Monitoring of invasions of family Percidae in the Volga-Caspian fishery basin

This paper presents long-term data on the occurrence of parasites of commercially valuable fish species, the common zander (Sander lucioperca (Linnaeus, 1758)) and the perch (Perca fluviatilis Linnaeus, 1758). The parasitofauna of perch fish was characterized by low species diversity, dominated by Nematoda. The component parasitic community was formed of host specific and euryxenic species with direct and complex development cycles. Species of epizootic and/or epidemiological significance common to perch and zander included Apophallus donicus Skrjabin & Lindtrop, 1919, Anisakis schupakovi Mosgovoi, 1951; Eustrongylides excisus Jägerskiöld, 1909; Corynosoma strumosum Rudolphi, 1802; Achteres percarum Nordmann, 1932; Argulus sp., and Piscicola geometra Linnaeus, 1761. The dynamics of infection of fish with most parasites showed seasonal variability. The larvae of the nematode E. excisus and the crustacean A. percarum caused a pathological response in the body of their host, whereas other species were asymptomatic parasites. The changes revealed in the occurrence and intensity of infection are due to the biological characteristics of the parasites and their hosts, as well as the means of transmission of the invasion. The annual presence and low levels of parasite infestation suggest stability of parasite-host relationships in perch fish. However, the presence of pathogens of invasive diseases indicates the maintenance of natural foci of parasitosis in the Volga-Caspian fishery subarea. Parasitic diseases being at the subclinical level suggest that the parasitological state of perch fish is satisfactory