Alien fishes in Hungary: the rise of aquarium species

In this study, we present an updated checklist of alien fish species occurring in Hungarian natural waters. In addition, by analyzing the taxonomic, original range, and spatio-temporal occurrence data of the species in question, we also present current invasion trends and distribution patterns. For the database compilation, we used literature reports, validated occurrence data published by non-research contributors (e.g., anglers), and our own unpublished faunistic data. The occurrence of species shows an exponentially increasing trend, with 89 out of the 130 registered species and hybrids appeared in the last 24 years. Most of the new species are thermophilic aquarium species, belonging to the orders Cichliformes (39%) and Siluriformes (29%). Recently, five species from the Anabantiformes order have emerged, posing a significant threat to the native fish fauna of Hungary. Spatial data analysis indicates that the most important introduction hotspots are currently found in some thermal habitats (mostly spa outflows), especially in the capital of Hungary (Budapest), and Lake Hévíz. Due to ongoing global warming, heat-impacted stream and river stretches may serve as starting points for new invasions in the near future. This assumption is supported by the recent distribution of toothcarps (Cyprinodontiformes), as their acclimatized stocks released from warmwater habitats are likely to overwinter in temperate water bodies as well.