Studies were conducted to evaluate the antimicrobial potency of skin mucus collected from three carp species; Hypophthalmichthys nobilis, Ctenopharyngodon idella, and Cyprinus carpio (exotic to India) against certain human and fish pathogenic bacterial strains viz. Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, and Aeromonas hydrophila. The antimicrobial activities were measured in terms of zone of inhibition (ZOI) in mm and compared with two antibiotics (amikacin and chloramphenicol). All selected fish species were also challenged with A. hydrophila through water to check, if there is any change in mucus secretion or its antibacterial effects. Studies have shown that after challenge with A. hydrophila, an increase in mucus secretion was observed in all the three species of carps. Skin mucus extracts (crude and aqueous) obtained from healthy and challenged fish species exhibited strong antibacterial activity against all the investigated microbial strains. Variations in antibacterial effect have been observed among same fish (in healthy and challenged) and amidst different carp species against same and different bacterial strains. In general, crude mucus of all the fish species showed higher bactericidal action than its aqueous extracts and antibiotic chloramphenicol. Hence, these results have clearly revealed that the mucus obtained from fish skin shows antibacterial activity which may play an important role in fish protection against pathogens and thus there appears to be a possibility of using mucus obtained from the skin of carps as an alternative to antibiotics in animals and possibly also in human health related problems.

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The purpose of the present study was to evaluate the severity of pollution impact at two extreme sites of river Yamuna in Delhi region utilizing oxidative stress, genotoxic and histopathological biomarkers in gonad (ovary) of Clarias gariepinus. To evaluate oxidative stress, TBAR's and ferric reducing antioxidant power (FRAP) assay were employed while comet assay and classic histology were used to estimate genotoxicity and cellular damage respectively. The results indicated significant increase (p < 0.001) in TBARs level (µmol/g wet tissue); significant decrease (p < 0.001) in FRAP value (U/mg tissue), significant increase (p < 0.001) in DNA damage and extensive abnormal histoarchitecture in ovarian samples procured from Okhla as compared to Wazirabad barrage. Thus, exposure to the increasing toxicity downstream the river is altering the activity of cellular total antioxidant capacity persuading oxidative stress and cellular damage, eventually distressing the heath of fish fauna directly and humans indirectly.

River Yamuna is under constant menace due to pollution levels beyond limit, ensuing chronic poisoning of aquatic biota. Induction of oxidative stress and cellular deformities is a common effect in fish. The present study aimed in assessing impact of environmental pollutants on gonad (testis) of Clarias gariepinus from Wazirabad barrage (entry site) and Okhla barrage (exit site) of river Yamuna in Delhi segment. Antioxidant enzymes assays viz. Super oxide dismutase (SOD), catalase (CAT) and ferric reducing antioxidant power (FRAP); thiobarbituric acid reactive substance assay (TBARS) for determining level of lipid peroxidation and histology for analysis of degenerative changes were employed as biomarkers. The results depicted signs of environmental contamination, hallmarked by significant increase (p < 0.001) in TBARs level (µmol/g wet tissue); significant decrease (p < 0.001) in SOD, CAT (U/mg protein) and FRAP value (U/mg tissue) in response to greater pollution at Okhla barrage as compared to Wazirabad barrage. Degenerative changes viz. unorganized seminiferous tubules, extensive vacuolization in germ cells, inflammatory lesions, greater vacant spaces and condensation of tubular cells prevailed in 75%, 85%, 80%, 80%, and 65% specimens respectively from Okhla barrage. Hence, the selected biomarkers highlighted the existence of greater prooxidative compounds at the exit site resulting in stressful condition for fish in river basin.