Population structure and parasite fauna of stone moroko, Pseudorasbora parva (Temminck et Schlegel, 1846) in a watercourse of the Oder catchment area ('Central Plains' European Ecoregion)

The stone moroko (Pseudorasbora parva) is an invasive species which spreads rapidly in European water bodies and occupies free ecological niches. In the years 2019-2020, monthly analyses of its population structure were carried out in the Wardynka River (western Poland), determining the age, size (TL and SL), body weight, growth, Fulton's condition factor, and the parameters of the length-weight relationship. In addition, quantitative descriptions of the parasite communities were made. End-point PCR was used to verify the presence of Sphaerothecum destruens in the fish. The age structure of the population was dominated by fish at the age of 1+ to 3+, and the maximum age was 5 + . The TL of the fish ranged from 2.50 to 10.60 cm (average 6.24 cm), SL from 2.10 to 9.50 cm (average 5.20 cm), and body weight from 0.15 to 11.43 g (average 2.74 g). The average body weight and length of males were higher than in females. The average Fulton's condition factor for the whole sample was 1.44 & PLUSMN; 0.24 and was similar for both sexes. The slope of the regression line (b > 3) indicates an allometric relationship between the length and weight of fish of both sexes. Back-calculated estimates of standard length fitted the von Bertalanffy growth function, although Taylor's criterion showed that the asymptotic length (Linf) was overestimated. Comparison of the von Bertalanffy growth function parameters revealed differences between sexes. The presence of parasites not previously recorded in stone moroko in Poland was confirmed: Dactylogyrus squameus, Phyllodistomum elongatum, P. folium, Posthodiplostomum cuticola (metacercaria), and Bivalvia gen. sp. (glochidia). Electrophoresis of the end-point PCR product did not reveal any signs of amplification for either of the primer sets used. S. destruens was not detected in any of the analysed samples of stone moroko.

Automated summary

The stone moroko is an invasive species that rapidly spreads in European water bodies. In this study, population structure and parasite communities of stone moroko in the Wardynka River (western Poland) were analyzed. The fish were found to have a dominant age structure of 1+ to 3+, with a maximum age of 5+. The average size, weight, and condition factor varied between males and females. The presence of previously unrecorded parasites in stone moroko in Poland was confirmed, but the Sphaerothecum destruens parasite was not detected.