The trade of live ornamental freshwater crayfi sh has grown rapidly in the last decade and has become the major pathway for new Non-Indigenous Crayfi sh Species (NICS) introductions into Europe (Chucholl et al. 2012). The parthenogenetic marbled crayfi sh or Marmorkrebs (Procambarus fallax f. virginalis) (Scholtz et al. 2003, Martin et al. 2010) had circulated in the European pet trade in laboratories since the 1990s (Vogt 2008, 2010, Faulkes 2010), and several years ago, the fi rst living samples were captured from natural European habitat (Soes and van Eekelen 2006). Since then, their known range is rapidly spreading in Central European countries, creating a new threat for European indigenous water ecosystems (Souty-Grosset et al. 2006, Chucholl and Daudey 2008, Chucholl 2011). People in Nordic European countries (especially Estonia) are concerned about the potential invasion of marble crayfi sh, because the Estonian Nature
1 Estonian University of Life Sciences, Institute of Veterinary Medicine and Animal Sciences, Department of Aquaculture, Kreutzwaldi 48, 51006 Tartu, Estonia.