The Perccottus glenii is one of the most invasive of European fish species. During August-September 2019, we examined Chinese sleeper from six waterbodies in Latvia and Ukraine for parasites. Seventeen parasite species were registered, including two ciliate species, one coccidia, one monogenean, one cestode, six trematodes, three nematodes, one acanthocephalan, one parasitic copepod, and one bivalve glochidia. Maximum species richness was registered in Ukraine, with eight species at Vylkove and three species at Lake Kartal. Numbers in Latvia were generally lower with three species at Ilgas and just one at Gailezers. The parasite fauna registered in Latvia was poor overall, the richest site being the University pond. Two non-native parasite species were registered, the monogenean Gyrodactylus perccotti and the copepod Neoergasilus japonicus. Gyrodactylus perccotti was observed in Lake Kartal and the Danube delta in Ukraine, but not in Latvia, while N. japonicus only occurred in the University Pond in Latvia. This is the first record of this species in Latvia. Low parasite acquisition by the Chinese sleeper in Latvia may be caused by the release of this fish from aquaria, which is commonly registered in the region. It is likely that such low parasite loads have contributed to the formation of stable populations and the subsequent increase in expansion.

According to recent data, fish fauna of the Oster River basin numbers 21 species, including two introduced species: Perccottus glenii and Pseudorasbora parva. 17 species of fish were registered in the lower section of the river (4 of them for the first time), 21 species were found in the middle section (12 of them were not previously noted for this section) and only 11 species were found in the upper section (6 species were not previously noted for this section). Six species-Pseudorasbora parva, Misgurnus fos silis, Pungitius platygaster, Gymnocephalus cernua, Babka gymnotrachelus and Protero rhinus semilunaris-are recordered in the Oster River for the first time. Fish population of the lower part differs by qualitative composition, primarily due to its link with the Desna River. Only 11 species were registered in three tributaries of the Oster River and in their basins. Nosivochka River has 6 species, including introduced Cyprinus carpio and Hypophthalmichthys molitrix. Five species were recorded in the Divytsia River basin and six species are found in the V'iunnytsia River. The most frequently caught species in the Oster River basin were Leucaspius delineatus and Rhodeus amarus (F = 75.0), Scardinius erythrophthalmus and Tinca tinca (F = 66.7).

No abstract

No abstract