The trematodes of fish of the transboundary Aras Dam Reservoir

In 2015–2018, in three localities representing the main ecological conditions of the Aras Dam Reservoir, 233 fishes of 19 species were studied by the method of complete helminthological dissection: Caspian roach – Rutilus caspicus, Caspian asp – Leuciscus aspius, Kura gudgeon – Romanogobio persus, Aras khramulya – Capoeta sevangi, Chаnari barbel – Luciobarbus capito, Kura barbel – Barbus laserta, South Caucasian bleak – Alburnus hohenackeri, Kura bleak – A. filippi, South Caspian spirlin – Alburnoides eichwaldi, bream – Abramis brama, golden carp – Carassius gibelio, common carp – Cyprinus carpio, Angora loach – Oxynoemacheilus angorae, South Caucasian spined loach – Cobitis satunini, catfish – Silurus glanis, mosquito fish – Gambusia affinis, zander – Sander lucioperca, round goby – Neogobius melanstomus, and bighead goby – Ponticola gorlap. As a result, 20 trematode species of two orders, nine families and 12 genera were found: Sanguinicola inermis, Bunodera luciopercae, Phyllodistomum elongatum, Orientocreadium siluri, Allocreadium isoporum, A. markewitschi, A. transversale, Acanthocreadium araxicum, Sphaerostomum bramae, Diplostomum chromatophorum, D. commutatum, D. helveticum, D. mergi, D. nordmanni, D. paracaudum, D. spathaceum, Tylodelphys clavata, Posthodiplostomum cuticola, Ichthyocotylurus pileatus, and Clinostomum complanatum. Of these, seven species were found in the fish intestine, and seven species in the lenses of eyes. Other organs had one trematode species each. One species is a specific parasite of catfish, one is a parasite of various predatory fish, seven species are parasites of cyprinid fish, and 11 species are parasites of fish of different families. According to the flow rate and the development of aquatic vegetation, the Aras Dam Reservoir can be divided into three parts. Eleven trematode species were found in the upper part, 17 species in the middle part, and 14 species in the lower part. The species richness is facilitated by the slow current and aquatic vegetation development, which attracts intermediate and definitive hosts - mollusks, crustaceans, fish, and birds. Among the trematodes found, nine species are fish pathogens, and one species is dangerous to human health if released into the digestive tract.