The objective of this study was to characterize the genetic structure of two Balkan brown trout morphotypes, Salmo macedonicus and Salmo pelagonicus, and to test whether molecular traits support the species' status proposed by traditional morphological identification. The mitochondrial DNA 12S-rDNA, cyt b and control region genes were sequenced in 15 specimens collected from three localities in the Former Yugoslav Republic of Macedonia. The results of these markers did not support the taxonomic category of species but confirmed the existence of two morphotypes, Salmo trutta macedonicus and Salmo trutta pelagonicus, in the Aegean-Adriatic lineages of the Salmo trutta species complex.

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During parasitological investigations six species of monogenean trematodes were found on the gills of three cyprinid fish species from Lake Prespa (Macedonia), as follows: Dactylogyrus prostae and Dactylogyrus sphyrna in Leuciscus cephalus albus, Dactylogyrus erhardovae, Dactylogyrus sphyrna and Paradiplozoon zeller in Rutilus rubilio prespensis and Dactylogyrus elegantis and Dactylogyrus vistulae in Chondrostoma nasus prespensis. The prevalence in Leuciscus cephalus albus was 62.22%, in Rutilus rubilio prespensis 59.87% while in Chondrostoma nasus prespensis it was the lowest and amounted to 41.59%. The overall, prevalence of monogeneans in the investigated cyprinid fishes from Lake Prespa was 53.65%, and the mean intensity of infestation was 6.08. Among the monogenean species the highest prevalence occurred with Dactylogyrus sphyrna (25.08%), and the greatest intensity of infestation was evident in the cases of infestation with Dactylogyrus erhardovae (12.87). The greatest pathological effect was associated with the monogeneans Dactylogyrus vistulae and Paradiplozoon zeller. All monogenean species found represented the first record for such parasite fauna of fishes in Macedonia

Discocotyle ohridana n.sp. is described from the gills of Ohrid belvica Salmothymus ohridanus Steindachner, 1892; (syn. Acantholingua ohridana Hadzisce, 1961) from the Lake Ohrid, Macedonia. According our investigation the new species D. ohridana n.sp. differs 56.47% of observed S. ohridanus have been infected and average intensity of infestation is 2.84.

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