Abstract: Ohrid trout as an endemic relict and economical important species is the most important fish in Lake Ohrid (Europe oldest). In the latest years the stock declined. This fact was linked to the heavy fishing pressure and also to environmental toxicants. The objective of our pilot study was to map the occurrence of liver lesions in Ohrid trout in various areas suspected to be under diverse degrees of pollution. So, 70 female livers were obtained from 2000 to 2002, at tree sites (North to South): Andon Dukov-Virce, Pestani and Veli Dab-Trpeica. Considering all sites, we found the following lesion types (and proportion of affected fishes): lymphocytic infiltration, necrosis, cholangiofibrosis, bile duct hyperplasia plus regressive changes in biliary epithelial cells, and parasites within intrahepatic bile ducts often accompanied with macrophages proliferation. Despite lesions were non-neoplastic in nature, and that bile duct hyperplasia may result from regeneration secondary to necroinflammatory lesions, biliary epithelial cell dysplasia was found in some cases. Despite the % of fish with lesions steeply declined from the urban sites of Andon Dukov-Virce (40%) to Pestani (27%), and further South to the cleaner areas of Veli Dab-Trpeica (7%), the % of specific lesions or amount (relative volume) of macrophages was not statistically associated with the sampling location. Although the study is limited regarding fish number, it supports that there are pollution gradients / effects along the southeastern coast of Ohrid Lake and that local contaminants may be stressing this unique threatened species in diverse ways.

Maja Jordanova¹, Eduardo Rocha², Nada Miteva¹

¹Faculty of Natural Sciences and Mathematics, ²Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto

Keywords: liver , pathology , Ohrid trout