engleski

Invasive crustacean species in Croatian section of the Danube and Drava River

Within last several decades European rivers have been invaded by numerous non-indigenous species. As presence, distribution and impact of invasive aquatic species in Croatia is mostly unknown, a project aimed at determining invasive species status has recently been initiated at the Department of Zoology, Faculty of Science, University of Zagreb. This work presents initial results of the research on distribution of invasive crustacean fauna in Croatia. Research was conducted at 21 locations of the Croatian section of European second largest river, river Danube (10) and its tributary, river Drava (11). Baited LiNi traps and hand search were used for crayfish sampling and benthos nets for macrozoobenthos sampling. Literature data on invasive crustaceans in respective rivers in neighbouring countries were also gathered in order to detect potential records in bordering areas. Collected distribution data and a description of biology, invasion history and potential impact of recorded species are presented and discussed. Throughout our research we recorded one non-indigenous invasive decapod species (Orconectes limosus) and two invasive amphipod species (Dikerogammarus villosus and Dikerogammarus bispinosus). All three invasive crustaceans were found in Danube, while in Drava only D. villosus was recorded. As far as authors are aware, this is the first record of D. villosus in Drava, and most likely it spread from the Danube. It is assumed that at examined Danube sites, O. limosus has significantly displaced or reduced native narrow-clawed crayfish (Astacus leptodactylus) populations, since no narrow-clawed crayfish have been caught. Following the defined size classes for O. limosus, caught specimens were aged between 3 and 4 years, meaning that O. limosus population has been established in the area for at least 5 years. Since one of the records was only 3 kilometres downstream from the confluence with Drava, there is a potential risk of O. limosus spread to Drava watercourse.

invasive crustaceans; Croatia

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