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The circulation of the contents of Cu, Cd, and As was traced in the system of Chondrostoma nasus – Pomphorhynchus laevis – Contracaecum sp. – water – sediments from the Danube River in the Kudelin biotope. New data on the content of the elements examined are presented. The concentrations of the three elements in the materials studied, which included tissues, organs, and parasites of common nase, and water and sediments from the Kudelin biotope, were higher than the limits set forth in Bulgarian and international legislative documents. The bioindicator role of the tissues, organs, and parasites examined was revealed, and the liver of common nase and Contracaecum sp. were good bioindicators for Cd content, while P. laevis was a good bioindicator for As content.

In the autumn of 2022, 37 specimens of Orpheus dace (Squalius orpheus Kottelat & Economidis, 2006) were subjected to helminthological examination. The fish were caught from the lower section of the Chepelarska River (in the area of Katunitsa village). Three endohelminth species were isolated - Acanthocephalus tenuirostris (Achmerov & Dombrovskaja-Achmerova, 1941) Yamaguti, 1963 (class Trematoda), Contracaecum sp., Rhabdochona denudata (Dujardin, 1845) Railliet, 1916 (class Nematoda). The component community and infracommunity of Orpheus dace were reviewed. One core species (Contracaecum sp.; P% = 32.43) was found in the component community of Sq. orpheus. Brillouin's diversity index (HB), Pielou's evenness index (E), and Simpson's dominance index (C) were calculated. The research aims to provide data on the helminths and helminth communities of Orpheus dace from the freshwater ecosystem of the Chepelarska River. The studied biotope (Katunitsa) is a new habitat for the found helminth species of Orpheus dace. [ABSTRACT FROM AUTHOR]

During the period 2019-2021, the helminth fauna of two species of freshwater fish of the family Cyprinidae, genus Ballerus Heckel, 1843 - white-eye bream (Ballerus sapa (Pallas, 1814)) and zope (Ballerus ballerus (Linnaeus, 1758)) were examined. Six specimens of white-eye bream and one specimen of zope were collected from a total of three biotopes located in the Bulgarian section of the Danube River between 845 and 807 river km. Three species of helminths were found - 2 species of the class Trematoda (Asymphylodora imitans (Mühling, 1898) Looss, 1899; Nicolla skrjabini (Iwanitzky, 1928) Dollfus, 1960)) and 1 species of the class Nematoda (Contracaecum sp. (larvae)). The present study aims to provide new data on the species composition and helminth ecological indices of the two examined fish species. B. sapa is reported as a new host record for the three helminth species in Bulgaria. Koshava biotope is a new habitat for the established helminths in the white-eye bream. [ABSTRACT FROM AUTHOR]

For the period 2019-2021, an ecoparasitological study of six fish species - grass carp (Ctenopharyngodon idella Valenciennes, 1844); silver carp (Hypophthalmichthys molitrix Valenciennes, 1844); pumpkinseed (Lepomis gibbosus Linnaeus, 1758); Prussian carp (Carassius gibelio Bloch, 1782); gudgeon (Gobio gobio Linnaeus, 1758); European bitterling (Rhodeus amarus Bloch, 1782) was conducted. The fish were caught from 3 biotopes (Koshava, Kudelin, Novo selo) from the upper section of the Danube River in Bulgaria. A total of two parasite species (Pomphorhynchus laevis Zoega in Müller, 1776) Porta, 1908 and Contracaecum sp. (larvae) were found in two of the investigated fish species. Four fish species were not infected. The ecological indices (mean intensity; mean abundance; prevalence) of parasites were calculated. Kudelin and Koshava biotopes are new habitats for the found helminth species of the infected fish species. [ABSTRACT FROM AUTHOR]

For the period 2019-2021, three fish species of the family Cobitidae, caught from the upper section of the Danube River in Bulgaria, were subjected to ecologohelminthological investigation. Four specimens of Cobitis elongata Heckel & Kner, 1858 (two specimens from Kudelin biotope and two from Koshava biotope); six specimens of spined loach (Cobitis taenia Linnaeus, 1758) (from Koshava biotope) and one specimen of Sabanejewia bulgarica Drensky, 1928 (from Kudelin biotope) are objects of research. The trematode Asymphylodora tincae (Modeer, 1790) Lühe, 1909 was reported for the first time as a helminth of S. bulgarica. The nematode Pseudocapillaria tomentosa (Dujardin, 1845) Moravec, 1987 was reported for the first time as a helminth of C. elongat?. Kudelin and Koshava biotopes are new habitats for the found helminth species. During the helminthological examination of C. taenia, infection with helminths was not found. The study provides new data on helminth fauna and ecological indices (MI, MA, and P%) in the helminth communities of C. elongat? and S. bulgarica. [ABSTRACT FROM AUTHOR]

During 2019-2021, six specimens of pontic shad (Alosa immaculata Bennett, 1835); family Clupeidae were examined for parasites. The specimens were collected from three biotopes (Kudelin, Yasen, and Koshava) located in the section of the Danube River in the northwestern part of Bulgaria. Infection with 3 species of helminths was found - 1 species of the class Trematoda (Lecithaster confusus Odhner, 1905); 1 species of the class Acanthocephala (Pomphorhynchus laevis (Zoega in Müller, 1776) Porta, 1908) and 1 species of the class Nematoda (Hysterothylacium gadi aduncum (Rudolphi, 1802) Deardorff et Overstreet, 1981 (larvae)). Ecological indices of the found helminth species were examined. The purpose of the study is to provide new data on the helminth fauna of the pontic shad from the freshwater ecosystem of the Danube River in Bulgaria. Al. immaculata is a new host for one endohelminth species (L. confusus). Two of the investigated biotopes (Koshava and Yasen) are new habitats for the found endohelminths in pontic shad. [ABSTRACT FROM AUTHOR]

In the spring of 2020, ecoparasitological studies were conducted on 30 specimens of common nase (Chondrostoma nasus (Linnaeus, 1758)) from the freshwater ecosystem Danube River near Kudelin village, northwestern Bulgaria. Two parasite species were determined. One species - Proteocephalus torulosus (Batsch, 1786), juvenile, belongs to the class Cestoda. The other one - Contracaecum sp., larvae, belongs to the class Nematoda. C. nasus is a new host for P. torulosus in the studied area. In the study, Contracaecum sp., larvae was a core parasite species (P% = 90.00) in the component community of C. nasus from the Danube River (Kudelin). For Contracaecum sp. larvae, the highest mean intensity (MI = 18.15) and the highest mean abundance (MA = 16.33) were found. [ABSTRACT FROM AUTHOR]

In 2020, 37 specimens of vimba bream (Vimba vimba Linnaeus, 1758) from the Danube River near the village of Kudelin were examined for parasites. Four parasite species were established: Nicolla skrjabini (Iwanitzky, 1928) and Posthodiplostomum cuticola (von Nordmann, 1832) (Trematoda); Pomphorhynchus laevis (Zoega in Müller, 1776) (Acanthocephala) and Philometra rischta Skrjabin, 1917 (Nematoda). The study aims to provide new data on parasites and parasite communities of Vimba vimba from the Danube River’s freshwater ecosystem near the village of Kudelin in northwestern Bulgaria. In the study, the prevalence (P%), mean intensity (MI), mean abundance (MA) and the Brillouin’s diversity index (HB) were presented and discussed. [ABSTRACT FROM AUTHOR]

In 2019, studies on the parasites and parasite communities of Chondrostoma nasus (Linnaeus, 1758) from the Danube River, Bulgaria (Koshava and Kudelin villages, Vidin region) were conducted. After ecoparasitological studies of a total of 155 specimens of C. nasus from the two biotopes, eight species of parasites were found: two species of the class Trematoda (Allocreadium isoporum (Looss, 1894), Sphaerostomum bramae (Müller, 1776)), one species of the class Cestoda (Bothriocephalus acheilognathi (Yamaguti, 1934, immature specimens)), one species from the class Acanthocephala (Pomphorhynchus laevis (Müller, 1776)) and four species from the class Nematoda (Raphidascaris acus (Bloch, 1779), larvae; Contracaecum sp., larvae; Hysterothylacium sp., larvae; Pseudocapillaria tomentosa (Dujardin, 1843)). The majority of parasite species (seven species) were detected during the spring from biotope Kudelin. The dominant parasite species in all three seasons was the nematode Contracaecum sp. C. nasus was reported as a new host for A. isoporum, S. bramae, B. acheilognathi, R. acus, Contracaecum sp., Hysterothylacium sp., P. tomentosa from the Bulgarian section of the Danube River. New data on the structure of parasite communities of the river freshwater ecosystem were presented. [ABSTRACT FROM AUTHOR]

In the spring, summer and autumn of 2019, ecoparasitological studies were conducted on 165 specimens of Alburnus alburnus (Linnaeus, 1758) from the Danube River (Koshava, Kudelin and Novo selo villages, Vidin region). The species diversity of parasites of the bleak was determined. Seven species of parasites were identified: 4 species of Trematoda (Nicolla skrjabini (Iwanitzky, 1928), Allocreadium isoporum (Looss, 1894), Posthodiplostomum cuticola (von Nordmann, 1832), Sphaerostomum bramae (Müller, 1776)), one species of Cestoda (Neogryporhynchus cheilancristrotus (Wedl, 1855), larvae), one species of Acanthocephala (Pomphorhynchus laevis (Müller, 1776)) and one species of Nematoda (Contracaecum sp., larvae). In the spring the dominant species was the trematode A. isoporum, detected in 9 specimens of A. alburnus from the Koshava biotope. The dominant parasite species in summer and autumn was the trematode P. cuticola. A. alburnus is a new host for S. bramae and N. cheilancristrotus, from the studied river ecosystem. The structure of the parasite communities of the bleak from the investigated section of the freshwater ecosystem of the Danube River was presented. [ABSTRACT FROM AUTHOR]

The multifunctionality of agriculture is a crucial element of the system of the national economy. Land preservation and restoration is the main objective in the strategy of multifunctional agriculture, ensuring the provision of necessary food products and raw materials for the next generation. Multifunctional agriculture occurs mainly in the countries members of the EU, though its development is at a different level depending on the situation in individual countries. The aim of the study is to analyze the social and economic effects of the application of multifunctional agriculture. The study is based on good practices of different farms in Bulgaria and Germany. The results show that multifunctional agriculture provides a stable social and economic development of agricultural farms and contributes to the development of vital rural regions in which they are located. [ABSTRACT FROM AUTHOR]