PARASITE FAUNA OF OHRID BLEAK (ALBURNUS SCORANZA, BONAPARTE, 1845) FROM OHRID LAKE (MACEDONIA)

Dijana BLAZHEKOVIKJ - DIMOVSKA, Stojmir STOJANOVSKI

Abstract

Ohrid Lake is the largest and most important natural lake in Macedonia, the oldest in Europe, and from a biological point of view, the most important stagnant water ecosystem on the continent. Ohrid bleak (Alburnus scoranza, Bonaparte, 1845) is numerous in the basin of the Neretva River, especially in the Ohrid and Skadar Lakes, in which it has a prominent economic importance. The scales of this fish are used to make the famous Ohrid pearl. The purpose of this study was to determine the presence of the parasite fauna in Ohrid bleak (Alburnus scoranza, Bonaparte, 1845) collected from Ohrid Lake. Fish material from seven (7) specimens of Ohrid bleak sampled from the Ohrid Lake, were subjected to routine identification, dissection, and observation, as well as, examined for parasitological investigations. Cleaned parasites were separated, put in appropriate fixatives, and prepared for determination using techniques of staining and clearing. The parasite specimens were identified using the reference keys of parasite determination. Common statistical analyses by calculation of prevalence and mean intensity of parasite species were used. The parasitological examination showed that 4 out of 7 examined fish specimens (57.14%) are infected with parasites. Four parasite species were identified, as follow: one monogenean (Dactylogyrus sp.) on the gills, one protozoan (Ichthyophthirius multifiliis) on the gills, one nematode (Raphidascaris acus) in the intestine and one cestode (Caryophyllaeus sp.) in the intestine. The most prevalent parasite species was Ichthyophthirius multifiliis (73.30%), while the highest intensity of infestation was recorded with Dactylogyrus sp. (5.43). The presence of parasites is detrimental to fish populations and can result in high mortality, weight loss, and reduced fertility in both aquaculture and open-water fish, especially in waters contaminated by industrial and urban pollutants. Poor water quality and lack of nutrients can cause the emergence of parasitic diseases. Parasites in the waters where they are present cause a decrease in the number of both juvenile and adult categories of fish, thus directly affecting the fish stock in a country.

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