Invasion of the zebra mussel (Dreissena polymorpha) in a Dinaric karst river after formation of a new reservoir

Le résumé fourni par la source

The distribution and density of the zebra mussel, Dreissena polymorpha (Pallas, 1771), were studied from 2012–2017 in the Dobra River Basin, Croatia, where a new reservoir of Hydroelectric Power Plant Lešće was created in June 2010. The first zebra mussels were found in July 2012 in low density (38 ind.m-2) at a site 500 m downstream from the Lešće reservoir. In 2017 the density at this site had increased to 137 ind.m-2. The Lešće reservoir was colonized by zebra mussel from two upstream and connected reservoirs constructed in 1958. Maximum recorded density in the Lešće reservoir was 12, 496 ind.m- 2, with dominance of the smallest size categories. This population was the main source of propagules by which D. polymorpha colonized almost the whole remaining course of Gojačka Dobra through 2015. Most sites downstream from the dam showed increased densities from 2016 to 2017. The Lešće reservoir population should be monitored and managed as it represents the main “hotspot” of zebra mussels in the Dinaric karst area in Croatia from which other karst rivers could be invaded.

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