During the parasitological examinations of the common carp (Cyprinuscarpio, L. 1758) from the Gradche Reservoir (Macedonia), a total of126 fish samples were examined, from which parasite infestation wasdetermined in 87 fish (69.05%). In this research, the following parasiticcopepods were identified: Ergasilus sieboldi, Ergasilus briani, and Lernaeacyprinacea. Ergasilus sieboldi was found on gills of common carp, with aprevalence of 1.461%, while the mean intensity was 2.357. Ergasilus brianiwas found on fins of common carp, with a prevalence of 1.879%, whilethe mean intensity was 38.274. Lernaea cyprinacea was found on the finsof common carp, with a prevalence of 0.552%, while mean intensity was2,000. Our findings of Ergasilus sieboldi, Ergasilus briani, and Lernaeacyprinacea in common carp are considered as first records for Macedonia.At the same time, common carp is a new host for Ergasilus briani inMacedonian waters.

A total of 958 specimens of farmed common carp Cyprinus carpio from eight of the most significant and largest cyprinid aquaculture facilities in Macedonia (pond and cage culture systems) were examined for parasitological investigation for three years. The following parasite species of the genus Dactylogyrus were identified: Dactylogyrus extensus, Dactylogyrus minutus and Dactylogyrus anchoratus . The highest prevalence was determined for D. extensus (38.8%), followed by D. minutus (7.9%) and D. anchoratus (2.8%). The highest mean intensity was determined for D. extensus (6.2), followed by D. minutus (4.7) and D. anchoratus (3.8). By seasons, the highest prevalence (16.5%) was recorded for D. extensus in winter, while the lowest (0.6%) for D. minutus in autumn. The highest mean intensity (8.0) was also determined for D. extensus in winter, and the lowest (1.9) for D. minutus in spring.

In our study, a total of 33 specimens of three cyprinid fish (Squalius squalus, Phoxinus lumaireul, and Pelasgus minutus) from Belčišta wetland (south-west Macedonia) were subjected to a parasitological investigation, by season. One specimen of Acanthocephalus lucii was found in autumn, in intestines of minnow (Phoxinus lumaireul Linnaeus, 1758). The record of Acanthocephalus lucii in minnow is considered as the first in N. Macedonia. At the same time, minnow represent a new host for this parasite worldwide.

Eight out of the eleven indigenous fish species of Prespa are endemic, i.e. they exist only in the Lake Prespa. One of these endemic fish species is Prespa bleak (Alburnus belvica). The parasitological examination from the Macedonian part of the Lake Prespa in 2023 showed that all of 14 examined specimens of Prespa bleak fishes were infested (100.0%). In our case study the presence of 8 parasite species was established: Gyrodactylus sp., Dactylogyrus alatus f. typica, Dactylogyrus fraternus, Dactylogyrus sphyrna, Posthodiplostomum cuticola (larva), Cestoda gen. sp. (larva), Raphidascaris acus (larva) and Ergasilus sieboldi. Individually, by the parasite species, the highest prevalence was with Dactylogyrus fraternus, Dactylogyrus sphyrna and Posthodiplostomum cuticola (larva) (71.43%). The lowest one was with Cestoda gen. sp. (larva) (7.14%). In our case study the parasites Gyrodactylus sp., Dactylogyrus fraternus and Cestoda gen. sp. (larva), are recorded for the first time in the ichthyoparasitofauna of Lake Prespa and Macedonia.

During a parasitological survey of Squalius squalus from Belčišta Wetland (Republic of North Macedonia), six parasite species found. These were Dactylogyrus sphyrna, Paradiplozoon ergensi, Gyrodactylus sp., Allocreadium isoporum, Proteocephalus torulosus and Pomphorhynchus bosniacus. The total helminth prevalence was 90.91%. The species with the highest prevalence were P. bosniacus (59.09%) and D. sphyrna (54.55%). The average intensity of infection was 6.08, with the highest values of D. sphyrna (7.83) and P. bosniacus (5.92). The present study is the first record of Proteocephalus torulosus in S. squalus in the Republic of North Macedonia. Among the parasite species found, the greatest pathological impact was associated with D. sphyrna, P. ergensi and P. bosniacus.

A total of 958 specimens of common carp from the most significant and larger cyprinid aquaculture facilities in Macedonia, including fish farms and reservoirs, were examined for parasitological investigations. Eudiplozoon nipponicum was found on gills in 121 specimens of common carp in spring, summer and autumn, with a prevalence of 10.67 %, and a mean intensity of 2.55. Our findings of E. nipponicum in common carp from aquaculture are first recorded in Macedonia.