engleski

Update on the distribution of freshwater crayfish in Croatia

Four indigenous European and two non-indigenous American freshwater crayfish species inhabit Croatian freshwater habitats. Generally, noble crayfish, narrow-clawed crayfish and stone crayfish are distributed in the water bodies of the Black Sea drainage while white-clawed crayfish inhabits rivers of the Adriatic Sea drainage. Non- indigenous species (signal crayfish and spiny-cheek crayfish) are distributed in the northern Croatia, 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. In this paper we present results of field work conducted from 2005 till 2010, and compare them with previous data. Approximately 480 sites were investigated. Results indicate that non-indigenous crayfish are spreading and displacing noble and narrow-clawed crayfish. No mass mortalities in the contact zone have been reported. This survey also revealed the spread of narrow-clawed crayfish westwards and southwards displacing noble and stone crayfish from their habitats. Stone and white-clawed crayfish populations undergo the biggest decline in numbers. Main reasons for this are disturbance of their habitats and intensive droughts which are pronounced lately. Collected data are helpful as a starting point for development of management strategies by state institutions dealing with protection of endangered crayfish species.

distribution; indigenous; non-indigenous; crayfish; Croatia

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