Untitled

Abstract

Ohrid trout stock levels have been declining for decades in the Europe's oldest lake, Lake Ohrid, between Albania and Macedonia. Limited datasets indicate that this decrease is linked to overfishing and pollution. Histopathological hepatic lesions in fish have been regularly strongly associated with exposure to chemical contaminants. We collected baseline information on the toxicopathological and other lesions on this species liver, from 3 sites adjacent to 2 highly urban and 1 much less urban areas along the lake's eastern coast during 2000-2002. In addition, changes in the relative volume of pigmented macrophages were used as proxies of immune-mediated responses. The percentage of fish with pathological changes declined steeply from the 2 urban sites (40% and 27%) to the pristine site (7%). In addition, fish with lesions tended to have greater amounts of pigmented macrophages, with fish from the pristine site having significantly fewer lesions. While the number of fish analyzed was limited (n = 70), the biomarkers suggest the presence of a pollution gradient (decreasing towards south) along the eastern coast of Lake Ohrid. Despite scarce, other kind of data agree with our hypothesis. Variations of pigmented macrophages and liver toxicopathic injuries warn of the health impacts of urbanization on this endangered trout. This study supports the need to initiate a long-term biomonitoring program for this species as an index of the health status of Lake Ohrid.