Study of Fish Helminths Species Composition in the Middle Stream of Hrazdan River, Armenia
The ichthyogelminthofauna of the Hrazdan River has been little studied. The aim of the work was to identify the species composition of helminths of fish in the middle course of the river Hrazdan. The study of the helminthofauna of river fishes is of scientific and practical interest, especially in view of the increasing anthropogenic pressure in this region. In 2018, 86 specimens of fish of 6 species from Cyprinidae family were examined from the middle course of the river using the generally accepted method of parasitological autopsies. The overall invasiveness of the fish with helminths was 36%. In fish, monogenes, trematodes, cestodes, and nematodes were identified. 8 species of helminths were recorded. They were localized in the lens of the eyes, on the gills, in the body cavity and in the intestines of fish. In the fauna of fish helminths, biohelmints of 7 species dominate. Of these, metacercaria diplop and plerocercoids ligul are more common. 5 types of worms are generalists. 5 species are allogeneic, 3 species - autogenous. The impoverishment of the species composition of fish helminths is obviously a consequence of the impact of negative anthropogenic factors. The ichthyofauna of the Hrazdan River is different at different sites. In the lower reaches of the river, it is represented by more than 30 species, including the silver carp, the eastern swift fish, the Kura barbel, the Sevan temple, the Angora goletsir. Upstream, the species composition of fish is declining: only a few species are recorded - the silver carp, the Sevan temple, the eastern swift fish, the Kura barbel, etc. (Pipoyan, 2012). The helminthofauna of the Hrazdan river fish is little studied. The literature contains isolated data from the 1980s: in a survey of 22 specimens of crucian carp metacercariae by diplopost with up to 100% invasion were detected, plerocercoids liguli botriocephalus (Vartanyan, 1993). In 2016, the helminth fauna of fish in the upper reaches of the Hrazdan River was studied: 8 species of helminthes were found, the fish invasion was 37% (Oganesyan, Rukhkyan, 2018).