SUBLETHAL EFFECTS OF NICKEL TO RAINBOW TROUT ONCORHYNCHUS MYKISS BIOLOGICAL PARAMETERS

Abstract

The aim of this study was to assess sublethal effects of nickel on rainbow trout juveniles evaluating alterations in fish biological parameters - behavioral responses, hematological, morphological parameters and physiological indices. The study of the responses of rainbow trout to different concentrations of nickel demonstrated their different effect on fish organism. Feeding behavior of test-fish showed their adaptation to lower nickel concentrations (0.1 mg/L, 0.2 mg/L). Higher concentration of nickel (0.4 mg/L) had affected fish feeding irreversibly. There was no significant effect on fish ventilation frequency during exposure to 0.1 mg Ni/L concentration. Ventilation frequency decreased during exposure to 0.2 mg Ni/L, and 0.4 mg Ni/L, which leaded to increase in coughing rate. Hematological indices of fish were affected during exposure to 0.2 mg Ni/L, and 0.4 mg Ni/L concentrations. Erythrocyte, leucocyte count, haematocrit level and haemoglobin concentration had decreased significantly at 0.2 mg Ni/L, and 0.4 mg Ni/L concentrations. No significant changes in glucose concentration were found during the exposure to all nickel concentrations tested. Present investigation confirmed different sensitivity of the morphophysiological parameters studied, the most sensitive ones were: gill somatic > liver somatic = spleen somatic indices. This study showed that nickel even at low concentrations can affect biological parameters of fish. This phenomenon can lead to revision of Maximum-Permissible-Concentration of nickel in ambient water.