Level of infestation of bream monogenea in Volga reservoirs

Abstract

There are 9 reservoirs along the Volga River: Verkhnevolzhskoye, Ivankovskoye, Uglichskoye, Rybinskoye, Gorkovskoye, Cheboksarskoye, Kuibyshev, Saratovskoye and Volgogradskoye. They differ in geographical coordinates, average depth, average annual water temperature, hydrological and hydrochemical characteristics, oxygen content in water, diversity of flora and fauna, etc. Of the majority of fish species living in reservoirs, bream Abramis brama has the most important commercial value. Its abundance often undergoes considerable fluctuations under the influence of biotic and abiotic factors including parasitic infestation. The paper presents data on the numerical composition of gill ectoparasites of monogenes of the family Dactylogyridae. Dactylogyridae and Diplozoidae (Plathelminthes, Monogeneea) of bream living in Volga reservoirs. 101 specimens of bream were caught for the study in September 2019 and August 2020. Parasitological analysis of fish was carried out according to generally accepted methodology. The level of bream infestation was estimated according to the and parasite abundance index. A different number of monogenes of the family Monogenes were found in bream from the studied reservoirs. The number of monogenes of the family Dactylogyridae and Diplozoidae. In the Ivankovskoe reservoir 1498 specimens (1459 Dactylogyridae and 39 Diplozoidae), 1438 specimens (1420 and 18, respectively) were collected in the Uglich reservoir, Gorki Reservoir 78 specimens (68 and 10), Cheboksary 119 ex. (67 и 52), Kuybyshevskii 18 specimens (0 and 18, respectively) and Saratov 45 specimens (0 and 45). The highest indices of infestation by dactylogyruses were recorded in Ivankovskii and Uglichskii, and in Saratov diplozoans in Saratovsky. Differences in the level of bream infestation in the studied water bodies, probably due to the influence of different ecological factors.