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Abstract:

This paper studied the effect of nickel derived from nickel acetate (Ni (NO₃)₂), in three concentrations of nickel (3, 6 and 9 mg·l^-1of water) on some physiological indexes in two species of native fish (Carassius auratus gibelio Bloch and Rhodeus sericeus amarus L.). The consumption of oxygen in both investigated species decreased significantly after the first 24 hours of exposure to nickel (with more than 30% as compared to control values) for all the three investigated concentrations, the values determined subsequently showing gradual increase from one determination to the other, with the re-establishment ofthe energetic metabolism being slower in the Prussian carp (Carassius auratus gibelio) as compared to the European bitterling (Rhodeus sericeus amarus). The respiratory rate of the fish exposed for 7 days to the 3 investigated sub-lethal concentrations of Ni also increased progressively (except for the values measured after 24 hours of exposure),until the 7^th day of exposure,the values of this index determined after 336 hours being significantly lower than the control values. To be noted that the for the European bitterling, the frequency of the opercular movements after 14 days of exposure to the threeNi concentrations does not show significant changes as compared to the values registered after 24 hours from the immersion of fish into the Ni solutions. Averageglycaemia and blood cell count values in the case of groups treated with Ni increased significantly, the most pronounced increases being recorded at the highest concentration of nickel (9 mg·l^-1 of water; at this concentration the glycaemia levels exceeded almost four times the values recorded in the control group at both species).In conclusion, the changes observed indicate that investigated physiological parameters can be used as an indicator of Ni related stress in fish on exposure to elevated Ni levels.