engleski

Update on the distribution of freshwater crayfish in Croatia

Four native European and two non-native American freshwater crayfish species inhabit Croatian freshwater habitats. In general, noble crayfish, narrow-clawed crayfish and stone crayfish are distributed in the water bodies belonging to the Black Sea drainage, while white-clawed crayfish inhabits rivers belonging to the Adriatic Sea drainage. Non-native species, namely signal crayfish and spiny-cheek crayfish, entered Croatia through the Mura River and the Danube River respectively, and so are distributed in the water bodies of the Black Sea drainage. Recently, the distribution of Croatian crayfish populations has been studied more intensely within the frame of Natura 2000, and in this paper we present results of field work that was conducted from 2008 till 2010, and compare them whit previous data. Approximately 400 sites were investigated. Results indicate that NICS are spreading and, expectedly, displacing noble and narrow-clawed crayfish populations. No mass mortalities in the contact zone have been reported. This survey also revealed spreading of narrow-clawed crayfish westwards and southwards displacing noble and stone crayfish from their original habitats. Stone and white-clawed crayfish populations undergo biggest decline in their numbers. Main reasons for this decline are disturbance of their habitats (water bodies’ construction-canalization, riverside vegetation removement etc.) and intensive droughts that are pronounced in the last few years. Collected data are helpful as a starting point for development of management strategies by state institutions dealing with protection of endangered native crayfish species.

indigenous; non-indigenous; distribution; protection; Croatia

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