatory role of copper on non-enzymatic antioxidants viz., protein and non-protein thiols, ascorbic acid and metallothionein. It was also intended to investigate possible regulatory role of copper on iron in fish. The findings of the present investigation provided a new insight into the multifarious role of low-level exposure to copper in fish. It seems to protect the fish from peroxidative damage by inducing both non-enzymatic antioxidants and possibly antioxidant enzymes by the induction of ceruloplasmin and metallothionein. Findings of this study will be helpful in pollution monitoring and identification of pollutant-sensitive and pollutant-resistant Indian fish species. It will enable us to predict the pollution profile of an aquatic habitat viable for fishery activities. It will also contribute to the development of a battery of mechanism-based biochemical assays that can be used to characterize the complex mixtures of chemicals in different potentially toxic environments and thus enhance our ability to assess the long-term risk of environmental contaminants to human health.