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The article presents the results of studies on the content of artificial (¹³⁷Cs, ⁹⁰Sr) and natural radionuclides (²²⁶Ra, ²³²Th, ⁴⁰K) in tissues and organs of various individuals of pumpkinseed Lepomis gibbosus (Linnaeus, 1758) from the Zaporizhzhia (Dnipro) reservoir. It has been revealed that in the bones of sexually mature pumpkinseed females, the content of radionuclides ¹³⁷Cs and⁹⁰Sr is 24.7% and 28.6% less, respectively, than in the bones of males. Summing up the materials of radioecological studies of 2017–2018, the following sequence of tissues and organs of the pumpkinseed by the ability to accumulate radionuclides was obtained: bone> muscle> scales> gills. Research results can be useful for further study on the fish radiation load in the basins of the Dnipro River and during monitoring radioecological research. It was determined that the content of radionuclides in the pumpkinseed muscles did not exceed the permissible levels of radionuclide content for fish as a food product (permissible levels of radionuclide content for ¹³⁷Cs – 150 Bq/kg, ⁹⁰Sr – 35 Bq/kg).
A total of 103 pumpkinseed sunfish L. gibbosus was surveyed for parasites. Fourteen parasite species representing six higher taxa were recovered. Of the fish examined, 72.8 % were found to harbour parasites. The most prevalent were glochidia of Unio sp. (43.7 %) and metacercariae of Diplostomum sp. (38:8 %). Findings of Ichthyocotylurus platycephalus, Tylodelphys clavata, Ergasilus sieboldi and Caligus lacustris constitute new host records. None of the species found, poses a human health threat.
To assess the current ecosystem status of Montedoglio Reservoir and surrounding waters, the fish fauna has been analysed in 1993, about five years after the first experimental impoundment. Total number of 898 fishes of fifteen species have been collected of the total biomass of 117 kg. The most abundant species were pumpkinseed (Lepomis gibbosus), goldfish (Carassius auratus L.), bleak (Alburnus alburnus alborella De Fil.), largemouth bass (Micropterus salmoides Lac.), rudd (Scardinius erythrophthalmus L.), and chub (Leuciscus cephalus L.), while the three: Carp (Cyprinus carpio L.), goldfish, and largemouth bass accounted for the most biomass. Of the most common species, carp, chub, largemouth bass and rudd provided insight into population structure and growth. In 1992, a year of heavy spring rains and a rapid water exchange, a year-class abundance across all species was particularly poor. The results of water levels and outflows between 1992-1994 showed a high degree of instability of the system. It appeared to favour fish species depositing their eggs inshore (i.e. chub) and predators (i.e. largemouth bass), while species with life stages feeding on plankton or benthos were not favoured.
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