Histopathological Effects of Chronic Exposure to Cadmium and Zinc on Kidneys and Gills of Brown Trout (Salmo trutta m. fario)

The aim of the present study was to investigate the histopathological changes on the organs of the brown trout (Salmo trutta m. fario) inflicted by per oral cadmium and zinc poisoning in the 46- week experimental period. The fish were kept in well-oxygenated freshwater basins which were purposely set for the experiment. During the investigation, we set up two experimental basins along with the control one. We put 30 specimens of one-year-old brown trout of the average weight of 15 grams in each basin. According to Venugopal, peroral toxic doses for fish can not be determined precisely. Accurate lethal doses (LD50 and LD) can only be established for a number of laboratory animals. However, it is possible to calculate the approximate toxic doses for fish from peroral lethal doses for rats. The calculated values for cadmium chloride are 4, 4 mg/kg and 11 mg/kg for zinc sulphate, respectively. In the experimental stage we soaked the fish food in solutions made in conformity with the aforementioned values of cadmium chloride and zink sulphate. As a result, the fish consumed the aforementioned toxic doses in the experimental stage, considering that the feeding regimen included the food ration of 2% body weight/day.