Liver Histopathology in Brown Trout (Salmo trutta f. fario) from the Tinhela River, Subjected to Mine Drainage from the Abandoned Jales Mine (Portugal)

The objective of this study was to compare the occurrence of toxicopathic liver lesions in brown trout (Salmo trutta fario) from Tinhela River near the Jales Mine, both before implementation (2002) and after completion of the governmental mitigation program (2006). Fish were caught in April 2002 and May 2006, using an electrofishing system at four sites: S0, reference station; S1, S2 and S3 as contaminated stations. In 2002, the hepatosomatic index (HSI) was significantly higher for trout captured at the contaminated sites S2 and S3 than in S0. After the rehabilitation program, the HSI of fish sampled at the contaminated sites did not differ from the reference group. The liver of trout caught at S0 exhibited the normal parenchymal and stromal architecture described for the species and there were no pathological abnormalities. In contrast, fish sampled at S3 and S2 sites had diverse toxicopathic alterations. Specifically, livers from the two contaminated sites showed bile duct hyperplasia, often with mild epithelial dysplasia and fibrotic adventitial sleeve, foci of smaller and more basophilic hepatocytes and foci of hepatocellular necrosis; the latter conditions were frequently associated. Compared with the reference animals, increased hepatocellular vacuolization was found in livers from the polluted sites. Histopathological examination revealed differences among sampling sites in the severity and diversity of hepatic lesions clearly related to the proximity of the tailings. No pathological alterations were observed in the livers of brown trout caught in the same four areas of the Tinhela River after the mitigation program in 2006. In conclusion, our results supported that drainage from the abandoned Jales Mine had deleterious toxicological effects in brown trout. Our data suggested that the governmental mitigation program may have reduced the impact of Jales tailings.