Hidrológiai Közlöny, 2017 (97. évfolyam)
2017 / 3. szám - TRANSNATIONAL EFFORTS - Sandu, Cristina - Dumitrache, Alina - Radu, Emilia - Dobre, Doru - Tudorache, Mädälina - Mihăilescu, Simona: The importance of good ecological status for the successful revival of Danube sturgeon
20 Hidrológiai Közlöny (Hungarian Journal of Hydrology) 2017. 97. évf. 3. sz. and competition with native species, to their burrowing activities inducing ecological damage to riverbanks or lakes, as well as to their ability to spread the crayfish plague, leading to the severe decline of native European crayfish species, (3) amphibians and reptiles, due to their capacity to outcompete native species through their breeding strategy, appetite and ability to disturb aquatic habitats, also posing a hazard to wildlife and human health due to the diseases they carry, (4) fish, with a significant negative impact especially on amphibians and other freshwater fish species, not only through predation and competition for food sources, but also through the disruption of the food webs and the transmission of diseases (5) semi-aquatic mammals, due to their ability to disrupt natural habitats and food webs, altering natural plant communities and fauna structure through their burrowing activities, reproduction strategy or voracious feeding behaviour. Considering their high impact at ecosystem level, measures to reduce their local impact and prevent their future expansion should be urgently taken in future management strategies, as they may severely affect the ecological status of the Danube water bodies, as well as the conservation status of protected species and habitats under the EU Birds and Habitats Directives and the Marine Strategy Framework Directive. In such situations, the IAS and water management measures should be further harmonized with the conservation measures for protected species/habitats taken under these directives. 18 of the worst invaders connected to the aquatic environment, occurring in the Danube countries, are briefly presented below {EC 2017): • Cabombacaroliniana (Carolina fanwort) - aquatic plant native to South America, brought to Europe as a decorative plant for aquariums, spreading rapidly due to its capacity to grow from tiny stem fragments to dense mats, clogging up lakes, ponds or water courses. The species is present in Danube countries such as Austria and Hungary. • Elodea nuttallii (Nuttall’s waterweed) - brought from North America for the aquarium trade, the species spread in slow flowing water bodies and lakes, being now present in Danube countries such as Austria, Bulgaria, Germany, Hungary, Romania, Slovakia and Slovenia. • Hydrocotyleranunculoides (Floating pennywort) - originally from America, this fast-growing aquatic plant was brought to Europe for aquariums and garden ponds. The species is present in Germany. • Lagarosiphon major (Curly waterweed) - native to South Africa, the species was introduced to Europe for aquariums. Of the Danube countries, the species is present in Austria, Germany, and Hungary. • • Ludwigia grandiflora (Water-primrose) - introduced from North America as an ornamental plant, it has established populations in European slow flowing rivers, streams, lakes and ponds. Besides its capacity to develop compact mats at the surface, blocking light and reducing oxygen content, it also has the ability to release alleo- pathic substances impairing the native species and affecting the entire ecosystem. It is already present in Germany and Hungary. • Myriophyllumaquaticum (Parrot’s feather) - originally from South America, the plant was brought for ornamental purposes and spread rapidly across the EU, being able to grow in lakes, ponds, wetlands, slow- running streams and canals. It is present in Austria, Germany, Hungary and Romania. • Myriophyllumheterophyllum (Broadleaf watermil- foil) - native to North America, this aquatic plant is able to grow in all types of aquatic ecosystems, including wetlands. It is already present in Austria, Germany and Hungary. • Eriocheirsinensis (Chinese mitten crab) - native to Eastern Asia, it probably entered Europe with ballast water, spreading rapidly from marine and brackish water to freshwater habitats. In the Danube countries, it is present in the Czech Republic, Germany, Hungary, Romania and Slovakia. • Orconecteslimosus (Spiny-cheek crayfish) - native to North America, it was introduced to Europe for farming, since then colonizing rivers, streams and lakes. It is present in Austria, Bulgaria, Croatia, Czech Republic, Germany, Hungary, Romania, Slovakia and Slovenia. • Pacifastacusleniusculus (Signal crayfish) — native to North America, it was introduced to Europe for farming, since then colonizing rivers, streams and lakes. It is present in Austria, Croatia, Czech Republic, Germany, Hungary, Slovakia and Slovenia. • Procambarusclarkii (Red swamp crayfish) - native to North America, this large crayfish species was brought to Europe for farming, having now spread in slow- flowing rivers, marshes, canals and lakes. It is present in Danube countries such as Austria and Germany. • Procambarusfallax f. virginalis (Marbled crayfish) - brought to Europe for aquariums, it is the only crayfish with the ability to clone itself. It is present in Croatia, the Czech Republic, Germany and Slovakia • Lithobatescatesbeianus (American bullfrog) - this large amphibian, native to North America, was brought to Europe for farming and pet stores, since then colonizing ponds, marshes and reservoirs. It is present in Germany and Slovenia. • Trachemysscripta (Red-eared, yellow-bellied and Cumberland sliders) - this large freshwater turtle originates from North America and has been brought to Europe for the pet trade. It is now present in several Danube countries: Austria, Bulgaria, Croatia, the Czech Republic, Germany, Hungary, Romania, Slovakia and Slovenia. • Perccottusglenii (Amur sleeper) - native to Asia, the species is especially widespread in Eastern Europe, being present in the Danube countries of Bulgaria, Croatia, Germany, Hungary, Romania and Slovakia.
