Spring dynamics of cyprinids parasitofauna under pond aquaculture conditions in the Astrakhan region

The results of spring monitoring of invasive diseases of Cyprinids in fish farms of the Astrakhan region are presented. Indicator representatives of the main species groups of the ectoparasite fauna of Cyprinids (monogenetic trematodes, fish leeches, crustaceans and unicellular skin parasites) are considered, and the quantitative dynamics of invasions in spring season under aquaculture conditions in the Astrakhan region are considered. In the period from April to May 2020, 170 samples of carp fish of five species were examined: carp, bream, roach, silver bream, rudd. The study was carried out by the parasitological method on live fish, the intensity of invasion was determined. The causative agents of the following invasive diseases of cyprinids were identified: dactylogyrosis, argulez, trichodinosis, diplozoonosis, piscicolez. For all detected parasites, a low intensity of invasion was noted (1–20 ind. per fish), which corresponds to the baseline values for pond rearing of Cyprinids and allows us to speak about satisfactory conditions for fish. The number of leeches averaged 10 specimens per fish, which is rather high in spring and indicates inadequate preparation of ponds for the fish-breeding season, or early arrival of spring; however, according to quantitative criteria, this corresponds to a low intensity of invasion. In general, the results obtained are consistent with the background presence of ectoparasites on cyprinids during pond rearing and allow us to speak about satisfactory conditions for keeping fish in the commercial farms of the Astrakhan region. The effect of earlier periods of the onset of high water temperatures in the river and ponds in recent years (2019–2020) on the development of the dynamics of invasive diseases in fish farms of the Astrakhan region requires additional study