Occurrence of topmouth gudgeon, Pseudorasbora parva, in relation to environmental factors in lowland streams and canals

Abstract

Abstract. Pseudorasbora parva is a non-native species that has long been established in Croatia and Europe and has been on the European list of Invasive Alien Species of Union concern since 2016. The species is known for its high invasiveness, negative impact on native species and rapid rate of spread, which is facilitated by its specific life history characteristics. Therefore, increased monitoring and control measures are needed to limit the spread of P. parva in Croatia and other European countries. This study aimed to investigate the current distribution of P. parva in lowland streams and canals of the River Sava basin and to determine environmental factors associated with its occurrence using Bernoulli Generalized Linear Model with an information theoretic approach. The species was found at 33 of 111 sampled sites where its occurrence was previously unknown. The model identified the absence of gravel in the substrate and a rich fish community as the best predictors of P. parva occurrence. Streams with natural water regimes and low numbers of specialised fish species are least likely to support the occurrence of this species, so such habitats should be protected from further alteration to be preserved as refugia for native ichthyofauna.